Dr Suvash C Saha is a Senior Lecturer of Mechanical Engineering in the School of Mechanical and Mechatronic Engineering, University of Technology Sydney (UTS), Australia. He received his PhD in Computational Fluid Dynamics from James Cook University, Australia. Then he undertook Postdoctoral training at the Queensland University of Technology, Brisbane, Australia.
Dr Saha's current research activities focus on three key areas of (a) Computational Biomechanical Engineering which includes particle deposition, clearance and penetration into the lung surfactant, Red Blood Cell (RBC) deformation into the capillary vessels and aging effect on RBC deformation (b) Heat and Mass Transfer including Phase Change Materials (PCM), Solar thermal energy technology, Natural convection heat transfer in buildings and other confined geometries, Scale analysis for the transient flow, and (c) Microfluidics modelling including inertial separation techniques.
For more information see my personal website.
Can supervise: YES
Dr Saha's current research activities focus on three key areas of (a) Computational Biomechanical Engineering which includes particle deposition, clearance and penetration into the lung surfactant, Red Blood Cell (RBC) deformation into the capillary vessels and aging effect on RBC deformation (b) Heat and Mass Transfer including Phase Change Materials (PCM), Solar thermal energy technology, Natural convection heat transfer in buildings and other confined geometries, Scale analysis for the transient flow, and (c) Microfluidics modelling including inertial separation techniques.
For more information see my personal website.
1. Heat Transfer
2. Fluid Dynamics
3. Computational Fluid Dynamics
4. Dynamics of Machines.
5. Numerical Analysis
Bhowmick, S, Saha, SC, Qiao, M & Xu, F 2019, 'Transition to a chaotic flow in a V-shaped triangular cavity heated from below', INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, vol. 128, pp. 76-86.View/Download from: Publisher's site
Kuruneru, STW, Marechal, E, Deligant, M, Khelladi, S, Ravelet, F, Saha, SC, Sauret, E & Gu, Y 2019, 'A Comparative Study of Mixed Resolved–Unresolved CFD-DEM and Unresolved CFD-DEM Methods for the Solution of Particle-Laden Liquid Flows', Archives of Computational Methods in Engineering.View/Download from: Publisher's site
© 2018, CIMNE, Barcelona, Spain. The exorbitant economic and environmental cost associated with fouling propels the need to develop advanced numerical methods to accurately decipher the underlying phenomena of fouling and multiphase fluid transport in jet-engine fuel systems. Clogging of jet-fuel systems results in the foulants to settle in seconds to form a porous layer which restricts fuel flow. The objective of this research is to numerically examine the transient evolution of particle-laden liquid flow and particle accumulation on an idealized jet-fuel filter. This is achieved by using two numerical approaches: coupled unresolved computational fluid dynamics-discrete element method (CFD-DEM), and coupled mixed resolved–unresolved CFD-DEM method. We assess the efficacy of both numerical methods by comparing the numerical results against experimental data. Results have shown that the particle accumulation and deposition profiles are in good agreement with the experimental results. Moreover, it is found that the particle distribution spread along the length and height of the channel reflects the actual particle spread as observed in the experiments. The unresolved CFD-DEM and mixed resolved–resolved CFD-DEM method could be harnessed to study complex multiphase fluid flow transport in various other applications such as compact heat exchangers and fluidized beds.
Kuruneru, STW, Saha, SC, Sauret, E & Gu, YT 2019, 'Transient heat transfer and non-isothermal particle-laden gas flows through porous metal foams of differing structure', APPLIED THERMAL ENGINEERING, vol. 150, pp. 888-903.View/Download from: Publisher's site
Cui, H, Xu, F, Saha, SC & Liu, Q 2019, 'Transient free convection heat transfer in a section-triangular prismatic enclosure with different aspect ratios', International Journal of Thermal Sciences, vol. 139, pp. 282-291.View/Download from: Publisher's site
© 2019 Elsevier Masson SAS Free convection studies in a section-triangular prismatic enclosure with different aspect ratios (depth-width ratios, A) is conducted using three-dimensional numerical modeling approach. The Rayleigh number (Ra) covers a broad range from 10 0 to 10 7 . Transient free convection is characterized under top cooled and bottom heated boundary conditions. The flow structure of transverse rolls and longitudinal rolls is described. The critical Rayleigh numbers for the transition of the flow from driven by the baroclinic to Rayleigh-Bénard instability and from a steady to an unsteady state have been obtained for different aspect ratios. Free convection in the section-triangular prismatic enclosure could be divided into three regimes, which are presented in a Ra-A space. The quantitative relationship between heat transfer and the aspect ratio as well as the Rayleigh number has been obtained numerically.
Babayan, M, Mazraeh, AE, Yari, M, Niazi, NA & Saha, SC 2019, 'Hydrogen production with a photovoltaic thermal system enhanced by phase change materials, Shiraz, Iran case study', JOURNAL OF CLEANER PRODUCTION, vol. 215, pp. 1262-1278.View/Download from: UTS OPUS or Publisher's site
Taghilou, M, Sefidan, AM, Sojoudi, A & Saha, SC 2018, 'Solid-liquid phase change investigation through a double pipe heat exchanger dealing with time-dependent boundary conditions', Applied Thermal Engineering, vol. 128, pp. 725-736.View/Download from: UTS OPUS or Publisher's site
© 2017 Elsevier Ltd The use of phase change materials has been seriously recommended due to their high capacity of energy saving and delivering arising from phase change process. In addition, a constant temperature of melting or freezing provides a desirable condition to transfer a large amount of heat in a low-temperature fluctuation. This work attempts to present a numerical study to simulate the solid-liquid phase change considering a double pipe heat exchanger dealing with time-dependent boundary conditions. For this reason, a time dependent boundary condition of the third kind is applied. In a condition which the amplitude and periodicity of both bulk temperature and heat transfer coefficient (HTC) are varying in the sinusoidal form. The PCM container involves two separate sections to insert two different PCMs of RT28HC and RT35. In addition, in order to make up for the low thermal conductivity of PCMs, a porous medium with high thermal conductivity is located in PCM containers. Numerical model benefits the enthalpy-porosity approach based on the finite volume method, which models the phase change in the fixed grid domain. Moreover, in order to accurate simulation, fluid flow arising from Boussinesq approximation in the liquid phase is also considered using PISO algorithm. According to the results, the arrangement of RT35 in section A and RT28HC in section B accelerates the system response to the boundary oscillation. In addition, increasing the periodicity of the bulk temperature variation increases the amount of phase changing process in both sections while varying the same parameter of HTC does not influence the liquid fraction of PCMs considerably.
Zhai, H, Xu, F, Saha, SC & Hou, Y 2018, 'Natural convection and heat transfer on a section-triangular roof', International Communications in Heat and Mass Transfer, vol. 92, pp. 23-30.View/Download from: UTS OPUS or Publisher's site
© 2018 Elsevier Ltd Natural convection and heat transfer on a section-triangular roof are common around buildings. In this study, the slope flow and the plume on the suddenly heated section-triangular roof are investigated using scaling analysis and numerical simulation. The dynamics and heat transfer are discussed. It has been demonstrated that there exist different regimes of transient natural convection on the roof, which depends on the Rayleigh number, the aspect ratio of the roof and the Prandtl number. The scaling laws in different scenarios including inertial and viscous regimes are obtained and verified by numerical results. There is agreement between the scaling laws and numerical results. Further, the formulae of heat transfer and natural convection on the roof are presented.
Bhowmick, S, Xu, F, Zhang, X & Saha, SC 2018, 'Natural convection and heat transfer in a valley shaped cavity filled with initially stratified water', International Journal of Thermal Sciences, vol. 128, pp. 59-69.View/Download from: UTS OPUS or Publisher's site
© 2018 Elsevier Masson SAS Fog is omnipresent in the natural environment, namely valleys and mountains. A strong comprehension of the fluid flow dynamics pertaining to fog formation is of crucial importance. In the present study, the two-dimensional numerical method is used to investigate the transient natural convection in a valley-shaped triangular cavity initially filled with stratified water. A wide range of Rayleigh numbers (2.26 × 105–2.26 × 109) and aspect ratios (0.1–1.0) are considered. The numerical results are verified against experimental results. The development of natural convection flows in the cavity from the start up to the steady state is classified into two stages: an early stage and a transitional stage. Transient natural convection flows in the cavity are described. Spectral analysis is performed for different governing parameters. A simple scaling analysis is performed for the thermal boundary layer and the time scale of the stratification breakup describing the disappearance of fog in the valley is obtained and validated by numerical results. Additionally, mass and heat transfer in the cavity is measured and the scaling relation between the Nusselt number and the Rayleigh number for different aspect ratios are presented.
Kuruneru, STW, Sauret, E, Saha, SC & Gu, YT 2018, 'Coupled CFD-DEM simulation of oscillatory particle-laden fluid flow through a porous metal foam heat exchanger: Mitigation of particulate fouling', Chemical Engineering Science, vol. 179, pp. 32-52.View/Download from: UTS OPUS or Publisher's site
© 2018 Elsevier Ltd A coupled finite volume-discrete element (FVM-DEM) numerical method is developed to investigate oscillating multiphase foulant-laden air (solid-gas) flow and particulate fouling in a porous heat exchanger channel comprising an array of circular cylinders. Oscillatory fluids serve as a steppingstone to advance existing conventional anti-fouling techniques and to yield optimum energy consumption. A performance evaluation criteria based on various amplitudes of pulsation and foulant injection rates is established. The fouling characteristics and pressure drop is compared against a non-oscillating steady flow. For the solid foulant particles considered in this study, the results show that the time-averaged deposition fraction is sensibly invariant with increasing foulant injection rate; however, the same observation is not realized for steady-flow cases. The 1 Hz case showed no significant disparity in terms of deposition fraction at high injection rates compared with the non-oscillating steady flow case. In addition, the 1 Hz case showed miniscule reduction of low-density foulants. The higher-frequency spectrum has superior fouling mitigation capabilities although comparatively higher pressure drop is generated. The 6-pore configuration outperforms the 3-pore under certain oscillatory flow conditions. An optimum frequency of 5 Hz exhibits superior fouling mitigation performance while achieving a low time-averaged pressure drop.
Polwaththe-Gallage, HN, Sauret, E, Nguyen, NT, Saha, SC & Gu, Y 2018, 'A novel numerical model to predict the morphological behavior of magnetic liquid marbles using coarse grained molecular dynamics concepts', Physics of Fluids, vol. 30, no. 1.View/Download from: UTS OPUS or Publisher's site
© 2018 Author(s). Liquid marbles are liquid droplets coated with superhydrophobic powders whose morphology is governed by the gravitational and surface tension forces. Small liquid marbles take spherical shapes, while larger liquid marbles exhibit puddle shapes due to the dominance of gravitational forces. Liquid marbles coated with hydrophobic magnetic powders respond to an external magnetic field. This unique feature of magnetic liquid marbles is very attractive for digital microfluidics and drug delivery systems. Several experimental studies have reported the behavior of the liquid marbles. However, the complete behavior of liquid marbles under various environmental conditions is yet to be understood. Modeling techniques can be used to predict the properties and the behavior of the liquid marbles effectively and efficiently. A robust liquid marble model will inspire new experiments and provide new insights. This paper presents a novel numerical modeling technique to predict the morphology of magnetic liquid marbles based on coarse grained molecular dynamics concepts. The proposed model is employed to predict the changes in height of a magnetic liquid marble against its width and compared with the experimental data. The model predictions agree well with the experimental findings. Subsequently, the relationship between the morphology of a liquid marble with the properties of the liquid is investigated. Furthermore, the developed model is capable of simulating the reversible process of opening and closing of the magnetic liquid marble under the action of a magnetic force. The scaling analysis shows that the model predictions are consistent with the scaling laws. Finally, the proposed model is used to assess the compressibility of the liquid marbles. The proposed modeling approach has the potential to be a powerful tool to predict the behavior of magnetic liquid marbles serving as bioreactors.
Qiao, M, Xu, F & Saha, SC 2018, 'Numerical study of the transition to chaos of a buoyant plume from a two-dimensional open cavity heated from below', APPLIED MATHEMATICAL MODELLING, vol. 61, pp. 577-592.View/Download from: UTS OPUS or Publisher's site
Mazraeh, AE, Babayan, M, Yari, M, Sefidan, AM & Saha, SC 2018, 'Theoretical study on the performance of a solar still system integrated with PCM-PV module for sustainable water and power generation', Desalination, vol. 443, pp. 184-197.View/Download from: UTS OPUS or Publisher's site
© 2018 Elsevier B.V. Current paper studies a new solar still system integrated with semitransparent photovoltaic, evacuated tube collectors and phase change materials. Mathematical modeling has been accomplished based on energy/exergy balance equations to investigate the effects of various PCM-PV modules, basin water depth and tube numbers on the system thermal and electrical performance. The system is examined in terms of distilled water production, electricity generation, and energy/exergy efficiencies. Variations of distilled water, system temperature, generated electricity power and energy/exergy outputs and efficiencies over time are presented for various effective parameters. Considering obtained results, while PV type does not affect distilled water, it is the dominant parameter on generated electrical power. Tube number as another important parameter, improves the distilled water production, however, it influences the energy/exergy efficiencies in an inverse way. Presence of PCM, improves the energy efficiency, but has negligible effect on the exergy efficiency. The highest amount of distilled water during a day is calculated for the water basin depth of 0.03 m and 30 tube number with paraffin wax PCM type (4.5503 kg/m2·day) which is 20.32% more than the case without PCM. Moreover, maximum diurnal energy/exergy efficiencies are reported 17.93% and 6.95% for water depth of 0.03 m and 10 tubes with PCM.
Islam, MS, Saha, SC, Gemci, T, Yang, IA, Sauret, E & Gu, YT 2018, 'Polydisperse Microparticle Transport and Deposition to the Terminal Bronchioles in a Heterogeneous Vasculature Tree', SCIENTIFIC REPORTS, vol. 8.View/Download from: Publisher's site
Qiao, M, Xu, F & Saha, SC 2017, 'Scaling analysis and numerical simulation of natural convection from a duct', NUMERICAL HEAT TRANSFER PART A-APPLICATIONS, vol. 72, no. 5, pp. 355-371.View/Download from: UTS OPUS or Publisher's site
Ma, Y, Saha, SC, Miller, W & Guan, L 2017, 'Parametric Analysis of Design Parameter Effects on the Performance of a Solar Desiccant Evaporative Cooling System in Brisbane, Australia', ENERGIES, vol. 10, no. 7.View/Download from: UTS OPUS or Publisher's site
Islam, MS, Saha, SC, Sauret, E, Gemci, T, Yang, IA & Gu, YT 2017, 'Ultrafine particle transport and deposition in a large scale 17-generation lung model.', Journal of Biomechanics, vol. 64, pp. 16-25.View/Download from: UTS OPUS or Publisher's site
To understand how to assess optimally the risks of inhaled particles on respiratory health, it is necessary to comprehend the uptake of ultrafine particulate matter by inhalation during the complex transport process through a non-dichotomously bifurcating network of conduit airways. It is evident that the highly toxic ultrafine particles damage the respiratory epithelium in the terminal bronchioles. The wide range of in silico available and the limited realistic model for the extrathoracic region of the lung have improved understanding of the ultrafine particle transport and deposition (TD) in the upper airways. However, comprehensive ultrafine particle TD data for the real and entire lung model are still unavailable in the literature. Therefore, this study is aimed to provide an understanding of the ultrafine particle TD in the terminal bronchioles for the development of future therapeutics. The Euler-Lagrange (E-L) approach and ANSYS fluent (17.2) solver were used to investigate ultrafine particle TD. The physical conditions of sleeping, resting, and light activity were considered in this modelling study. A comprehensive pressure-drop along five selected path lines in different lobes was calculated. The non-linear behaviour of pressure-drops is observed, which could aid the health risk assessment system for patients with respiratory diseases. Numerical results also showed that ultrafine particle-deposition efficiency (DE) in different lobes is different for various physical activities. Moreover, the numerical results showed hot spots in various locations among the different lobes for different flow rates, which could be helpful for targeted therapeutical aerosol transport to terminal bronchioles and the alveolar region.
Islam, MS, Saha, SC, Sauret, E, Gemci, T & Gu, YT 2017, 'Pulmonary aerosol transport and deposition analysis in upper 17 generations of the human respiratory tract', Journal of Aerosol Science, vol. 108, pp. 29-43.View/Download from: UTS OPUS or Publisher's site
© 2017 Elsevier Ltd The major problem in understanding the therapeutically targeted drug delivery system in the deeper airways of the human lung is the lack of adequate data of particle transport and deposition (TD) in the transitional and respiratory zones (deeper airways) of the human lung. An understanding of the morphometry of the pulmonary airways and the lungs forms the primary step in a study of pulmonary aerosol deposition. The present study is the first-ever approach to explore the pulmonary aerosol TD in a digital 17-generation human pulmonary airway model. The present numerical study achieved the lack of the particle TD data in the deeper airways of the human lung. This paper presents a 3-D (3-dimensional) CFD (Computational Fluid Dynamics) study of an anatomically realistic 17-generation lung bronchial tree model based on the high-resolution computer tomography (HRCT) data by Schmidt et al. (2004). Physical morphometry is necessary for sufficiently calculating air and particle dynamics in human pulmonary airways with available data on a large number of generations. A Lagrangian-based Discrete Phase Model (DPM) is used to study the particle TD in the 17-generation of the lung airways. The numerical results demonstrate that inertial impaction is dominant in the upper airways and a large percentage of particles is deposited in the upper airways. The numerical results also illustrate that a large percentage of smaller diameter particles leaves through the airway outlet boundary at the 17th generation irrespective of breathing patterns. The escaped particles are considered to continue to follow the airway flow field further downstream after the 17th generation till the 23rd generation and some of them will reach the alveolar sacs region. This computational model could potentially aid in overcoming the nanobiotechnology toxicity problem for drug delivery in the deeper airways.
Sefidan, AM, Sojoudi, A & Saha, SC 2017, 'Nanofluid-based cooling of cylindrical lithium-ion battery packs employing forced air flow', International Journal of Thermal Sciences, vol. 117, pp. 44-58.View/Download from: UTS OPUS or Publisher's site
© 2017 Elsevier Masson SAS Efficient cooling strategies are very important issues in thermal management of lithium-Ion battery system and these techniques should provide cost effective and energy saving solutions for temperature rise of the system during battery operation. A pseudo 2D electrochemical model has been used to investigate the electrochemical and thermal condition of commercial 18650 Lithium-Ion battery. This analysis was compared to previous experimental studies and results showed that the model predicts the temperature rise and thermal power generation very well. Results from the electro-thermal analysis were used to examine a cooling method. In this strategy, the cylindrical Li-ion cell is submersed within a thin cylindrical tank containing water-Al 2 O 3 nanofluid. Air flow is employed to remove the heat from the system during discharge process. After testing this method for a single cell with various sizes of the secondary cylinder, critical and thermally dangerous arrangements of Li-ion cells were analyzed employing the new technique. 3D transient Computational Fluid Dynamics (CFD) simulations were used to see the effect of presence of the secondary cylinder on temperature rise. Results revealed that the new method reduces the maximum temperature of the cells efficiently.
Ma, Y, Saha, SC, Miller, W & Guan, L 2017, 'Comparison of Different Solar-Assisted Air Conditioning Systems for Australian Office Buildings', ENERGIES, vol. 10, no. 10.View/Download from: UTS OPUS or Publisher's site
Kuruneru, STW, Sauret, E, Saha, SC & Gu, Y 2017, 'A Novel Experimental Method to Assess Particle Deposition in Idealized Porous Channels', HEAT TRANSFER ENGINEERING, vol. 38, no. 11-12, pp. 1008-1017.View/Download from: UTS OPUS or Publisher's site
Kuruneru, STW, Sauret, E, Saha, SC & Gu, YT 2017, 'A coupled finite volume & discrete element method to examine particulate foulant transport in metal foam heat exchangers', International Journal of Heat and Mass Transfer, vol. 115, pp. 43-61.View/Download from: UTS OPUS or Publisher's site
© 2017 Elsevier Ltd The exorbitant costs associated with particulate fouling necessitates the need to formulate advanced methods to comprehend mass transport and fouling in heat exchangers. A coupled finite volume and discrete element method is developed to investigate the mechanisms that govern particle-laden gas flows and particulate fouling in idealized porous metal foam heat exchangers. This meticulous examination will take great precedence in addressing the negative impact particulate fouling has in the industry. The numerical method will permit engineers to better optimize porous metal foams for applications such as air-cooled heat aluminium heat exchangers. The robustness of this numerical method is validated against the original and modified Darcy-Forchheimer analytical equations through a novel modified porosity theory. Good agreement is obtained between the numerical and analytical results. It is shown that both 2D and 3D heat exchanger configurations of identical porosities with different geometric profiles have shown similar deposition fraction and pressure drop magnitudes albeit having a slightly different fouling layer distribution. This is attributable to the particle properties and the variation between the 2D and 3D inlet injection plane surface area. It is found that the commencement of sandstone and sawdust deposition in a 6-pore configuration differs by 0.57 s, whereas a three pore configuration completely nullifies particulate fouling irrespective of foulant type. A staggered row configuration has shown significant reduction in pressure drop as compared to the 6-pore heat exchanger configuration. For the case of sandstone particles, the optimum heat exchanger geometry exhibits 78% less pressure drop and 100% less deposition fraction compared with the original 6-pore configuration.
Cui, H, Xu, F & Saha, SC 2017, 'Transition to unsteady natural convection flow in a prismatic enclosure of triangular section', International Journal of Thermal Sciences, vol. 111, pp. 330-339.View/Download from: UTS OPUS or Publisher's site
© 2016 Elsevier Masson SAS Natural convection in a prismatic enclosure of triangular section with the top cooling and the bottom heating is investigated using three dimensional (3D) numerical simulations for a wide range of Rayleigh numbers from 10 0 to 1.25 × 10 6 . The numerical result has been compared with the experiment. The development of natural convection flows in the cavity following sudden heating and cooling involves three stages: an initial stage, a transitional stage and a fully developed stage. Transition to unsteady natural convection flow in the fully developed stage, dependent on the Rayleigh number, is described. The flow structure including transversal and longitudinal rolls is characterized and the corresponding mechanism is discussed. The critical Rayleigh number for the transition to unsteady natural convection flow is obtained. The dependence of heat transfer on the Rayleigh number is quantified.
Sefidan, AM, Sojoudi, A, Saha, SC & Cholette, M 2017, 'Multi-layer PCM solidification in a finned triplex tube considering natural convection', Applied Thermal Engineering, vol. 123, pp. 901-916.View/Download from: UTS OPUS or Publisher's site
© 2017 Elsevier Ltd Efficient latent heat storage systems represent an important opportunity to improve the thermal performance and operational capability of industrial systems (e.g. solar thermal). In this paper, numerical study is performed to evaluate the heat transfer and solidification features, phase change period and temperature distribution of double-layer Phase Changing Materials (PCM) in a finned triplex tube. A two-dimensional finite volume numerical technique is used to solve the governing equations considering conduction and convection heat transfer mechanisms at a fixed Rayleigh number of 10 6 . After comparing the results for single and double layer configurations, possible arrangements of two different PCMs are discussed in terms of different thicknesses of each PCM, fin sizes and different heat transfer fluid temperatures. Results are illustrated as the form of temperature, liquid fraction, stream function and velocity magnitude contours and their changes over the freezing time. Variation of liquid fraction values, average and minimum temperatures of layers in a double-layer PCM are reported for better insight into the heat transfer features of the latent heat thermal energy storage system to enable uniform discharging designs and balance the phase changing rate within the whole annulus.
Kuruneru, STW, Sauret, E, Vafai, K, Saha, SC & Gu, Y 2017, 'Analysis of particle-laden fluid flows, tortuosity and particle-fluid behaviour in metal foam heat exchangers', CHEMICAL ENGINEERING SCIENCE, vol. 172, pp. 677-687.View/Download from: UTS OPUS or Publisher's site
Ma, J, Xu, F & Saha, SC 2017, 'Flows and heat transfer of the transition to an unsteady state in a finned cavity for different Prandtl numbers', International Communications in Heat and Mass Transfer, vol. 88, pp. 220-227.View/Download from: UTS OPUS or Publisher's site
© 2017 Elsevier Ltd Flows and heat transfer of the transition to an unsteady state in a finned cavity are studied for Prandtl numbers (Pr) from 0.1 to 100 and Rayleigh numbers (Ra) from 10 7 to 10 10 . Transient flows are described in the finned cavity. Critical Rayleigh numbers of the transition to an unsteady state are obtained for different Prandtl numbers and the relation between two dimensionless parameters is given. The spectral analysis is applied for the oscillations of unsteady flows and the dominant frequency dependent on governing parameters is presented. Heat transfer of the transition to an unsteady flow is quantified and the corresponding relations dependent on the Prandtl number and Rayleigh number are gained. It is demonstrated that the flow rate and the Nusselt number of the finned cavity significantly increase due to the presentence of the fin, which depend on the Prandtl number and the Rayleigh number.
From, CS, Sauret, E, Armfield, SW, Saha, SC & Gu, YT 2017, 'Turbulent dense gas flow characteristics in swirling conical diffuser', Computers and Fluids, vol. 149, pp. 100-118.View/Download from: UTS OPUS or Publisher's site
© 2017 Elsevier Ltd Diffusers placed at the exit of turbines are essential to recover pressure and increase turbine efficiency. This increase of efficiency is critical for the overall cycle efficiency of renewable power cycles based on low temperature renewable resources. Optimising the performance of a conical diffuser in renewable power cycles using high-density fluids can be established by examining the turbulence characteristics of both air considered as an ideal gas (IG) and R143a, a refrigerant with high-density in a non-ideal state, considered as a real gas (RG). Turbulence was firstly modelled and validated against experimental results from the ERCOFTAC swirling conical diffuser database and previous numerical results. The real gas thermodynamic and transport properties of refrigerant R143a were then obtained from the NIST REFPROP database. Investigating both RG and IG revealed that general trends remain, where the stronger wall components in RG help improve the diffuser performance. Furthermore, investigations regarding turbulence intensities indicated a clear effect on the flow behaviour for IG while being ineffective on the RG. The final application analysed the diffuser performance using the inlet conditions extracted directly from a potential radial-inflow turbine working with R143a. The change of conditions highlighted that radial components can be reduced, and thus the swirling number too. By implementing the first numerical study on real gas swirling conical diffuser, it was established that real gas flow regimes differ from the ones previously established for ideal gas, and thus preliminary flow regimes for R143a, specifically, are proposed.
Barns, S, Balanant, MA, Sauret, E, Flower, R, Saha, S & Gu, Y 2017, 'Investigation of red blood cell mechanical properties using AFM indentation and coarse-grained particle method', BIOMEDICAL ENGINEERING ONLINE, vol. 16.View/Download from: UTS OPUS or Publisher's site
Kuruneru, STW, Sauret, E, Saha, SC & Gu, YT 2017, 'Two- and four-way coupling of cohesive poly-disperse particulate foulants on a metal foam fibre immersed in quiescent fluid', International Communications in Heat and Mass Transfer, vol. 89, pp. 176-184.View/Download from: UTS OPUS or Publisher's site
© 2017 Elsevier Ltd The ubiquity and complexity of the unsteadiness of fouling and multiphase flows in various engineering systems signify the need to develop advanced numerical methods to study the underlying phenomena of two-phase particle-laden fluid flows in heat exchanger systems such as, compact electronics cooling (i.e. heat sinks) and HVAC & R systems. Fouling is omnipresent in many industries such as power generation, chemical, petroleum, among others. The mechanisms governing fouling coupled with multiphase foulant-laden fluid flow in porous heat exchangers, such as metal foams, are very complex and poorly understood. This investigation forms the basis for addressing the implications of fouling for a myriad of industrial processes. This study will discuss the development of a coupled finite volume method and discrete element method (FVM-DEM) numerical framework to investigate the mechanisms governing particulate fouling in an idealized metal foam heat exchanger. This study resolves four-way and two-way coupled interactions based on poly-disperse cohesive foulants in fluid-saturated foam. The significance stems from the inclusion of cohesiveness between particle-particle and particle-wall contacts which play a decisive role in the foulant aggregation process prevalent in particles with a diameter smaller than 50 m. The present results show that the cohesive foulants exhibit strong tendency to aggregate with time and form chain-like projections. A rigid aggregate stack is formed which alters the fluid velocity of the fluid-filled foam. Quantitative analysis of the foulant count and time-averaged aggregate count is discussed. The presented results and the numerical framework could potentially be used to optimize heat exchanger designs by considering operating conditions and foam morphology (i.e. pore diameter, ligament thickness, porosity) that is most susceptible to particulate fouling.
Polwaththe-Gallage, H-N, Saha, SC, Sauret, E, Flower, R, Senadeera, W & Gu, Y 2016, 'SPH-DEM approach to numerically simulate the deformation of three-dimensional RBCs in non-uniform capillaries', BIOMEDICAL ENGINEERING ONLINE, vol. 15.View/Download from: UTS OPUS or Publisher's site
Sojoudi, A, Saha, SC, Sefidan, AM & Gu, YT 2016, 'Natural convection subject to sinusoidal thermal forcing on inclined walls and heat source located on bottom wall of an attic-shaped space', Energy and Buildings, vol. 128, pp. 845-866.View/Download from: Publisher's site
© 2016 Elsevier B.V. Natural convection within an attic space under diurnal temperature condition on the sloping wall and a heat source located on the insulated bottom wall have been studied to show the basic flow features in the attic space over diurnal cycles. The finite volume numerical method has been employed to solve the governing equations. Effect of Rayleigh number (Ra), attic aspect ratio, heater location and its size are discussed on the transient flow pattern and heat transfer phenomenon after grid independency and time interval selection tests with a fixed prandtl number of 0.72 (air). Results are presented as a form of isotherms and streamlines. Also, heat transfer is presented as a form of Nusselt number. The numerical experiments show that, the flow in the attic space is stratified during the daytime heating stage; whereas the flow becomes unstable at the night-time cooling stage.
Sojoudi, A, Khezerloo, M, Saha, SC & Gu, Y 2016, 'Effect of rotating cylinder on heat transfer in a differentially heated rectangular enclosure filled with power law non-Newtonian fluid', INTERNATIONAL JOURNAL OF NUMERICAL METHODS FOR HEAT & FLUID FLOW, vol. 26, no. 6, pp. 1910-1931.View/Download from: Publisher's site
Mojumder, S, Rabbi, KM, Saha, S, Hasan, MN & Saha, SC 2016, 'Magnetic field effect on natural convection and entropy generation in a half-moon shaped cavity with semi-circular bottom heater having different ferrofluid inside', JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, vol. 407, pp. 412-424.View/Download from: Publisher's site
Sojoudi, A, Saha, SC, Xu, F & Gu, YT 2016, 'Transient air flow and heat transfer due to differential heating on inclined walls and heat source placed on the bottom wall in a partitioned attic shaped space', Energy and Buildings, vol. 113, pp. 39-50.View/Download from: Publisher's site
© 2015 Elsevier B.V. All rights reserved. Numerical simulations are carried out to study the unsteady air flow and heat transfer in a partitioned triangular cavity of differentially heated from inclined walls and heat source placed at the bottom wall. The finite volume numerical method has been employed to solve the governing equations. The grid sensitivity test has been carried out and obtained results have been validated against experimental results. The dependency of several parameters on fluid flow and heat transfer is studied including Rayleigh number from 103 to 106, heater size from 0.2 to 0.6, heater position from 0.3 to 0.7 and aspect ratio from 0.2 to 1.0 with a fixed Prandtl number of 0.72 (air). A conductive partition of infinite conductivity is placed at the middle of the enclosure, which means that only heat can freely transfer between two fluid zones through the partition. Results are presented as a form of isotherms and streamlines. Also, heat transfer is presented as a form of Nusselt number. Both transient and steady states of solutions are presented in this study.
Kuruneru, STW, Sauret, E, Saha, SC & Gu, Y 2016, 'Numerical investigation of the temporal evolution of particulate fouling in metal foams for air-cooled heat exchangers', APPLIED ENERGY, vol. 184, pp. 531-547.View/Download from: Publisher's site
Polwaththe-Gallage, H-N, Saha, SC, Sauret, E, Flower, R & Gu, Y 2016, 'A coupled SPH-DEM approach to model the interactions between multiple red blood cells in motion in capillaries', INTERNATIONAL JOURNAL OF MECHANICS AND MATERIALS IN DESIGN, vol. 12, no. 4, pp. 477-494.View/Download from: Publisher's site
Ul Islam, S, Rahman, H, Ying, ZC & Saha, SC 2016, 'Comparison of wake structures and force measurements behind three side-by-side cylinders', JOURNAL OF THE BRAZILIAN SOCIETY OF MECHANICAL SCIENCES AND ENGINEERING, vol. 38, no. 3, pp. 843-858.View/Download from: Publisher's site
Siddiki, MN-A-A, Molla, MM & Saha, SC 2016, 'Natural Convection Flow in Porous Enclosure with Localized Heating From Below with Heat Flux', PROCEEDINGS OF THE 11TH INTERNATIONAL CONFERENCE ON MECHANICAL ENGINEERING (ICME 2015), vol. 1754.View/Download from: Publisher's site
Islam, SU, Rahman, H, Abbasi, WS, Saha, SC & Shahina, T 2016, 'Numerical investigation of flow past a row of rectangular rods', ALEXANDRIA ENGINEERING JOURNAL, vol. 55, no. 3, pp. 2351-2365.View/Download from: Publisher's site
Bovand, M, Rashidi, S, Esfahani, JA, Saha, SC, Gu, YT & Dehesht, M 2016, 'Control of flow around a circular cylinder wrapped with a porous layer by magnetohydrodynamic', Journal of Magnetism and Magnetic Materials, vol. 401, pp. 1078-1087.View/Download from: Publisher's site
© 2015 Published by Elsevier B.V. The present study focuses on the analysis of two-dimensional Magnetohydrodynamic (MHD) flow past a circular cylinder wrapped with a porous layer in different laminar flow regimes. The Darcy-Brinkman-Forchheimer model has been used for simulating flow in porous medium using finite volume based software, Fluent 6.3. In order to analyze the MHD flow, the mean and instantaneous drag and lift coefficients and stream patterns are computed to elucidate the role of Stuart number, N and Darcy number, Da. It is revealed that the magnetic fields are capable to stabilize flow and suppress the vortex shedding of vortices. The N-Re plane shows the curves for separating steady and periodic flow regimes, Ncr and disappearing of vortex, Ndiss. For validate the solution, the obtained CD and St are compared with available results of literature.
Hussain, S, Roy, NC, Hossain, MA & Saha, SC 2015, 'Effect of Fluctuating Surface Heat and Mass Flux on Natural Convection Flow along a Vertical Flat Plate', MATHEMATICAL PROBLEMS IN ENGINEERING.View/Download from: Publisher's site
Cui, H, Xu, F & Saha, SC 2015, 'A three-dimensional simulation of transient natural convection in a triangular cavity', INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, vol. 85, pp. 1012-1022.View/Download from: Publisher's site
Siddiqa, S, Hossain, MA & Saha, SC 2015, 'Two-phase natural convection flow of a dusty fluid', INTERNATIONAL JOURNAL OF NUMERICAL METHODS FOR HEAT & FLUID FLOW, vol. 25, no. 7, pp. 1542-1556.View/Download from: Publisher's site
Polwaththe-Gallage, H-N, Saha, SC, Sauret, E, Flower, R & Gu, Y 2015, 'Numerical Investigation of Motion and Deformation of a Single Red Blood Cell in a Stenosed Capillary', INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS, vol. 12, no. 4.View/Download from: Publisher's site
Rahman, H, Shams-Ul-Islam, Ying, ZC, Kiyani, T & Saha, SC 2015, 'On the effect of Reynolds number for flow past three side-by-side square cylinders for unequal gap spacings', KSCE JOURNAL OF CIVIL ENGINEERING, vol. 19, no. 1, pp. 233-247.View/Download from: Publisher's site
Sojoudi, A, Saha, SC & Gu, YT 2015, 'Natural convection due to differential heating of inclined walls and heat source placed on bottom wall of an attic shaped space', Energy and Buildings, vol. 89, pp. 153-162.View/Download from: Publisher's site
© 2014 Elsevier B.V. All rights reserved. Numerical investigation of free convection heat transfer in an attic shaped enclosure with differentially heated two inclined walls and filled with air is performed in this study. The left inclined surface is uniformly heated whereas the right inclined surface is uniformly cooled. There is a heat source placed on the right side of the bottom surface. Rest of the bottom surface is kept as adiabatic. Finite volume based commercial software ANSYS 15 (Fluent) is used to solve the governing equations. Dependency of various flow parameters of fluid flow and heat transfer is analyzed including Rayleigh number, Ra ranging from 103 to 106, heater size from 0.2 to 0.6, heater position from 0.3 to 0.7 and aspect ratio from 0.2 to 1.0 with a fixed Prandtl number of 0.72. Outcomes have been reported in terms of temperature and stream function contours and local Nusselt number for various Ra, heater size, heater position, and aspect ratio. Grid sensitivity analysis is performed and numerically obtained results have been compared with those results available in the literature and found good agreement.
Saha, SC & Gu, YT 2015, 'Natural convection in a triangular enclosure heated from below and non-uniformly cooled from top', INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, vol. 80, pp. 529-538.View/Download from: Publisher's site
Saha, SC, Khan, MMK & Gu, YT 2014, 'Unsteady buoyancy driven flows and heat transfer through coupled thermal boundary layers in a partitioned triangular enclosure', International Journal of Heat and Mass Transfer, vol. 68, pp. 375-382.View/Download from: Publisher's site
A numerical investigation has been carried out for the coupled thermal boundary layers on both sides of a partition placed in an isosceles triangular enclosure along its middle symmetric line. The working fluid is considered as air which is initially quiescent. A sudden temperature difference between two zones of the enclosure has been imposed to trigger the natural convection. It is anticipated from the numerical simulations that the coupled thermal boundary layers development adjacent to the partition undergoes three distinct stages; namely an initial stage, a transitional stage and a steady state stage. Time dependent features of the coupled thermal boundary layers as well as the overall natural convection flow in the partitioned enclosure have been discussed and compared with the non-partitioned enclosure. Moreover, heat transfer as a form of local and overall average Nusselt number through the coupled thermal boundary layers and the inclined walls is also examined. © 2013 Elsevier Ltd. All rights reserved.
Ismail, F, Hasan, MN & Saha, SC 2014, 'Numerical study of turbulent fluid flow and heat transfer in lateral perforated extended surfaces', ENERGY, vol. 64, pp. 632-639.View/Download from: Publisher's site
Bhowmick, S, Molla, MM, Mia, M & Saha, SC 2014, 'Non-Newtonian Mixed Convection Flow from a Horizontal Circular Cylinder with Uniform Surface Heat Flux', 10TH INTERNATIONAL CONFERENCE ON MECHANICAL ENGINEERING (ICME 2013), vol. 90, pp. 510-516.View/Download from: Publisher's site
Saleem, M, Hossain, MA, Saha, SC & Gu, YT 2014, 'Heat Transfer Analysis of Viscous Incompressible Fluid by Combined Natural Convection and Radiation in an Open Cavity', MATHEMATICAL PROBLEMS IN ENGINEERING.View/Download from: Publisher's site
Saha, SC, Sauret, E & Gu, YT 2014, 'Magnetic convection heat transfer in an open ended enclosure filled with paramagnetic fluids', Applied Mechanics and Materials, vol. 553, pp. 109-114.View/Download from: Publisher's site
Numerical simulations of thermomagnetic convection of paramagnetic fluids placed in a micro-gravity condition (g 0) and under a uniform vertical gradient magnetic field in an open ended square enclosure with ramp heating temperature condition applied on a vertical wall is investigated in this study. In presence of the strong magnetic gradient field thermal convection of the paramagnetic fluid might take place even in a zero-gravity environment as a direct consequence of temperature differences occurring within the fluid. The thermal boundary layer develops adjacent to the hot wall as soon as the ramp temperature condition is applied on it. There are two scenario that can be observed based on the ramp heating time. The steady state of the thermal boundary layer can be reached before the ramp time is finished or vice versa. If the ramp time is larger than the quasi-steady time then the thermal boundary layer is in a quasi-steady mode with convection balancing conduction after the quasi-steady time. Further increase of the heat input simply accelerates the flow to maintain the proper thermal balance. Finally, the boundary layer becomes completely steady state when the ramp time is finished. Effects of magnetic Rayleigh number, Prandtl number and paramagnetic fluid parameter on the flow pattern and heat transfer are presented. © (2014) Trans Tech Publications, Switzerland.
Abbasi, WS, Shams-Ul-Islam, Saha, SC, Gu, YT & Ying, ZC 2014, 'Effect of Reynolds numbers on flow past four square cylinders in an in-line square configuration for different gap spacings', JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY, vol. 28, no. 2, pp. 539-552.View/Download from: Publisher's site
Islam, M, Karim, MA, Saha, SC, Miller, S & Yarlagadda, PKDV 2014, 'Development of empirical equations for irradiance profile of a standard parabolic trough collector using Monte Carlo ray tracing technique', ENERGY DEVELOPMENT, PTS 1-4, vol. 860-863, pp. 180-+.View/Download from: Publisher's site
Saleem, M, Hossain, MA & Saha, SC 2014, 'Double Diffusive Marangoni Convection Flow of Electrically Conducting Fluid in a Square Cavity With Chemical Reaction', JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME, vol. 136, no. 6.View/Download from: Publisher's site
Sojoudi, A, Mazloomi, A, Saha, SC & Gu, YT 2014, 'Similarity solutions for flow and heat transfer of non-newtonian fluid over a stretching surface', Journal of Applied Mathematics, vol. 2014.View/Download from: Publisher's site
Similarity solutions are carried out for flow of power law non-Newtonian fluid film on unsteady stretching surface subjected to constant heat flux. Free convection heat transfer induces thermal boundary layer within a semi-infinite layer of Boussinesq fluid. The nonlinear coupled partial differential equations (PDE) governing the flow and the boundary conditions are converted to a system of ordinary differential equations (ODE) using two-parameter groups. This technique reduces the number of independent variables by two, and finally the obtained ordinary differential equations are solved numerically for the temperature and velocity using the shooting method. The thermal and velocity boundary layers are studied by the means of Prandtl number and non-Newtonian power index plotted in curves. © 2014 Atta Sojoudi et al.
Siddiqa, S, Hossain, MA & Saha, SC 2014, 'The effect of thermal radiation on the natural convection boundary layer flow over a wavy horizontal surface', INTERNATIONAL JOURNAL OF THERMAL SCIENCES, vol. 84, pp. 143-150.View/Download from: Publisher's site
Saha, SC & Gu, YT 2014, 'Transient air flow and heat transfer in a triangular enclosure with a conducting partition', Applied Mathematical Modelling, vol. 38, no. 15-16, pp. 3879-3887.View/Download from: Publisher's site
Numerical investigation is carried out for natural convection heat transfer in an isosceles triangular enclosure partitioned in the centre by a vertical wall with infinite conductivity. A sudden temperature difference between two zones of the enclosure has been imposed to trigger the natural convection. As a result, heat is transferred between both sides of the enclosure through the conducting vertical wall with natural convection boundary layers forming adjacent to the middle partition and two inclined surfaces. The finite volume based software, Ansys 14.5 (Fluent) is used for the numerical simulations. The numerical results are obtained for different values of aspect ratio, A (0.2, 0.5 and 1.0) and Rayleigh number, Ra (105Ra108) for a fixed Prandtl number, Pr =0.72 of air. It is anticipated from the numerical simulations that the coupled thermal boundary layers development adjacent to the partition undergoes several distinct stages including an initial stage, a transitional stage and a steady stage. Time dependent features of the coupled thermal boundary layers as well as the overall natural convection flow in the partitioned enclosure have been discussed in this study. © 2013 Elsevier Inc.
Xu, F & Saha, SC 2014, 'Transition to an unsteady flow induced by a fin on the sidewall of a differentially heated air-filled square cavity and heat transfer', INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, vol. 71, pp. 236-244.View/Download from: Publisher's site
Sojoudi, A, Saha, SC, Khezerloo, M & Gu, YT 2014, 'Unsteady Natural Convection Within a Porous Enclosure of Sinusoidal Corrugated Side Walls', Transport in Porous Media, vol. 104, no. 3, pp. 537-552.View/Download from: Publisher's site
Numerically investigation of free convection within a porous cavity with differential heating has been performed using modified corrugated side walls. Sinusoidal hot left and cold right walls are assumed to receive sudden differentially heating where top and bottom walls are insulated. Air is considered as working fluid and is quiescent, initially. Numerical experiments reveal 3 distinct stages of developing pattern including initial stage, oscillatory intermediate, and finally steady-state condition. Implicit Finite Volume Method with TDMA solver is used to solve the governing equations. This study has been performed for the Rayleigh numbers ranging from 100 to 10,000. Outcomes have been reported in terms of isotherms, streamline, velocity and temperature plots and average Nusselt number for various Ra, corrugation frequency, and corrugation amplitude (CA). The effects of sudden differential heating and its resultant transient behavior on fluid flow and heat transfer characteristics have been shown for the range of governing parameters. The present results show that the transient phenomena are enormously influenced by the variation of the Rayleigh Number with CA and frequency. © 2014 Springer Science+Business Media Dordrecht.
Saha, SC, Lei, C & Patterson, JC 2014, 'Effect of aspect ratio on natural convection in attics subject to periodic thermal forcing', ANZIAM Journal, vol. 48, pp. C677-C691.
© 2007 Austral. Mathematical Soc. We consider the heat transfer through the attics of buildings under realistic (periodic) thermal forcing. The objective of this study is to investigate numerically the effect of the aspect ratio (height to base ratio) on the heat transfer through the attics. A fixed Grashof number 1:33×106 is considered for three different aspect ratios 0.2, 0.5 and 1.0. The Prandtl number is also fixed at 0.71 for air. The details of the numerical model as well as the ow structures and heat transfer data are presented.
Siddiqa, S, Hossain, MA & Saha, SC 2013, 'Natural Convection Flow with Surface Radiation Along a Vertical Wavy Surface', NUMERICAL HEAT TRANSFER PART A-APPLICATIONS, vol. 64, no. 5, pp. 400-415.View/Download from: Publisher's site
Siddiqa, S, Hossain, MA & Saha, SC 2013, 'Natural convection flow in a strong cross magnetic field with radiation', Journal of Fluids Engineering, Transactions of the ASME, vol. 135, no. 5.View/Download from: Publisher's site
The problem of magnetohydrodynamic natural convection boundary layer flow of an electrically conducting and optically dense gray viscous fluid along a heated vertical plate is analyzed in the presence of strong cross magnetic field with radiative heat transfer. In the analysis radiative heat flux is considered by adopting optically thick radiation limit. Attempt is made to obtain the solutions valid for liquid metals by taking Pra1. Boundary layer equations are transformed in to a convenient dimensionless form by using stream function formulation (SFF) and primitive variable formulation (PVF). Nonsimilar equations obtained from SFF are then simulated by implicit finite difference (Keller-box) method whereas parabolic partial differential equations obtained from PVF are integrated numerically by hiring direct finite difference method over the entire range of local Hartmann parameter, . Further, asymptotic solutions are also obtained for large and small values of local Hartmann parameter . A favorable agreement is found between the results for small, large and all values of . Numerical results are also demonstrated graphically by showing the effect of various physical parameters on shear stress, rate of heat transfer, velocity, and temperature. © 2013 by ASME.
Hasan, MN, Saha, SC & Gu, YT 2013, 'Mixed convection over a horizontal plate with streamwise non-uniform surface temperature distribution', Journal of Heat Transfer, vol. 135, no. 7.View/Download from: Publisher's site
Numerical investigation on mixed convection of a two-dimensional incompressible laminar flow over a horizontal flat plate with streamwise sinusoidal distribution of surface temperature has been performed for different values of Rayleigh number, Reynolds number and frequency of periodic temperature for constant Prandtl number and amplitude of periodic temperature. Finite element method adapted to rectangular nonuniform mesh elements by a nonlinear parametric solution algorithm basis numerical scheme has been employed. The investigating parameters are the Rayleigh number, the Reynolds number and frequency of periodic temperature. The effect of variation of individual investigating parameters on mixed convection flow characteristics has been studied to observe the hydrodynamic and thermal behavior for while keeping the other parameters constant. The fluid considered in this study is air with Prandtl number 0.72. The results are obtained for the Rayleigh number range of 102 to 104, Reynolds number ranging from 1 to 100 and the frequency of periodic temperature from 1 to 5. Isotherms, streamlines, average and local Nusselt numbers are presented to show the effect of the different values of aforementioned investigating parameters on fluid flow and heat transfer. Copyright © 2013 by ASME.
Hossain, MA, Saleem, M, Saha, SC & Nakayama, A 2013, 'Conduction-radiation effect on natural convection flow in fluid-saturated non-Darcy porous medium enclosed by non-isothermal walls', APPLIED MATHEMATICS AND MECHANICS-ENGLISH EDITION, vol. 34, no. 6, pp. 687-702.View/Download from: Publisher's site
Saha, SC 2013, 'Effect of MHD and heat generation on natural convection flow in an open square cavity under microgravity condition', Engineering Computations (Swansea, Wales), vol. 30, no. 1, pp. 5-20.View/Download from: Publisher's site
Purpose - The purpose of this paper is to numerically study thermo-magnetic convection and heat transfer of paramagnetic fluid placed in a micro-gravity condition (g0) and under a uniform vertical gradient magnetic field in an open square cavity with three cold sidewalls. Design/methodology/approach - This magnetic force is proportional to the magnetic susceptibility and the gradient of the square of the magnetic induction. The magnetic susceptibility is inversely proportional to the absolute temperature based on Curie's law. Thermal convection of a paramagnetic fluid can therefore take place even in a zero-gravity environment as a direct consequence of temperature differences occurring within the fluid due to a constant internal heat generation placed within a magnetic field gradient. Findings - Effects of magnetic Rayleigh number, Ra, Prandtl number, Pr, and paramagnetic fluid parameter, m, on the flow pattern and isotherms as well as on the heat absorption are presented graphically. It is found that the heat transfer rate is suppressed in increased of the magnetic Rayleigh number and the paramagnetic fluid parameter for the present investigation. Originality/value - It is possible to control the buoyancy force by using the super conducting magnet. To the best knowledge of the author no literature related to magnetic convection for this configuration is available. © Emerald Group Publishing Limited.
Sauret, E, Saha, SC & Gu, Y 2013, 'Numerical simulations of particle deposition in metal foam heat exchangers', International Journal of Computational Materials Science and Surface Engineering, vol. 2, no. 3-4.View/Download from: Publisher's site
© Imperial College Press. Australia is a high-potential country for geothermal power with reserves currently estimated in the tens of millions of petajoules, enough to power the nation for at least 1000 years at current usage. However, these resources are mainly located in isolated arid regions where water is scarce. Therefore, wet cooling systems for geothermal plants in Australia are the least attractive solution and thus air-cooled heat exchangers are preferred. In order to increase the efficiency of such heat exchangers, metal foams have been used. One issue raised by this solution is the fouling caused by dust deposition. In this case, the heat transfer characteristics of the metal foam heat exchanger can dramatically deteriorate. Exploring the particle deposition property in the metal foam exchanger becomes crucial. This paper is a numerical investigation aimed to address this issue. Two-dimensional (2D) numerical simulations of a standard one-row tube bundle wrapped with metal foam in cross-flow are performed and highlight preferential particle deposition areas.
Sojoudi, A, Saha, SC, Gu, YT & Hossain, MA 2013, 'Steady natural convection of non-newtonian power-law fluid in a trapezoidal enclosure', Advances in Mechanical Engineering, vol. 2013.View/Download from: Publisher's site
Numerical investigation of free convection heat transfer in a differentially heated trapezoidal cavity filled with non-Newtonian Power-law fluid has been performed in this study. The left inclined surface is uniformly heated whereas the right inclined surface is maintained as uniformly cooled. The top and bottom surfaces are kept adiabatic with initially quiescent fluid inside the enclosure. Finite-volume-based commercial software FLUENT 14.5 is used to solve the governing equations. Dependency of various flow parameters of fluid flow and heat transfer is analyzed including Rayleigh number (Ra) ranging from 105 to 107, Prandtl number (Pr) from 100 to 10,000, and power-law index (n) from 0.6 to 1.4. Outcomes have been reported in terms of isotherms, streamlines, and local Nusselt number for various Ra, Pr, n, and inclined angles. Grid sensitivity analysis is performed and numerically obtained results have been compared with those results available in the literature and were in good agreement. © 2013 Atta Sojoudi et al.
Sojoudi, A & C. Saha, S 2013, 'Shear Thinning and Shear Thickening Non- Newtonian Confined Fluid Flow over Rotating Cylinder', American Journal of Fluid Dynamics, vol. 2, no. 6, pp. 117-121.View/Download from: Publisher's site
Molla, MM, Saha, SC & Khan, MAI 2012, 'MHD natural convection flow from an isothermal horizontal circular cylinder under consideration of temperature dependent viscosity', ENGINEERING COMPUTATIONS, vol. 29, no. 7-8, pp. 875-887.View/Download from: Publisher's site
Saha, SC & Khan, MMK 2012, 'An improved boundary layer scaling with ramp heating on a sloping plate', International Journal of Heat and Mass Transfer, vol. 55, no. 9-10, pp. 2268-2284.View/Download from: Publisher's site
A scaling analysis for the natural convection boundary layer adjacent to an inclined semi-infinite plate subject to a non-instantaneous heating in the form of an imposed wall temperature which increases linearly up to a prescribed steady value over a prescribed time is reported. The development of the boundary layer flow from start-up to a steady-state has been described based on scaling analyses and verified by numerical simulations. The analysis reveals that, if the period of temperature growth on the wall is sufficiently long, the boundary layer reaches a quasi-steady mode before the growth of the temperature is completed. In this mode the thermal boundary layer at first grows in thickness and then contracts with increasing time. However, if the imposed wall temperature growth period is sufficiently short, the boundary layer develops differently, but after the wall temperature growth is completed, the boundary layer develops as though the startup had been instantaneous. The steady state values of the boundary layer for both cases are ultimately the same. © 2012 Elsevier Ltd. All rights reserved.
Hasan, MN, Saha, S & Saha, SC 2012, 'Effects of corrugation frequency and aspect ratio on natural convection within an enclosure having sinusoidal corrugation over a heated top surface', INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER, vol. 39, no. 3, pp. 368-377.View/Download from: Publisher's site
Saha, SC, Brown, RJ & Gu, YT 2012, 'Scaling for the Prandtl number of the natural convection boundary layer of an inclined flat plate under uniform surface heat flux', INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, vol. 55, no. 9-10, pp. 2394-2401.View/Download from: Publisher's site
Saleem, M, Hossain, MA & Saha, SC 2012, 'Mixed Convection Flow of Micropolar Fluid in an Open Ended Arc-Shape Cavity', JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME, vol. 134, no. 9.View/Download from: Publisher's site
Hasan, MN, Saha, SC & Gu, YT 2012, 'Unsteady natural convection within a differentially heated enclosure of sinusoidal corrugated side walls', INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, vol. 55, no. 21-22, pp. 5696-5708.View/Download from: Publisher's site
Saha, SC, Brown, RJ & Gu, YT 2012, 'Prandtl number scaling of the unsteady natural convection boundary layer adjacent to a vertical flat plate for Pr > 1 subject to ramp surface heat flux', INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, vol. 55, no. 23-24, pp. 7046-7055.View/Download from: Publisher's site
Molla, MM, Saha, SC & Hossain, MA 2012, 'The Effect of Temperature Dependent Viscosity on MHD Natural Convection Flow from an Isothermal Sphere', JOURNAL OF APPLIED FLUID MECHANICS, vol. 5, no. 2, pp. 25-31.
Saha, SC, Gu, Y, Molla, MM, Siddiqa, S & Hossain, MA 2012, 'Natural convection from a vertical plate embedded in a stratified medium with uniform heat source', DESALINATION AND WATER TREATMENT, vol. 44, no. 1-3, pp. 7-14.View/Download from: Publisher's site
Siddiqa, S, Hossain, MA & Saha, SC 2012, 'Double Diffusive Magneto-Convection Fluid Flow in a Strong Cross Magnetic Field With Uniform Surface Heat and Mass Flux', JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME, vol. 134, no. 11.View/Download from: Publisher's site
Molla, MM, Saha, SC, Khan, MAI & Hossain, MA 2011, 'Radiation effects on natural convection laminar flow from a horizontal circular cylinder', DESALINATION AND WATER TREATMENT, vol. 30, no. 1-3, pp. 89-97.View/Download from: Publisher's site
Saha, SC, Xu, F & Molla, MM 2011, 'Scaling Analysis of the Unsteady Natural Convection Boundary Layer Adjacent to an Inclined Plate for Pr > 1 Following Instantaneous Heating', JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME, vol. 133, no. 11.View/Download from: Publisher's site
Saha, SC, Patterson, JC & Lei, C 2011, 'Scaling of natural convection of an inclined flat plate: Sudden cooling condition', Journal of Heat Transfer, vol. 133, no. 4.View/Download from: Publisher's site
The natural convection boundary layer adjacent to an inclined plate subject to sudden cooling boundary condition has been studied. It is found that the cold boundary layer adjacent to the plate is potentially unstable to Rayleigh-Bénard instability if the Rayleigh number exceeds a certain critical value. A scaling relation for the onset of instability of the boundary layer is achieved. The scaling relations have been developed by equating important terms of the governing equations based on the development of the boundary layer with time. The flow adjacent to the plate can be classified broadly into a conductive, a stable convective, or an unstable convective regime determined by the Rayleigh number. Proper scales have been established to quantify the flow properties in each of these flow regimes. An appropriate identification of the time when the instability may set in is discussed. A numerical verification of the time for the onset of instability is also presented in this study. Different flow regimes based on the stability of the boundary layer have been discussed with numerical results. © 2011 American Society of Mechanical Engineers.
Saha, SC & Gu, YT 2011, 'Free convection in a triangular enclosure with fluid-saturated porous medium and internal heat generation', ANZIAM Journal, vol. 53, no. SUPPL.
Unsteady natural convection inside a triangular cavity is studied. The cavity is filled with a saturated porous medium has a non-isothermal left inclined wall while the bottom surface is isothermally heated and the right inclined surface is isothermally cooled. Internal heat generation is also considered, which is dependent on the fluid temperature. The governing equations are solved numerically by the finite volume method. The Prandtl number of the fluid is chosen to be 0.7 (air) whereas the aspect ratio and the Rayleigh number are 0.5 and 105, respectively. The effect of heat generation on the fluid flow and heat transfer is presented in terms of streamlines and isotherms. The rate of heat transfer through the three surfaces of the enclosure is also presented. © Austral. Mathematical Soc. 2012.
Saha, SC & Gu, YT 2011, 'Natural convection in a triangular enclosure due to non-uniform cooling on top', ANZIAM Journal, vol. 53, no. SUPPL.
Natural convection in a triangular enclosure subject to non-uniform cooling at the inclined surfaces and uniform heating at the base is investigated numerically. The numerical simulations of the unsteady flows over a range of Rayleigh numbers and aspect ratios are carried out using the Finite Volume Method. Since the upper surface is cooled and the bottom surface is heated, the air flow in the enclosure is potentially unstable to Rayleigh-Benard instability. Based on the numerical results, the transient flow development in the enclosure is classified into three distinct stages: an early stage, a transitional stage, and a steady stage. In addition, the flow inside the enclosure strongly depends on the governing parameters; Rayleigh number and aspect ratio. The asymmetric behaviour of the flow about the geometric centre line is discussed in detailed. The heat transfer through the roof and the ceiling as a form of Nusselt number is also reported. © Austral. Mathematical Soc. 2012.
Saha, SC & Gu, YT 2011, 'Prandtl number scaling of natural convection of the flow on a heated inclined at plate', ANZIAM Journal, vol. 53, no. SUPPL.
A new scaling analysis has been performed for the unsteady natural convection boundary layer under a downward facing inclined plate with uniform heat flux. The development of the thermal or viscous boundary layers is classified into three distinct stages including an early stage, a transitional stage and a steady stage, which is clearly identified in the analytical as well as in numerical results. Earlier scaling shows that the existing scaling laws of the boundary layer thickness, velocity and steady state time scales for the natural convection flow on a heated plate of uniform heat flux provide a very poor prediction of the Prandtl number dependency. However, those scalings performed very well with Rayleigh number and aspect ratio dependency. In this study, a modified Prandtl number scaling is developed using a triple-layer integral approach for Prandtl number larger than unity. In comparison to the direct numerical simulations, the new scaling performs considerably better than the previous scaling. © Austral. Mathematical Soc. 2012.
Molla, MM, Saha, SC & Hossain, MA 2011, 'Radiation effect on free convection laminar flow along a vertical flat plate with streamwise sinusoidal surface temperature', MATHEMATICAL AND COMPUTER MODELLING, vol. 53, no. 5-6, pp. 1310-1319.View/Download from: Publisher's site
Saha, SC, Patterson, JC & Lei, C 2010, 'Natural convection boundary-layer adjacent to an inclined flat plate subject to sudden and ramp heating', INTERNATIONAL JOURNAL OF THERMAL SCIENCES, vol. 49, no. 9, pp. 1600-1612.View/Download from: Publisher's site
Saha, SC, Patterson, JC & Lei, C 2010, 'Natural convection and heat transfer in attics subject to periodic thermal forcing', INTERNATIONAL JOURNAL OF THERMAL SCIENCES, vol. 49, no. 10, pp. 1899-1910.View/Download from: Publisher's site
Saha, SC, Patterson, JC & Lei, C 2010, 'Scaling of natural convection of an inclined flat plate: Ramp cooling condition', International Journal of Heat and Mass Transfer, vol. 53, no. 23-24, pp. 5156-5166.View/Download from: Publisher's site
A scaling analysis is performed for the transient boundary layer established adjacent to an inclined flat plate following a ramp cooling boundary condition. The imposed wall temperature decreases linearly up to a specific value over a specific time. It is revealed that if the ramp time is sufficiently large then the boundary layer reaches quasi-steady mode before the growth of the temperature is finished. However, if the ramp time is shorter then the steady state of the boundary layer may be reached after the growth of the temperature is completed. In this case, the ultimate steady state is the same as if the start up had been instantaneous. Note that the cold boundary layer adjacent to the plate is potentially unstable to Rayleigh-Bénard instability if the Rayleigh number exceeds a certain critical value for this cooling case. The onset of instability may set in at different stages of the boundary layer development. A proper identification of the time when the instability may set in is discussed. A numerical verification of the time for the onset of instability is presented in this study. Different flow regimes based on the stability of the boundary layer have also been discussed with numerical results. © 2010 Elsevier Ltd. All rights reserved.
Saha, SC, Patterson, JC & Lei, C 2010, 'Natural convection in attics subject to instantaneous and ramp cooling boundary conditions', ENERGY AND BUILDINGS, vol. 42, no. 8, pp. 1192-1204.View/Download from: Publisher's site
Saha, SC, Patterson, JC & Lei, C 2010, 'Natural convection in attic-shaped spaces subject to sudden and ramp heating boundary conditions', HEAT AND MASS TRANSFER, vol. 46, no. 6, pp. 621-638.View/Download from: Publisher's site
Hossain, MA, Saha, SC & Gorla, RSR 2005, 'Viscous dissipation effects on natural convection from a vertical plate with uniform surface heat flux placed in a thermally stratified media', International Journal of Fluid Mechanics Research, vol. 32, no. 3, pp. 269-280.View/Download from: Publisher's site
In the present study we investigate the effect of viscous dissipation on natural convection from a vertical plate placed in a thermally stratified environment. The reduced equations are integrated by employing the implicit finite difference scheme of Keller box method and obtained the effect of heat due to viscous dissipation on the local skin friction and local Nusselt number at various stratification levels, for fluids having Prandtl numbers of 10, 50, and 100. Solutions are also obtained using the perturbation technique for small values of viscous dissipation parameters and compared to the finite difference solutions for 0 1. Effect of viscous dissipation and temperature stratification are also shown on the velocity and temperature distributions in the boundary layer region. © 2005 Begell House, Inc.
Barns, S, Sauret, E, Saha, S, Flower, R & Gu, YT, 'Two-Layer Red Blood Cell Membrane Model Using the Discrete Element Method', Applied Mechanics and Materials, vol. 846, pp. 270-275.View/Download from: Publisher's site
The red blood cell (RBC) membrane consists of a lipid bilayer and spectrin-based cytoskeleton, which enclose haemoglobin-rich fluid. Numerical models of RBCs typically integrate the two membrane components into a single layer, preventing investigation of bilayer-cytoskeleton interaction. To address this constraint, a new RBC model which considers the bilayer and cytoskeleton separately is developed using the discrete element method (DEM). This is completed in 2D as a proof-of-concept, with an extension to 3D planned in the future. Resting RBC morphology predicted by the two-layer model is compared to an equivalent and well-established composite (one-layer) model with excellent agreement for critical cell dimensions. A parametric study is performed where area reduction ratio and spring constants are varied. It is found that predicted resting geometry is relatively insensitive to changes in spring stiffness, but a shape variation is observed for reduction ratio changes as expected.
Khanal, S & Bhatta, BP, 'Evaluating Efficiency of Personnel in Nepalese Commercial Banks: A Data Envelopment Analysis', SSRN Electronic Journal.View/Download from: Publisher's site
© Springer Nature Singapore Pte Ltd. 2018. To reduce the natural convection heat loss from attic-shaped spaces, many researchers used convection suppression devices in the past. In this chapter, a single baffle is used under the top tip to investigate numerically the natural convection heat loss in an attic-shaped enclosure, which is a cost-effective approach. The case considered in this chapter is one inclined wall of the enclosure which is uniformly heated while the other inclined wall uniformly cooled with adiabatic bottom wall. The finite volume method has been used to discretize the governing equations, with the QUICK scheme approximating the advection term. The diffusion terms are discretized using central differencing with second-order accuracy. A wide range of governing parameters is studied (Rayleigh number, aspect ratio, baffle length, etc.). It is observed that the heat transfer due to natural convection in the enclosure reduces when the baffle length is increased. Effects of other parameters on heat transfer and flow field are described in this study.
Farhad Ismail, M & Saha, SC 2018, 'Enhancement of confined air jet impingement heat transfer using perforated pin-fin heat sinks' in Green Energy and Technology, pp. 231-243.View/Download from: Publisher's site
© Springer Nature Singapore Pte Ltd. 2018. The development of semiconductor fabrication process and electronic packaging technology causes the size and weight of electronic components to decrease consistently. Along with the increasing operating power, the heat generation rate of the electronic products apparently gets higher. For the sustainable future, we must limit using natural resources and also reduce the greenhouse gas emission. Efficient removal of heat from the electronic products in a limited space becomes a major task in electronics cooling. Air impingement cooling with a heat sink is an attractive option for electronic cooling, because it is inexpensive, robust, and localized. Rapid heat transfer from heated surfaces and reducing material weight is also becoming a major task for the design of heat exchanger equipment for electronic cooling. Rectangular plate fins as extended surfaces are good heat transfer equipment which are widely used for various industrial applications. Heat transfer rate can be improved by introducing perforations, porosity, or slots. Moreover, due to restrictions in setup space and economic reasons, heat transfer equipment has been required to be much more compact in size and lighter in weight. Studies on three-dimensional plate and pin-fin heat sinks are extensive. But no focus has been yet given on air jet impingement heat transfer with perforated pin-fin heat sink. Thermal-fluid characteristics of solid and perforated pin-fin heat sinks cooled by confined air jet impingement are investigated numerically in this study. The SST k- turbulence model is used to predict the turbulence flow parameters. The numerical model is verified with previously published experimental data. Flow and heat transfer characteristics are presented for the impinging Reynolds number, Re = 500025000 having constant impingement distance (Y/D = 8), fin width (W/L = 0.1), and height (H/L = 0.5). The main objective of this study is to examine the effects ...
Islam, M, Saha, SC, Karim, MA & Yarlagadda, PKDV 2018, 'A method of three-dimensional thermo-fluid simulation of the receiver of a standard parabolic trough collector' in Green Energy and Technology, pp. 203-230.View/Download from: Publisher's site
© Springer Nature Singapore Pte Ltd. 2018. A parabolic trough collector (PTC) is the most proven concentrating collector system for indirect steam generation in solar thermal power plants. The receiver of the collector is fabricated enveloping a metal absorber tube using an evacuated glass tube. Depending on the level of evacuation, the glass envelope reduces the convection heat loss from the tube almost to zero. However, sometimes the envelopes are broken, damaged or removed that causes potential convection loss from an open-to-air receiver tube. On the other hand, the solar irradiance profile around the receiver tube is likely to be highly nonuniform. In order to study the heat transfer mechanism of an exposed receiver tube of a standard PTC under the actual optical and environmental conditions, a 3-dimensional Computational Conjugate Heat Transfer (CCHT) model of the receiver tube was developed. The CCHT model was developed applying finite volume technique of computational fluid dynamics integrating with a verified Monte Carlo ray tracing optical model. The CCHT model was verified extensively, and different heat loss models were developed to investigate the heat loss characteristics. The convection heat loss from the outer surface of the receiver tube was observed very high as it was exposed to a high-temperature gradient with its surroundings. Therefore, it is obvious that the receiver tube should be enveloped and evacuated properly. A well-managed and efficiently operated PTC solar energy field could be the best candidate for sustainable energy management for a sustainable future.
Das, P, Khan, MMK, Saha, SC & Rasul, MG 2015, 'Numerical Study of Flow Through a Reducer for Scale Growth Suppression' in Thermofluid Modeling for Energy Efficiency Applications, pp. 119-148.View/Download from: Publisher's site
© 2016 Elsevier Inc. All rights reserved. Scale formation in alumina refineries is a common phenomenon and it occurs where supersaturated solutions are in contact with solid surfaces. It often leads to serious on-going technical problems and is a major cause of production loss due to equipment downtime required for descaling and cleaning operations.The scale formation mechanism in Bayer process equipment is complex and is not yet fully understood. Numerous researchers indicate that scale growth is strongly affected by fluid velocity while also being influenced by a number of other factors such as the quality of bauxite ore, rheological properties of fluid, turbulence and inertia of suspended particles, and adhesive property of particles. It is common knowledge that, if the particles approach the wall at right angles, the chance to cross the laminar sub-layer to accumulate scale on the solid surface increases. The components (stream-wise (. u'x) and cross-stream (. u'r)) of the fluctuating velocity play a critical role in whether the potential for scale formation is increased or suppressed.In this chapter, a numerical study using the Finite Volume Method to analyze the fluid dynamics behavior of water as it flows through a concentric reducer used in the Bayer plant is presented. The simulation results show a significant variation of the stream-wise (. u'x) and cross-stream (. u'r) components of the fluctuating velocity as flow passes through the concentric reducer. In the reducer, the cross-stream (. u'r) component is greater than that at the walls of the straight pipes connected to the reducer. The variation of the cross-stream component of the fluctuating velocity is believed to be accountable for the increase in scale deposition at the reducer section.
Ismail, MF, Saha, SC & Rashid Sarkar, MA 2015, 'Effects of Perforation Geometry on the Heat Transfer Performance of Extended Surfaces' in Thermofluid Modeling for Energy Efficiency Applications, pp. 103-117.View/Download from: Publisher's site
© 2016 Elsevier Inc. All rights reserved. In this study heat transfer performances of extended surfaces (fins) having square, circular, hexagonal, and triangular lateral perforations are studied numerically. Simulations are carried out for Reynolds numbers ranging from 100 to 400 based on the fin thickness. Numerical results are first validated with previously published results and a good agreement is observed. For each type, Nusselt number, average drag, and heat removal rate of perforated fins are determined and compared. Results show that perforation geometry has significant effects on the thermal and fluid dynamic performance of the extended surfaces. All types of perforated fins show better heat transfer performance enhancement than the regular solid fins.
Saha, SC, Gu, YT & Khan, MMK 2015, 'Natural Convection Heat Transfer in the Partitioned Attic Space' in Thermofluid Modeling for Energy Efficiency Applications, pp. 59-72.View/Download from: Publisher's site
© 2016 Elsevier Inc. All rights reserved. Heat transfer and air flow through an attic space into or out of buildings is a key issue for attic-shaped houses in different seasons. One of the main objectives for designers and builders is to provide thermal comfort for dwellers. In the present energy-conscious society, it is also a requirement for houses to be energy-efficient, that is, the energy usage for heating or cooling houses must be reduced. Relevant to these objectives, research into heat transfer in attics has been conducted for more than two decades. Numerical simulation is carried out for flow behavior of natural convection in an isosceles triangular enclosure partitioned in the center by a vertical wall with an infinite conductivity. A sudden temperature difference between two zones of the enclosure has been imposed to trigger the natural convection. As a result, heat is transferred between both sides of the cavity through the conducting vertical wall with natural convection boundary layers forming on the middle partition and two inclined surfaces. The Finite Volume-based software Fluent is used for the simulations. The numerical results are obtained for different values of height-base ratio (. 0.2,0.5, and 1.0) with fixed values of Rayleigh number, 108 and Prandtl number, 0.72. It is anticipated from the numerical simulations that the coupled thermal boundary layers development adjacent to the partition undergoes several distinct stages including an initial stage, a transitional stage, and a steady stage. Time-dependent features of the coupled thermal boundary layers, as well as the overall natural convection flow in the partitioned enclosure, have been discussed and compared with the nonpartitioned enclosure. It is found that heat transfer is reduced significantly in the presence of a vertical partition which is placed in the geometrical center line.
Mahabaleswar, US & Saha, SC 2013, 'Analytical solution of a walters' liquid b flow over a linear stretching sheet in a porous medium' in Focus on Porous Media Research, pp. 121-130.
© 2013 by Nova Science Publishers, Inc. All rights reserved. This Chapter represents the analytical solution of a two-dimensional linear stretching sheet problem involving a non-Newtonian liquid and suction by (a) invoking the boundary layer approximation and (b) using this result to solve the stretching sheet problem without using boundary layer approximation. The basic boundary layer equations for momentum, which are non-linear partial differential equations, are converted into non-linear ordinary differential equations by means of similarity transformation. The results reveal a new analytical procedure for solving the boundary layer equations arising in a linear stretching sheet problem involving a non-Newtonian liquid (Walters' liquid B). The present study sheds light on the analytical solution of a class of boundary layer equations arising in the stretching sheet problem.
Siddiki, MNAA, Molla, MM, Thohura, S & Saha, SC 2018, 'Lattice Boltzmann simulation of Non-Newtonian power-law fluid flows in a bifurcated channel', AIP Conference Proceedings.View/Download from: Publisher's site
© 2018 Author(s). The present paper aims to study of non-Newtonian fluid flow behaviors in a two-dimensional bifurcated channel using lattice-Boltzmann method (LBM). In this LBM, well known D2Q9 model, and the single-relaxation-time (SRT) called the Lattice-BGK (Bhatnagar-Gross-Krook) approach has been adopted. In a bifurcated channel, the flow patterns are analogous to blood flows in branched arteries. Firstly, the code is validated by comparing the available published results for the Newtonian fluid flows in a channel with T-junction. The numerical results are simulated for the Reynolds number Re = 300, power-law index n = 0.5, 1.0 and 1.5, and the outlet flow rate ratio . The effects of this relevant parameter on the streamlines, velocity distribution, recirculation zones as well as wall shear stress will be discussed to analyze the hemodynamic of blood flows near arterial bifurcations.
Islam, MS, Saha, SC, Sauret, E, Gu, YT & Molla, MM 2016, 'Numerical investigation of diesel exhaust particle transport and deposition in the CT-scan based lung airway', AIP Conference Proceedings, BSME INTERNATIONAL CONFERENCE ON THERMAL ENGINEERING, Dhaka, Bangladesh.View/Download from: Publisher's site
© 2017 Author(s). Diesel exhaust particulates matter (DEPM) is a compound mixture of gasses and fine particles that contain more than 40 toxic air pollutants including benzene, formaldehyde, and nitrogen oxides. Exposure of DEPM to human lung airway during respiratory inhalation causes severe health hazards like diverse pulmonary diseases. This paper studies the DEPM transport and deposition in upper three generations of the realistic lung airways. A 3-D digital airway bifurcation model is constructed from the computerized tomography (CT) scan data of a healthy adult man. The Euler-Lagrange approach is used to solve the continuum and disperse phases of the calculation. Local averaged Navier-Stokes equations are solved to calculate the transport of the continuum phase. Lagrangian based Discrete Phase Model (DPM) is used to investigate the particle transport and deposition in the current anatomical model. The effects of size specific monodispersed particles on deposition are extensively investigated during different breathing pattern. The numerical results illustrate that particle diameter and breathing pattern have a substantial impact on particles transport and deposition in the tracheobronchial airways. The present realistic bifurcation model also depicts a new deposition hot spot which could advance the understanding of the therapeutic drug delivery system to the specific position of the respiratory airways.
Siddiki, MNAA, Molla, MM & Saha, SC 2016, 'Natural convection flow in porous enclosure with localized heating from below with heat flux', AIP Conference Proceedings.View/Download from: Publisher's site
© 2016 Author(s). Unsteady natural convection flow in a two dimensional fluid saturated porous enclosure with localized heating from below with heat flux, symmetrical cooling from the sides and the insulated top wall has been investigated numerically. The governing equations are the Darcy's law for the porous media and the energy equation for the temperature field has been considered. The non-dimensional Darcy's law in terms of the stream function is solved by finite difference method using the successive over-relaxation (SOR) scheme and the energy equation is solved by Alternative Direction Alternative (ADI) scheme. The uniform heat flux source is located centrally at the bottom wall. The numerical results are presented in terms of the streamlines and isotherms, as well as the local and average rate of heat transfer for the wide range of the Darcy's Rayleigh number and the length of the heat flux source at the bottom wall.
Bhowmick, S, Xu, F & Saha, SC 2015, 'Transient Natural Convection in a Valley Shaped Triangular Cavity Initially Filled with Stratified Water', PROCEEDINGS OF THE 11TH INTERNATIONAL CONFERENCE ON MECHANICAL ENGINEERING (ICME 2015), 11th International Conference on Mechanical Engineering (ICME), AMER INST PHYSICS, Bangladesh Univ Engn & Technol, Dhaka, BANGLADESH.View/Download from: Publisher's site
Gallage, HNP, Saha, SC & Gu, YT 2014, 'Deformation of a three-dimensional red blood cell in a stenosed micro-capillary', 8th Australasian Congress on Applied Mechanics, ACAM 2014, as Part of Engineers Australia Convention 2014, pp. 273-279.
Red blood cells (RBCs) exhibit different types of motions and deformations when the blood flows through capillaries. Interestingly, due to the complex three-dimensional structure of the RBC membrane, RBCs show three-dimensional motions and deformations in the blood flow. These motions and deformations of the RBCs highly depend on the stiffness of the RBC membrane and on the geometrical parameters of the capillary through which blood flows. However, capillaries always do not have uniform cross sections and some capillaries have stenosed segments, where cross sectional area suddenly reduces. Further, some diseases can alter the stiffness of the RBC membrane drastically. In this study, the deformation behaviour of a single three-dimensional RBC is examined, when it moves through a stenosed capillary. A three-dimensional spring network is used to model the RBC membrane. The RBC's inside and outside fluids are discretized into a finite number of mass points and treated by smoothed particle hydrodynamics (SPH) method. The capillary is considered as a rigid tube with a stenosed section. The deformation index, mean velocity and total energy of the RBC are analysed when it flows through the stenosed capillary. Further, motion and deformation of the RBCs with different membrane stiffness (KB) are compared when they flow through the stenosed segment of the capillary. The simulation results demonstrate the RBCs are subjected to a larger deformation when they move through the stenosed part of the capillary and the RBCs with lower KB values easily pass through the stenosed segment of the capillary. Further, RBCs having higher KB values have a lower mean velocity and it leads to slow down the overall blood flow rate.
Sauret, E, Hooman, K & Saha, SC 2014, 'CFD simulations of flow and heat transfer through the porous interface of a metal foam heat exchanger', American Society of Mechanical Engineers, Power Division (Publication) POWER.View/Download from: Publisher's site
Copyright © 2014 by ASME. This paper offers numerical modelling of a waste heat recovery system. A thin layer of metal foam is attached to a cold plate to absorb heat from hot gases leaving the system. The heat transferred from the exhaust gas is then transferred to a cold liquid flowing in a secondary loop. Two different foam PPI (Pores Per Inch) values are examined over a range of fluid velocities. Numerical results are then compared to both experimental data and theoretical results available in the literature. Challenges in getting the simulation results to match those of the experiments are addressed and discussed in detail. In particular, interface boundary conditions specified between a porous layer and a fluid layer are investigated. While physically one expects much lower fluid velocity in the pores compared to that of free flow, capturing this sharp gradient at the interface can add to the difficulties of numerical simulation. The existing models in the literature are modified by considering the pressure gradient inside and outside the foam. Comparisons against the numerical modelling are presented. Finally, based on experimentally-validated numerical results, thermo-hydraulic performance of foam heat exchangers as waste heat recovery units is discussed with the main goal of reducing the excess pressure drop and maximising the amount of heat that can be recovered from the hot gas stream.
Saha, SC, Rannie, M, Sauret, E & Gu, YT 2014, 'Numerical modelling for improved underground-mine ventilation systems', 8th Australasian Congress on Applied Mechanics, ACAM 2014, as Part of Engineers Australia Convention 2014, pp. 747-754.
Diesel engine is commonly used in the underground mining heavy vehicle. However, particle emissions from combustion engine have been declared to be a serious concern for the human health as well as the environment. Diesel engines are one of the most important sources of particulate and NOx emissions which consumes significant amount of oxygen which is dangerous for the mine workers as they will receive insufficient oxygen supply. Therefore, we need to design a proper ventilation system so that adequate oxygen can be supplied and keep the hazardous gas or ultrafine particles concentration as an allowable level in the mining tunnels. The main objective of this study is to find a high concentration area in the mining tunnel and propose and examine various ventilation strategies to control the concentration level to ensure health and safety, work efficiency and cost related to energy consumption. The well-established computational fluid dynamics (CFD) approach has been carried out to investigate the airflow, particle tracing and the position of the ventilation system. A three dimensional unsteady model is developed in this study for an underground mine tunnel with heavy vehicle is in operation. The commercial CFD software, ANSYS 15 (CFX) has been used for the numerical simulation. An Eulerian-Lagrangian approach is used to respectively model the main flow and particules' trajectories.
Saha, S, Hossen, S, Hasib, MH & Saha, SC 2014, 'Onset of transition in mixed convection of a lid-driven trapezoidal enclosure filled with water-Al2O3nanofluid', Proceedings of the 19th Australasian Fluid Mechanics Conference, AFMC 2014.
A numerical study is carried out to investigate the transition from laminar to chaos in mixed convection heat transfer inside a lid-driven trapezoidal enclosure. In this study, the top wall is considered as isothermal cold surface, which is moving in its own plane at a constant speed, and a constant high temperature is provided at the bottom surface. The enclosure is assumed to be filled with water-Al2O3nanofluid. The governing Navier-Stokes and thermal energy equations are expressed in non-dimensional forms and are solved using Galerkin finite element method. Attention is paid in the present study on the pure mixed convection regime at Richandson number, Ri = 1. The numerical simulations are carried out over a wide range of Reynolds (0.1 Re 103) and Grashof (0.01 Gr 106) numbers. Effects of the presence of nanofluid on the characteristics of mixed convection heat transfer are also explored. The average Nusselt numbers of the heated wall are computed to demonstrate the influence of flow parameter variations on heat transfer. The corresponding change of flow and thermal fields is visualized from the streamline and the isotherm contour plots.
Saha, SC & Gu, YT 2014, 'Natural convection heat transfer in a baffled triangular enclosure', Proceedings of the 19th Australasian Fluid Mechanics Conference, AFMC 2014.
To reduce the natural convection heat loss from enclosures many researchers used convection suppression devices in the past. In this study a single baffle is used under the top tip to investigate numerically the natural convection heat loss in an attic shaped enclosure which is a cost effective approach. The case considered here is one inclined wall of the enclosure is uniformly heated while the other inclined wall is uniformly cooled with adiabatic bottom wall. The finite volume method has been used to discretize the governing equations, with the QUICK scheme approximating the advection term. The diffusion terms are discretized using central-differencing with second order accuracy. A wide range of governing parameters are studied (Rayleigh number, aspect ratio, baffle length etc.). It is observed that the heat transfer due to natural convection in the enclosure reduces when the baffle length is increased. Effects of other parameters on heat transfer and flow field are described in this study.
Saha, SC & Gu, YT 2012, 'Thermo-magnetic convection of paramagnetic fluids with non-instantaneous heating', Proceedings of the 18th Australasian Fluid Mechanics Conference, AFMC 2012.
The unsteady boundary-layer development for thermo-magnetic convection of paramagnetic fluids inside a square cavity has been considered in this study. The cavity is placed in a microgravity condition (no gravitation acceleration) and under a uniform magnetic field which acts vertically. A ramp temperature boundary condition is applied on left vertical side wall of the cavity where the temperature initially increases with time up to some specific time and maintain constant thereafter. A distinct magnetic convection boundary layer is developed adjacent to the left vertical wall due to the effect of the magnetic body force generated on the paramagnetic fluid. An improved scaling analysis has been performed using triple-layer integral method and verified by numerical simulations. The Prandtl number has been chosen greater than unity varied over 5-100. Moreover, the effect of various values of the magnetic parameter and magnetic Rayleigh number on the fluid flow and heat transfer has been shown.
Sojoudi, A, Vakilimoghaddam, F, Neishabouri, R & Saha, SC 2012, 'On the oscillatory behavior of transient rayleigh benard convection of air for 2D channel flow at moderate rayleigh numbers', Lecture Notes in Engineering and Computer Science, pp. 1874-1878.
© 2012 Newswood Limited. All rights reserved. Unsteady numerical simulation of Rayleigh Benard convection heat transfer from a 2D channel is performed. The oscillatory behavior is attributed to recirculation of ascending and descending flows towards the core of the channel producing organized rolled motions. Variation of the parameters such as Reynolds number, channel outlet flow area and inclination of the channel are considered. Increasing Reynolds number (for a fixed Rayleigh number), delays the generation of vortices. The reduction in the outflow area leads to the later and the less vortex generation. As the time progresses, more vortices are generated, but the reinforced mean velocity does not let the eddies to enter the core of the channel. Therefore, they attach to the wall and reduce the heat transfer area. The inclination of the channel (both positive and negative) induces the generated vortices to get closer to each other and make an enlarged vortex.
Saha, SC, Lei, C & Patterson, JC 2007, 'On the natural convection boundary layer adjacent to an inclined flat plate subject to ramp heating', Proceedings of the 16th Australasian Fluid Mechanics Conference, 16AFMC, pp. 121-124.
An investigation of the natural convection boundary layer adjacent to an inclined semi-infinite plate subject to a temperature boundary condition which follows a ramp function up until some specified time and then remains constant is reported. The development of the flow from start-up to a steadystate has been described based on scaling analyses and verified by numerical simulations. Attention in this study has been given to fluids having a Prandtl number Pr less than unity. The boundary layer flow depends on the comparison of the time at which the ramp heating is completed and the time at which the boundary layer completes its growth. If the ramp time is long compared with the steady state time, the layer reaches a quasi steady mode in which the growth of the layer is governed solely by the thermal balance between convection and conduction. On the other hand, if the ramp is completed before the layer becomes steady; the subsequent growth is governed by the balance between buoyancy and inertia, as for the case of instantaneous heating.
Saha, SC, Lei, C & Patterson, JC 2007, 'Scaling analysis of the thermal boundary layer adjacent to an abruptly heated inclined flat plate', Proceedings of the 16th Australasian Fluid Mechanics Conference, 16AFMC, pp. 117-120.
The natural convection thermal boundary layer adjacent to an abruptly heated inclined flat plate is investigated through a scaling analysis and verified by numerical simulations. In general, the development of the thermal flow can be characterized by three distinct stages, i.e. a start-up stage, a transitional stage and a steady state stage. Major scales including the flow velocity, flow development time, and the thermal and viscous boundary layer thicknesses are established to quantify the flow development at different stages and over a wide range of flow parameters. Details of the scaling analysis and the numerical procedures are described in this paper.