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Dr Alireza Keshavarzy

Image of Alireza Keshavarzy
Visiting Fellow, School of Civil and Environmental Engineering
Core Member, Centre for Built Infrastructure Research
Master of Engineering Science in Structural Engineering, PhD Civil Engineering
 
Phone
+61 2 9514 2286
Can supervise: Yes

Chapters

Keshavarzy, A. & Ball, J.E. 2011, 'Stochastic Nature of Flow Turbulence and Sediment Particle Entrainment over the Ripples at the Bed of Open Channel Using Image Processing Technique' in Faruk Bhuiyan (ed), Sediment Transport â Flow Processes and Morphology, InTech, Croatia, pp. 69-92.
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Conferences

Sorourian, S., Keshavarzi, A., Samali, B. & Ball, J. 2014, 'Prediction of Scouring Depth at the Outlet of Partially Blocked Box Culvert', World Environmental and Water Resources Congress 2014: Water Without Borders - Proceedings of the 2014 World Environmental and Water Resources Congress, pp. 1352-1361.
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© 2014 American Society of Civil Engineers. Culverts are built at a location in a waterway that crosses a road or railway. The narrowing cross section of waterway creates a limitation to flow passage and therefore blockage occurs during flood events with accumulation of debris at the inlet. The blockage of the culvert can accelerate bed scouring and consequently causes failure of the culvert. It subsequently produces high damage to private properties and public assets. This article concerns scouring at the outlet of partially blocked culverts. In this context the blockage of culverts is studied as an important factor in the scouring pattern of culverts. Therefore, experimental tests were conducted to investigate the effects of culverts blockage on scouring downstream of a culvert. The experimental program was designed to investigate the relationship between the maximum scour depth, blockage ratio of the culvert, and flow characteristics. The experimental tests were carried under nonblocked and partially blocked conditions. The sediment material used in this study was uniform noncohesive sand particles. Results showed that the scoured area and maximum scour depth increases in partially blocked condition compared with the nonblocked condition. The results were compared with the previous developed models, and it was found that the previous model predicts scouring depth less than the scouring depth at blocked condition.
Sorourian, S., Keshavarzi, A., Ball, J. & Samali, B. 2014, 'Location of the maximum scouring depth at the outlet of partially-blocked and non-blocked box culvert', Proceedings of the International Conference on Fluvial Hydraulics, RIVER FLOW 2014, pp. 1475-1480.
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Among various hydraulic structures, culvert is the most likely one which usually blocks by the debris that are carrying by flow during large flood events. The size of the structure and its location where a waterway crosses a road or railway increases the possibility of clogging. The blockage of culvert accelerates bed scouring at the outlet hence affects bed scouring profile. This leads to increase the risk of culvert collapsed and produce different kinds of damages to the society. The present study concerns the effect of upstream blockage on the scouring profile at the outlet of a box culvert. Therefore, the experimental program was designed to investigate the relationship between the scouring geometry and blockage ratio. The experimental tests were carried out under non-blocked and partially blocked conditions. The sediment material used in this study was uniform non-cohesive sand material. Results showed that the scouring bed profile is different in partially blocked condition when compared to the non-blocked condition. Additionally it was found that the maximum scouring depth in a partially blocked culvert occurred at a distance very close to the outlet of the box culvert. © 2014 Taylor & Francis Group, London.
Sorourian, S., Keshavarzy, A., Ball, J.E. & Samali, B. 2013, 'Study of Blockage Effect on Scouring Pattern Downstream of a Box Culvert under Unsteady Flow', Proceeding of the 35th IAHR World Congress, 35th IAHR, Tsinghua University Press, Chengdu, China, pp. 1-9.
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Keshavarzy, A. & Ball, J.E. 2013, 'Study of coherent turbulent flow over the ripples using Particle Image Velocimetry', Proceedings Of The 12'" International Symposium On River Sedimentation - Advances in River Sediment Research, Advances in River Sediment Research, Taylor & Francis Group, Tokyo, Japan, pp. 1101-1105.
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The structure of turbulent flow over ripples is important to understand initiation of sediment entrainment and transport. The focus of this study is the measurement and analysis of the dominant bursting events and the flow structure over the ripples in the bed of a channel. One type of ripple with sinusoidal form was tested in this study. The velocities of flow over the ripples were measured in three dimensions using Particle Image Velocimetry (PIV). These velocities were measured at different points within the flow depth from the bed and at different longitudinal positions along the flume. It was found that upstream of the ripple crest, transition probability of stable organization (P44) were dominant when compared to other 15 transition probabilities. This can be interpreted as an expectation that entrainment should occur at this location. However, downstream of the ripple crest, transition probability of zone 2 to zone 3 (P23) and transition probability of zone 3 to 4 (P34) were more dominant than others. Therefore would be expected sedimentation to occur at this location.
Keshavarzy, A. & Ball, J.E. 2013, 'PIV measurements of coherent turbulent flow structure and bursting process around a scour hole', PROCEEDINGS OF THE 12'" INTERNATIONAL SYMPOSIUM ON RIVER SEDIMENTATION, ISRS - Advances in River Sediment Research, Advances in River Sediment Research, Taylor & Francis Group, Tokyo, Japan, pp. 1093-1100.
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The results of a series of experimental tests related to the flow characteristics in a scouring hole are presented in this paper. The experimental tests were carried out for five different stages of development of a scour hole. These stages are defined on the basis of experimental observation. The mechanisms of the development of the scour hole and flow characteristics were investigated in this study. The flow velocities were measured using Particle Image Velocimetry to characterize the mean velocity field and turbulent characteristics of flow in the scour hole. The measurements reveal a good understanding of the flow characteristics and bursting process and a strong recirculation in the hole. The results showed that upstream of the orifice, the transition probabilities of the stable events were higher than other transition probabilities. Therefore, the events of P11, P22, P33 and P44 were dominant when compared to others. This can be interpreted as an expectation that entrainment should occur at this location. These expectations are consistent with scour hole development and were confirmed by measuring scour hole depth upstream of the orifice.
Sorourian, S., Keshavarzi, A., Samali, B. & Ball, J. 2013, 'Study of blockage effect on scouring pattern downstream of a box culvert', From Materials to Structures: Advancement Through Innovation - Proceedings of the 22nd Australasian Conference on the Mechanics of Structures and Materials, ACMSM 2012, pp. 741-744.
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This experimental study is concerning with the scouring at the outlet of a box culverts. The blockage of culverts has considered as an important factor on the scouring pattern at the outlet of the box culverts. To investigate the effect of blockage on scouring pattern at the downstream of box culvert, some experimental tests were carried out in a laboratory flume located in the Hydraulic Laboratory of University of Technology Sydney (UTS). The experimental tests were carried on in both blocked and non-blocked conditions and consequentially the effect of blockage on depth of scour hole is investigated. It was found that for flow with Froude number of 0.09 there is a 15% increase in the depth of scour hole for a box culvert with 40 precent blockage. Furthermore, the scour depth in blocked condition with the Froude number of 0.12 was 22% deeper than box culvert with non-blocked condition. © 2013 Taylor & Francis Group.
Keshavarzy, A. & Ball, J.E. 2012, 'PIV study of turbulent flow around a circular bridge pier using fractal scaling', Hydrology and water resources symposium 2012, Engineers australia, Sydney, Australia, pp. 1604-1609.
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The flow structure around a bridge pier is complicated, particularly in the flow immediately downstream of a bridge pier. In the study reported herein, the fractal dimensions of velocity fluctuations (u, v) were investigated. Two dimensional velocity fluctuations at horizontal surface were measured using Particle Image Velocimetry (PIV). At each horizontal surface, 700 pairs of images were captured at a frequency of 15 Hz. The time interval between two frames in a pair of captured frames was 10 m seconds. The fractal dimensions were computed using a Fractal Interpolation Function (FIF) algorithm. From the results, it was found that the fractal dimensions fluctuated significantly in the streamwise and transverse flow directions in the vicinity of the pier. A symmetrical pattern of the fractal dimension was found at the rear of the bridge pier. Furthermore, it was found that the fractal dimensions of velocity fluctuations increased rapidly at vicinity of pier at downstream whereas it decreased far from the pier. Therefore, it can be concluded that the fractal dimension using FIF well describes the flow structure around bridge pier.
Keshavarzy, A. & Ball, J.E. 2012, 'PIV measurement of coherent flow structure over gravels in a river bed', Hydrology and water resources symposium 2012, Engineers australia, Sydney, Australia, pp. 1610-1617.
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An experimental study of the role of coherent structures and their effect on initiation of sediment particles has been carried out using a laboratory flume. Experiments were conducted under different flow conditions and fixed bed. Spherical gravels with diameter of 65 mm were installed at the bed of flume. The spherical gravels exposed 20 mm above the bed surface. The two dimensional instantaneous flow velocity was measured simultaneously over the gravels using Particle Image Velocimetry (PIV). The PIV advantage is to measure instantaneous information of coherent flow structure in time and space simultaneously. Quadrant analysis of two instantaneous flow structures revealed a dominant sweep event at above the particles whereas inward Interactions was found low probable event above the spherical particles. The higher inclination angle was also found for sweep events which are likely to induce higher momentum than other events. The results of this study are useful to define entrainment of sediment particles at the bed of river.
Keshavarzi, A. & Ball, J. 2012, 'Statistical analysis of fractal scaling for flow structure around circular bridge pier', River Flow 2012 - Proceedings of the International Conference on Fluvial Hydraulics, pp. 921-926.
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In the paper, the structure of flow is investigated using fractal scaling of 3-D velocity fluctuations and the Reynolds shear stresses around a bridge pier. The fractal dimensions were computed using a Fractal Interpolation Function algorithm. The velocity data were collected in a series of experimental test within a laboratory flume. Three dimensional velocity fluctuations were measured at a number of grid points around a bridge pier using an Acoustic Doppler Velocity meter (Micro-ADV). At each point, 6000 velocity samples were captured at a frequency of 50 Hz. The statistical analysis of fractal dimension shows that the average fractal dimensions reduced from centreline of the flume to the wall, but standard deviations of fractal dimensions increased significantly in the longitudinal and transverse flow directions in the vicinity of the pier. © 2012 Taylor & Francis Group.
Keshavarzi, A., Khabbaz, H. & Ball, J. 2012, 'Scouring depth around arch spur dike at river banks', River Flow 2012 - Proceedings of the International Conference on Fluvial Hydraulics, pp. 689-691.
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Spur dikes are structures, which are normally designed to prevent river banks from scouring. In this study, three sequential spur dikes with zero height above the bed were installed at one side of an experimental flume with a rectangular cross-section. The top of spur dikes was set at same level as the bed level. Sequential spur dikes were tested with four different spaces. The bed of the flume was covered with sand particles of median particle size (D50) equals to 0.85 mm. The experimental tests were carried out under different flow conditions and after achieving equilibrium bed scouring condition, the topography of the bed was measured. The velocity of flow at some points was measured using Acoustic Velocimeter (Micro-ADV). According to the results, it was found that the maximum scouring depth varies significantly with the spacing. Additionally, three regression equations were suggested here to determine maximum scouring depth around first, second and third spur dikes. The above findings can be a useful guideline for design of scouring protections in river training works. © 2012 Taylor & Francis Group, London.
Keshavarzy, A., Ball, J.E. & Moghadam, M.K. 2012, 'FLOW STRUCTURE AND SAFE REGION FOR FISH HABITAT IN RIVERS', 9th international symposium on ecohydraulics 2012, ISE 2012 Vienna, IAHR, Austria, pp. 1-8.
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In large rivers, the life of animals including fish is at risk due to establishment of some hydraulic structures like dams and weirs. Few fish habitat activities including the installation of rocks, rock clusters, rock weirs and other instream works have been done in rivers to minimize the problem. The most important advantage of the habitat structures are their downstream hydraulic condition such as large depth and smaller velocity. These hydraulic conditions provide an area for fish to rest and to feed. In this study, to determine the fish habitat safe region area, evaluations were done in laboratory flume to simulate natural conditions. A quartersphere made of concrete was installed at the bed of flume and then flow velocity in two directions was measured using small electromagnetic velocimeter and PIV. To find the geometry of safe region behind a quarter-sphere the streamlines, contour vectors, location and size of safe region was determined. By drawing the contour lines of velocity and detection of contour vectors, location and size of safe region, it was found that close to the body, the safe region is located adjacent to the bed, and far away from the body. Furthermore, it is concluded that far away from the body, safe region is located in upper depths and by moving toward body peak, safe region area decreases.
Shrestha, C.K., Keshavarzi, A., Khabbaz, H. & Ball, J. 2012, 'Experimental study of the flow structure interactions between Bridge Piers', Proceedings of the 34th Hydrology and Water Resources Symposium, HWRS 2012, pp. 308-315.
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© 2012 Engineers Australia. The detailed study of three dimensional flow structures around two bridge piers is presented in this paper. Eight sets of laboratory experiments were carried out with no pier, a single pier and two piers with different spacing between piers. Two bridge piers were aligned in the direction of flow and at the centre of a laboratory flume. The experimental tests were performed in a flume with 19 m length, 0.61 m wide and 0.60 m deep, under different flow conditions. Three dimensional flow velocities were captured at different grid points and different depths within the flow using a micro Acoustic Doppler Velocimeter (ADV). The velocity was captured at a frequency of 50Hz. The contour plots of three velocity components, turbulence intensities, Reynolds shear stresses and the turbulence kinetic energy as well as the vector plot and flow streamlines were presented in this paper. It was found that significant flow structure interactions are generated with increasing the spacing between the piers. In addition, the results indicated that the flow structure between the piers and at the downstream side of the piers varied significantly. Furthermore, it was found that when the spacing between bridge piers is increased, the effect of the upstream pier starts decreasing and eventually each piers act as an individual pier.
Keshavarzy, A. & Ball, J.E. 2012, 'STATISTICAL ANALYSIS OF TEMPORAL VECTOR ANGLE VARIATIONS AND ITS CHARACTERISTICS IN TURBULENT FLOW', 18th congress of the Asia and Pacific division of international association for hydro-environment engineering and research 2012, hydro-environmental engineering toward harmony between human and nature, IAHR, Korea, pp. 1-8.
Entrainment of sediment particles is stochastic in nature due to the instantaneous fluctuation of velocity fluctuations and turbulent shear stress. The temporal variations of turbulent flow are a very important characteristic for sediment entrainment particularly at low shear stress. To characterise the temporal variation, the velocity vector angles in two imensions are investigated in this experimental study. Data for this study was obtained from three dimensional flow velocities measured in an experimental flume using an Acoustic Doppler Velocimeter (Micro-ADV).This data was analysed to calculate the instantaneous vector angles of the turbulent velocities. The changes in vector angles (?θ) at sequential time steps were calculated also. A statistical analysis of the values of ?θ obtained from the different experimental tests was undertaken. The resultant statistical characteristics were found to be a good representation of the characteristics of movement between quadrants of the turbulence. Also the results indicated that standard deviation of vector angles changed with flow depth from the bed to the free surface.
Keshavarzy, A., Mohammadi, G. & Ball, J.E. 2011, 'Stochastic Modelling of Bursting Process at Threshold Conditions', Proceedings of the 34th IAHR World Congress: Balance and Uncertainty - Water in a Changing World, Conference on Hydraulics in Water Engineering (10th : 2011 : Brisbane, Qld.), Engineers Australia, Brisbane, Australia, pp. 3553-3560.
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In this paper, a stochastic model for analysis of the occurrence of bursting events and entrainment of sediment particles from the bed at the threshold of sediment motion is presented. This study focused on the modeling of turbulent bursts (i.e., the cycle of sweeps, ejections, and inward and outward interactions). From the collected experimental data, a transition probability is presented using Markov process. Using this information about bursting events, a Markov model is presented for the incipient motion of sediment particles. Validation of this model for particle motion was obtained using an image processing technique. Good agreement was found between the predicted number of entrained sediment particles and the observed numbers of particles.
Esfahani, F.S., Keshavarzy, A. & Zia Hosseinipour, E. 2011, 'Turbulent characteristics inside ingoing multi-bend rivers', PROCEEDINGS OF THE 2011 CONGRES - World Environmental and Water Resources Congress 2011: Bearing Knowledge for Sustainability, World Environmental and Water Resources Congress 2011: Bearing Knowledge for Sustainability, ASCE, Palm Springs, California, USA, pp. 4075-4086.
Understanding flow structure inside meandering rivers with different physical properties can be very important to river bank protection, design the artificial canals and also numerical simulations. The effect of different curvatures and also sequential bends on turbulent characteristics are studied in detail for ingoing river meanders. Two physical models of meandering river present strongly curved and mild bends were designed. The models were installed inside a 15 m length flume, separately. Each river meander model consists of three sequential bends and experimental tests were performed inside the second bend. The three-dimensional velocity of flow in five cross-sections of each model was measured in 720 nodal points using Micro-acoustic Doppler velocity meter (ADV). At each nodal point, 6000 velocity data for each direction were stored in a computer. Reynolds shear stress, turbulent kinetic energy and turbulent intensity were analyzed. On the basis of these experiments, the effect of centrifugal force of previous and next bends on flow structure of second bend in the strongly curved multi-bend is stronger than mild's. The present result can also be useful to predict the bed topography.
Niknia, N., Keshavarzy, A. & Zia Hosseinipour, E. 2011, 'Improvement the Trap Efficiency of Vortex Chamber for Exclusion of Suspended Sediment in Diverted Water', PROCEEDINGS OF THE 2011 CONGRES - World Environmental and Water Resources Congress 2011: Bearing Knowledge for Sustainability, World Environmental and Water Resources Congress 2011:Bearing Knowledge for Sustainability, American Society of Civil Engineers (ASCE), Palm Springs, California, USA, pp. 4124-4134.
Deposition of sediment particles in irrigation canals is an important problem in water conveyance systems. From the hydropower point of view, all projects constructed or going to be constructed will have a sedimentation problem sooner or later. The vortex settling chamber is used to separate sediments particles from the diverted water. This type of chamber is self-flushing during the operation. The turbulence of flow that results in eddies keeps the particle in suspension while gravitational force thwarts it. Some of the eddies keeping the particles in suspension are in the bed of the chamber. Therefore, to improve trap efficiency, fully circular deflector should be placed upon the inlet jet. Two sediment feeders were designed; one, based on the sand-clock idea for uniform sediment and second to produce nonuniform sediment. The sediment feeding rate was selected at constant rate of 100 g/s. The sediment size was also selected to be between 0.08 and 2.0 mm. To collect the sediment particles from the flushing orifice (at the central bottom of vortex settling basin) and overflow weir during the experimental tests, the excluded sediments were trapped in two fabric bags and weighed accurately after drying. The model was tested for anticlockwise flow condition. It was found that the trap efficiency of the vortex settling chamber was about 88% for the median particle size of 0.35mm used in this study. To understand the flow structure inside the model under the deflector with clear water flow, the flow velocity in three directions was measured using ADV.
Keshavarzy, A. & Esfahani, F.S. 2011, 'Spatial variation of coherent turbulent flow structure inside ingoing multi-bend river meander', Proceedings of the 34th IAHR World Congress: Balance and Uncertainty - Water in a Changing World, International Association of Hydraulic Engineering & Research, Engineers Australia, Brisbane, Australia, pp. 3545-3552.
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In this paper the effect of different curvatures on spatial variation of coherent flow structure and bursting events inside two multi-bend meanders models with the strong and mild curved are investigated. Two models with three sequential meanders were built and three dimensional flow velocities at five cross sections were measured using Micro-ADV. Based on orthogonal analysis of three dimensional flow velocity, bursting events are classified into two classes and eight zones. The results indicated that the effect of curvature in sequential bends is obvious in model 1. In two models, the occurrence probabilities of sweep and ejection events are higher than outward and inward interactions. The minimum contribution probability is found for zone III-B. The above results can be useful to find meandering pattern inside the rivers and also for river training works.
Keshavarzi, A. & Ball, J. 2011, 'Transition probability of the coherent turbulent flow around a circular bridge pier', World Environmental and Water Resources Congress 2011: Bearing Knowledge for Sustainability - Proceedings of the 2011 World Environmental and Water Resources Congress, pp. 2478-2487.
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The coherent structure of flow around a single circular bridge pier and its effects on bed scouring pattern is investigated in this study. The bursting events and associated shear stresses play a major role in sediment entrainment from the bed and in particular around a bridge pier. In this study, the three-dimensional velocity of flow was measured at 102 points near the bed of an open channel using Acoustic Doppler Velocity meter (Micro-ADV). The pattern of scouring and bed profile was measured during the experimental test. The three-dimensional analyse of bursting process and Markov process was applied to the velocity data to find the sequential occurrence of bursting events and to recognize the transition probability of internal and external sweep events. The results showed that external sweep event was very effective mechanism for sediment entrainment close around a single circular bridge. © 2011 ASCE.
Keshavarzy, A., Ball, J.E. & Hedayat, N. 2010, 'Study of Flow Structure over the Ripples in the Bed of Open Channel', Proceedings: The 6th International Symposium on Management, Engineering and Informatics: MEI 2010 (In the Context of The 14th Multi-conference on Systemics, Cybernetics and Informatics: WMSCI 2010), International Symposium on Management, Engineering and Informatics: MEI, International Institute of Informatics and Systemics (IIIS), Florida, USA, pp. 1-6.
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The structure of turbulent flow over the ripples in an open channel is very important for sediment entrainment and transport and it is a flow characteristic that is not completely understood at present. In this study, the flow structure over ripples was investigated experimentally. To investigate flow structure, the velocity of flow over the ripples in an open channel was measured in three dimensions using an Acoustic Doppler Velocity meter (Micro-ADV). The velocity of the flow was measured at 128 points in the flow with a sampling rate of 50 samples per second. The time averaged flow velocities in the longitudinal and vertical directions were computed prior to analysis of velocity fluctuations to find the contribution of the bursting events into Reynolds shear stress. Presented herein is a discussion of the contribution of bursting events and the Reynolds shear stress as determined in this paper.

Journal articles

Sorourian, S., Keshavarzi, A. & Ball, J.E. 2015, 'Scour at partially blocked box-culverts under steady flow', Proceedings of the Institution of Civil Engineers - Water Management, pp. 1-13.
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Culverts are built at locations where a waterway crosses a road or railway and creates a limitation to flow passage. Furthermore, blockage commonly occurs during flood events with accumulation of debris at the culvert inlet. The inlet blockage changes the flow structure at the outlet and may result in culvert failure. Despite this, the impacts of blockage on culvert hydraulics and downstream waterways have not received consideration in the literature. The purpose of this paper is to mitigate this deficiency by reporting on an investigation into scouring at the outlet of partially blocked culverts. Experimental tests were conducted under steady flow to investigate a relationship between the maximum scour depth, blockage ratio of the culvert and the flow characteristics. Both non-blocked and partially blocked conditions were considered. Consideration of the results obtained showed that the scoured area and maximum scour depth increased with partially blocked culverts conditions compared with equivalent non-blocked culverts.
Hamidifar, H., Omid, M.H. & Keshavarzi, A. 2015, 'Longitudinal dispersion in waterways with vegetated floodplain', Ecological Engineering, vol. 84, pp. 398-407.
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Keshavarzi, A., Melville, B. & Ball, J. 2014, 'Three-dimensional analysis of coherent turbulent flow structure around a single circular bridge pier', Environmental Fluid Mechanics, vol. 14, no. 4, pp. 821-847.
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The coherent turbulent flow around a single circular bridge pier and its effects on the bed scouring pattern is investigated in this study. The coherent turbulent flow and associated shear stresses play a major role in sediment entrainment from the bed particularly around a bridge pier where complex vortex structures exist. The conventional two-dimensional quadrant analysis of the bursting process is unable to define sediment entrainment, particularly where fully three-dimensional flow structures exist. In this paper, three-dimensional octant analysis was used to improve understanding of the role of bursting events in the process of particle entrainment. In this study, the three-dimensional velocity of flow was measured at 102 points near the bed of an open channel using an Acoustic Doppler Velocity meter (Micro-ADV). The pattern of bed scouring was measured during the experiment. The velocity data were analysed using the Markov process to investigate the sequential occurrence of bursting events and to determine the transition probability of the bursting events. The results showed that external sweep and internal ejection events were an effective mechanism for sediment entrainment around a single circular bridge pier. The results are useful in understanding scour patterns around bridge piers. © 2014 Springer Science+Business Media Dordrecht.
Sorourian, S., Keshavarzi, A., Ball, J. & Samali, B. 2014, 'Blockage effects on scouring downstream of box culverts under unsteady flow', Australian Journal of Water Resources, vol. 18, no. 2.
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Keshavarzi, A. & Ball, J. 2014, 'Discharge coefficient of sharp-crested side weir in trapezoidal channel with different side-wall slopes under subcritical flow conditions', Irrigation and Drainage, vol. 63, no. 4, pp. 512-522.
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© 2014 John Wiley & Sons, Ltd. In this study, a comprehensive experimental study was performed to find an equation for the estimation of flow discharge over a sharp-crested side weir in a trapezoidal channel. A physical model with side slopes of 1.5, 1, 0.5 and 0 was used and sharp-crested side weirs with different lengths and heights were tested under different flow conditions. In this study, 212 laboratory tests were performed with different side-wall slopes under subcritical flow conditions since the Froude number=0.08-0.80. As a result, using statistical analysis, a linear relationship is proposed here for estimation of the side-weir discharge coefficient in a trapezoidal channel. The new equation is a function of the upstream Froude number, weir height and side-wall slope. The new equation enables estimation of flow discharge over the side weir with consideration of different side slopes. Furthermore, previously proposed discharge relationships for estimation of the discharge coefficient over sharp-crested side weirs were compared with the new equation and experimental data from this study and this comparison is also reported in this paper.
Esfahani, F.S. & Keshavarzy, A. 2013, 'Dynamic mechanism of turbulent flow in meandering channels: considerations for deflection angle', Stochastic Environmental Research And Risk Assessment, vol. 27, no. 5, pp. 1093-1114.
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To find turbulent flow structure inside meandering channels, three physical models of river meanders representing strongly curved bend, mild bend and elongated symmetrical meander loop were tested in this paper. Instantaneous velocity data in three dimen
Keshavarzi, A., Moghadam, M.K. & Ball, J.E. 2012, 'Optimising round-edged entrance of 55° river water intake', Proceedings of the Institution of Civil Engineers: Water Management, vol. 165, no. 1, pp. 9-19.
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An experimental study was undertaken to optimise a 55° round-edged entrance irrigation water intake. The tests were carried out under different flow conditions in a laboratory flume with a rectangular cross-section under closeended and open-ended flow conditions. To improve the efficiency of water intake, its entrance was rounded with three different radii (r): 100, 150 and 200 mm. Two components of flow velocity in transverse and flow directions were measured using an electromagnetic velocity meter. The flow velocity inside the water intake was measured at 390 regular grid points, across three horizontal layers at 30, 60 and 120 mm heights from the bed. The streamlines were drawn from the captured flow velocity, and hence the separation width and length were determined for the different depth levels, from the bed to the water surface. The discharge ratios (Qr) of the main channel to the lateral channel were set equal to 0.25, 0.67, 1.5 and 4. It was found that a 55° water intake with the radius of curvature of r/ Wb=0.8 produced minimum separation size. It was therefore selected as the optimum 55° round-edged entrance water intake.
Keshavarzi, A., Ball, J. & Nabavi, H. 2012, 'Frequency pattern of turbulent flow and sediment entrainment over ripples using image processing', HYDROLOGY AND EARTH SYSTEM SCIENCES, vol. 16, no. 1, pp. 147-156.
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Keshavarzi, A., Gazni, R. & Homayoon, S.R. 2012, 'Prediction of scouring around an arch-shaped bed sill using Neuro-Fuzzy model', Applied Soft Computing, vol. 12, no. 1, pp. 486-493.
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Zahedani, M.R., Keshavarzi, A., Javan, M. & Shahrokhnia, M.A. 2012, 'New equation for estimation of radial gate discharge', Proceedings of the ICE - Water Management, vol. 165, no. 5, pp. 253-263.
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Esfahani, F.S. & Keshavarzi, A. 2011, 'Effect of different meander curvatures on spatial variation of coherent turbulent flow structure inside ingoing multi-bend river meanders', Stochastic Environmental Research and Risk Assessment, vol. 25, no. 7, pp. 913-928.
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Keshavarzy, A., Valizadeh, M. & Ball, J.E. 2010, 'Experimental Study of the Effects of Submerged Dikes on the Energy and Momentum Coefficients in Compound Channel', Engineering, vol. 2, no. 11, pp. 855-862.
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This paper aims to understand the flow structure around submerged dike in the main channel and flood plain of a compound cross section. The study undertaken to develop this understanding was carried out in a laboratory flume using a submerged vane installed at a 90 degree angle to the bank. In order to study the flow structures, the flow velocity was measured using a three-dimensional Acoustic Doppler Velocity meter (micro-ADV) with data collection rate of 50 Hz. These flow velocity measurements were taken at 500 points on a regular grid. As the tests were undertaken with turbulent flow, these conditions were subcritical. Furthermore, all the tests were undertaken using a fixed bed. The results obtained showed that the momentum transfer and the kinetic energy reduced in two directions. Also the energy and momentum coefficients decreased significantly with the installation of the submerged vane inside the main channel. Finally, streamlines were found to deviate from the side walls of channel into the main channel.
Rahman, H.S., Alireza, K. & Reza, G. 2010, 'Application of Artificial Neural Network, Kriging, and Inverse Distance Weighting Models for Estimation of Scour Depth around Bridge Pier with Bed Sill', Journal of Software Engineering and Applications, vol. 03, no. 10, pp. 944-964.
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Keshavarzi, A. & Khaje Noori, L. 2010, 'Environmental protection stability of river bed and banks using convex, concave, and linear bed sills', Environmental Monitoring and Assessment, vol. 171, no. 1-4, pp. 621-631.
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Mianaei, S.J. & Keshavarzi, A.R. 2010, 'Prediction of riverine suspended sediment discharge using fuzzy logic algorithms, and some implications for estuarine settings', Geo-Marine Letters, vol. 30, no. 1, pp. 35-45.
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Mianaei, S.J. & Keshavarzi, A.R. 2010, 'Study of near bed stochastic turbulence and sediment entrainment over the ripples at the bed of open channel using image processing technique', Stochastic Environmental Research and Risk Assessment, vol. 24, no. 5, pp. 591-598.
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Esfahani, F.S. & Keshavarzi, A.R. 2010, 'How far must trees be cultivated from the edge of the flood plain to provide best river bank protection?', International Journal of River Basin Management, vol. 8, no. 1, pp. 109-116.
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Honar, T. & Keshavarzi, A. 2009, 'Effect of rounded-edge entrance on discharge coefficient of side weir in rectangular channels', Irrigation and Drainage, vol. 58, no. 4, pp. 482-491.
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Moghadam, M.K. & Keshavarzi, A.R. 2009, 'An optimised water intake with the presence of submerged vanes in irrigation canals', Irrigation and Drainage, vol. 59, no. 4, pp. 432-441.
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Mianaei, S.J. & Keshavarzi, A.R. 2008, 'Spatio-temporal variation of transition probability of bursting events over the ripples at the bed of open channel', Stochastic Environmental Research and Risk Assessment, vol. 22, no. 2, pp. 257-264.
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Keshavarzy, A. & Ball, J. 1999, 'An application of image processing in the study of sediment motion', Journal of Hydraulic Research, vol. 37, no. 4, pp. 559-576.
The influence of turbulence on the entrainment of sediment particles from a plane mobile bed was investigated using image processing techniques to record sediment particle motion in an experimental flume while simultaneously monitoring the turbulence characteristics of the flow. The importance of the image processing techniques applied arise from the use of the collected images for determination of the area of sediment entrained and the instantaneous particle velocity. A subtraction technique was used to derive the difference between consecutive images, from which the number of particles entrained in an increment of time could be determined. A cross correlation was applied to find if a relation between the number of entrained particles and the instantaneous shear stress in sweep events existed. A significant correlation with was found for this relation. From the results obtained, the exceedance probability of the area entrained was found to correlate with the exceedance probability of instantaneous shear stress in a sweep event. Image processing was found to be a useful technique for the analysis of experimental data and fundamental to this study aimed at investigating the entrainment mechanisms for sediment particles.
Keshavarzy, A. & Ball, J.E. 1997, 'An analysis of the characteristics of rough bed turbulent shear stresses in an open channel', Stochastic Hydrology and Hydraulics, vol. 11, no. 3, pp. 193-210.
Entrainment of sediment particles from channel beds into the channel flow is influenced by the characteristics of the flow turbulence which produces stochastic shear stress fluctuations at the bed. Recent studies of the structure of turbulent flow has recognized the importance of bursting processes as important mechanisms for the transfer of momentum into the laminar boundary layer. Of these processes, the sweep event has been recognized as the most important bursting event for entrainment of sediment particles as it imposes forces in the direction of the flow resulting in movement of particles by rolling, sliding and occasionally saltating. Similarly, the ejection event has been recognized as important for sediment transport since these events maintain the sediment particles in suspension. In this study, the characteristics of bursting processes and, in particular, the sweep event were investigated in a flume with a rough bed. The instantaneous velocity fluctuations of the flow were measured in two-dimensions using a small electromagnetic velocity meter and the turbulent shear stresses were determined from these velocity fluctuations. It was found that the shear stress applied to the sediment particles on the bed resulting from sweep events depends on the magnitude of the turbulent shear stress and its probability distribution. A statistical analysis of the experimental data was undertaken and it was found necessary to apply a Box-Cox transformation to transform the data into a normally distributed sample. This enabled determination of the mean shear stress, angle of action and standard error of estimate for sweep and ejection events. These instantaneous shear stresses were found to be greater than the mean flow shear stress and for the sweep event to be approximately 40 percent greater near the channel bed. Results from this analysis suggest that the critical shear stress determined from Shield's diagram is not sufficient to predict the initiation of motion due...
Keshavarzy, A. & Ball, J.E. 1995, 'Discussion of Incipient motion on non-horizontal slopes, by Chiew and Parker', Journal of Hydraulic Research, vol. 33, no. 5, pp. 723-724.
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