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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
Room
CB11.11.508
Can supervise: Yes

Book 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 ++ Flow Processes and Morphology, InTech, Croatia, pp. 69-92.
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Conference Papers

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', 35th IAHR, Chengdu, China, September 2013 in Proceeding of the 35th IAHR World Congress, ed Zhang, Zhankui;, Tsinghua University Press, Beijing, pp. 1-9.
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Keshavarzy, A. & Ball, J.E. 2013, 'PIV measurements of coherent turbulent flow structure and bursting process around a scour hole', Advances in River Sediment Research, Tokyo, Japan, September 2013 in PROCEEDINGS OF THE 12'" INTERNATIONAL SYMPOSIUM ON RIVER SEDIMENTATION, ISRS - Advances in River Sediment Research, ed Fukuoka et al., Taylor & Francis Group, UK, 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.
Keshavarzy, A. & Ball, J.E. 2013, 'Study of coherent turbulent flow over the ripples using Particle Image Velocimetry', Advances in River Sediment Research, Tokyo, Japan, September 2013 in Proceedings Of The 12'" International Symposium On River Sedimentation - Advances in River Sediment Research, ed Fukuoka et al., Taylor & Francis Group, UK, 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.
Sorourian, S., Keshavarzy, A., Samali, B. & Ball, J.E. 2013, 'Study of Blockage Effect on Scouring Pattern Downstream of a Box Culvert', Australasian Conference on the Mechanics of Structures and Materials, Sydney, Australia, December 2012 in From materials to structures: Advancement through innovation - Proceedings of the 22nd Australasian Conference on the Mechanics of Structures and Materials, ed Samali,B;Attard,M;Song,C, CRC Press/Balkema, London, pp. 741-744.
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ABSTRACT: 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 percent 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.
Shrestha, C.K., Keshavarzy, A., Khabbaz, H. & Ball, J.E. 2012, 'Experimental Study of the Flow Structure Interactions between Bridge Piers', Sydney, Australia, November 2012 in Hydrology and water resources symposium 2012, ed Conference Technical Committee, Engineers australia, Australia, pp. 308-315.
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 imensional 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 treamlines 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, 'PIV study of turbulent flow around a circular bridge pier using fractal scaling', Sydney, Australia, November 2012 in Hydrology and water resources symposium 2012, ed Hydrology and water resources symposium, Engineers Australia, Engineers australia, Australia, pp. 1604-1609.
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', Sydney, Australia, November 2012 in Hydrology and water resources symposium 2012, ed Hydrology and water resources symposium, Engineers Australia, Engineers australia, Australia, pp. 1610-1617.
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.
Keshavarzy, A. & Ball, J.E. 2012, 'Statistical analysis of fractal scaling for flow structure around circular bridge pier', River Flow 2012, Costa Rica, September 2012 in Fluvial hydraulics, ed R.E. Murillo Munoz, CRC press, balkema, Netherland, pp. 921-926.
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.
Keshavarzy, A., Khabbaz, H. & Ball, J.E. 2012, 'Scouring depth around arch spur dike at river banks', River Flow 2012, Costa Rica, September 2012 in Fluvial hydraulics, ed R.E. Murillo Munoz, CRC press, balkema, Netherland, pp. 689-691.
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.
Keshavarzy, A. & Ball, J.E. 2012, 'STATISTICAL ANALYSIS OF TEMPORAL VECTOR ANGLE VARIATIONS AND ITS CHARACTERISTICS IN TURBULENT FLOW', hydro-environmental engineering toward harmony between human and nature, Korea, August 2012 in 18th congress of the Asia and Pacific division of international association for hydro-environment engineering and research 2012, ed Young Oh Kim, IAHR, Jeju Island, 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 ( ++) at sequential time steps were calculated also. A statistical analysis of the values of ++ 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., Ball, J.E. & Moghadam, M.K. 2012, 'FLOW STRUCTURE AND SAFE REGION FOR FISH HABITAT IN RIVERS', ISE 2012 Vienna, Austria, September 2012 in 9th international symposium on ecohydraulics 2012, ed Mader, H., Kraml, J., IAHR, Boku, pp. 1-8.
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.
Keshavarzy, A., Mohammadi, G. & Ball, J.E. 2011, 'Stochastic Modelling of Bursting Process at Threshold Conditions', Conference on Hydraulics in Water Engineering (10th : 2011 : Brisbane, Qld.), Brisbane, Australia, June 2011 in Proceedings of the 34th IAHR World Congress: Balance and Uncertainty - Water in a Changing World, ed Eric M. Valentine, Engineers Australia, 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.
Keshavarzy, A. & Ball, J.E. 2011, 'Transition probability of the coherent turbulent flow around a circular bridge pier', World Environmental and Water Resources Congress, Palm Springs, California, USA, May 2011 in PROCEEDINGS OF THE 2011 CONGRES - World Environmental and Water Resources Congress 2011: Bearing Knowledge for Sustainability, ed R. Edward Beighley and Mark W. Killgore, American Society of Civil Engineers (ASCE), USA, pp. 2478-2487.
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.
Keshavarzy, A. & Esfahani, F.S. 2011, 'Spatial variation of coherent turbulent flow structure inside ingoing multi-bend river meander', International Association of Hydraulic Engineering & Research, Brisbane, Australia, June 2011 in Proceedings of the 34th IAHR World Congress: Balance and Uncertainty - Water in a Changing World, ed Eric M. Valentine, Engineers Australia, Australia, pp. 3545-3552.
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.
Keshavarzy, A., Ball, J.E. & Hedayat, N. 2010, 'Study of Flow Structure over the Ripples in the Bed of Open Channel', International Symposium on Management, Engineering and Informatics: MEI, Florida, USA, June 2010 in 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), ed Barals J, Callaos N, Carrasquero J V, Chu H W, Eshraghian K, Ferrer J, Fonseca D, Hashimoto S, Holmqvist M, Imai M, Jastroch N, Lesso W, Malpica F, McEachron D, Oropeza A, Pineda J M, Sanchez B, Sanchez M, Savoie M J, Tremante A, Welsch F, Zinn C D., International Institute of Informatics and Systemics (IIIS), 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

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
Keshavarzy, A., Karami Moghadam, M. & Ball, J.E. 2012, 'Optimising round-edged entrance of 55 river water intake', 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 close-ended 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 (Q r) 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/W b = 0-8 produced minimum separation size. It was therefore selected as the optimum 55- round-edged entrance water intake.
Keshavarzy, A., Ball, J.E. & 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.
River channel change and bed scourings are source of major environmental problem for fish and aquatic habitat. The bed form such as ripples and dunes is the result of an interaction between turbulent flow structure and sediment particles at the bed. The structure of turbulent flow over ripples is important to understand initiation of sediment entrainment and its transport. The focus of this study is the measurement and analysis of the dominant bursting events and the flow structure over ripples in the bed of a channel. Two types of ripples with sinusoidal and triangular forms were tested in this study. The velocities of flow over the ripples were measured in three dimensions using an Acoustic Doppler Velocimeter with a sampling rate of 50 Hz. These velocities were measured at different points within the flow depth from the bed and at different longitudinal positions along the flume. A CCD camera was used to capture 1500 sequential images from the bed and to monitor sediment movement at different positions along the bed. Application of image processing technique enabled us to compute the number of entrained and deposited particles over the ripples. From a quadrant decomposition of instantaneous velocity fluctuations close to the bed, it was found that bursting events downstream of the second ripple, in Quadrants 1 and 3, were dominant whereas upstream of the ripple, Quadrants 2 and 4 were dominant. More importantly consideration of these results indicates that the normalized occurrence probabilities of sweep events along the channel are in phase with the bed forms whereas those of ejection events are out of phase with the bed form. Therefore entrainment would be expected to occur upstream and deposition occurs downstream of the ripple. These expectations were confirmed by measurement of entrained and deposited sediment particles from the bed. These above information can be used in practical application for rivers where restoration is required.
Keshavarzy, A., Gazni, R. & Homayoon, 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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In this study, Adaptive Neuro-Fuzzy Inference System (ANFIS) has been used to model local scouring depth and pattern scouring around concave and convex arch shaped circular bed sills. The experimental part of this research study includes seven sets of laboratory test cases which were performed in an experimental flume under different flow conditions. A data set consists of 2754 data points of scouring depth were collected to use in the ANFIS model. The ratio of arch diameter, D, to flume width, W, is used as a non dimensional variables in all test cases. The results from ANFIS model were compared with the results of ANN model obtained by Homayoon et al. [24] and previously presented models. The results indicated that for D/W equal to 1 and 1.2, the ANFIS models produced a good performance for convex and concave bed sills. As a result, the ANFIS models can be used as an alternative to ANN for estimation of scour depth and scour pattern around a concave bed sill installed with a bridge pier.
Zahedani, M., Keshavarzy, A., Javan, M. & Shahrokhnia, M. 2012, 'New Equation For Estimation Of Radial Gate Discharge', Water Management, vol. 165, no. 5, pp. 253-263.
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The flow discharge under a radial gate is a function of the geometric and hydraulic parameters upstream water depth, downstream water depth, gate opening, gate radius and trunnion pin height. A new equation for estimating radial gate discharge for movabl
Esfahani, F.S. & Keshavarzy, 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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In this paper, the effect of different curvatures on the spatial variation of coherent flow structure inside two physical models with both strongly curved and mild multibend meanders is investigated. Three dimensional flow velocities at three sequential meanders were measured using an Acoustic Doppler Velocity meter (Micro-ADV). Three dimensions of flow velocity are classified into two major classes and eight different bursting events. The contribution probability and transition probability of each zone is calculated from experimental data. The results indicated that the effect of curvature in sequential bends was important particularly for strongly curved bends. The contribution probability of the events for strongly curved meanders with relative curvature (Rc/B) of 2.6 were found to be higher than for mild curved meanders with relative curvature (Rc/B) of 4.43. The minimum contribution probability was found in external inward interaction event. In addition, analysis of bursting events showed that the highest values of transition probabilities occurred in the stable organizations for both models. The influences of different curvatures on distributions of the Reynolds shear stress, the turbulent kinetic energy, the streamwise velocity and the vertical velocity were also shown to be in good agreement with eroded bed. The above results can be useful for finding meandering patterns inside rivers and also in river training works.
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.
Keshavarzy, 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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River bed scourings are a major environmental problem for fish and aquatic habitat resources. In this study, to prevent river bed and banks from scouring, different types of bed sills including convex, concave and linear patterns were installed in a movable channel bed in a laboratory flume. The bed sills were tested with nine different arrangements and under different flow conditions. To find the most effective bed sill pattern, the scouring depth was measured downstream of the bed sill for a long experimental duration. The scour depth was measured at the middle and at the end of each experimental test for different ratios of the arch radius to the channel width (r/w). The experimental results indicated that the convex pattern with r/w = 0.35 produced minimum bed scouring depth at the center line whereas the concave pattern with r/w = 0.23 produced the minimum scour depth at the wall banks. Therefore, the convex pattern was the most effective configuration for prevention of scouring at the center line of the river while the concave pattern was very effective to prevent scouring at the river banks. These findings can be suggested to be used in practical applications.
Mianaei, S. & Keshavarzy, A. 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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The ability of fuzzy logic algorithms to model relationships between stream flow and suspended sediment discharge was investigated using daily measurements of stream flow and suspended sediment discharge for the Escanaba River mouth station, situated on the shore of Lake Michigan and operated by the US Geological Survey. Three different configurations of inputs were applied, whereby the inputs were fuzzified into fuzzy subsets of variables by means of triangular membership functions. The relationships between inputs and suspended sediment discharge (output) were represented by a set of fuzzy rule expressed in IF++THEN format. The weighted average method served for defuzzification. The commonly used sediment rating curve was also applied to the data, and its performance compared with that of the three models by means of statistical analyses. For all three models, suspended sediment discharge predicted by the fuzzy logic algorithm was in satisfactory agreement with observations. Furthermore, the fuzzy logic algorithms performed better than the sediment rating curve, particularly at higher rates of suspended sediment discharge (in this study, more than 50++106g/day). Considered collectively, the use of fuzzy logic algorithms is suggested as a simple and effective approach for better prediction of suspended sediment discharge, also for estuaries.
Mianaei, S. & Keshavarzy, A. 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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In this study, the coherent structure in near bed bursting events over the ripples and mechanism of sediment bed load transport were investigated experimentally. The experiments in this study were carried out in the laboratory flume, in two parts; fixed bed ripple and mobile bed ripple. Tow artificial ripples, were built and used for making both fixed and mobile bed. For the fixed bed part, velocity fluctuations were measured using an Acoustic Doppler Velocimeter. In order to apply bursting analysis for obtained data, a computer programwas written in visual basic language. Then, variation of turbulence shear stress associated with different bed form geometries was determined and mechanism of sediment transport by ripple shape at the bed of open channel was investigated. For the mobile bed part, artificial ripples were used as mould to make ripples. An image processing technique was used to record amount of sediment particles which are entrained and deposited over the same selected points at the fixed bed part. Results of mobile bed part, confirmed the results of shear stress analysis of fixed bed part.
Homayoon, R., Keshavarzy, A. & Gazni, R. 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. 3, no. 10, pp. 944-964.
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This paper outlines the application of the multi-layer perceptron artificial neural network (ANN), ordinary kriging (OK), and inverse distance weighting (IDW) models in the estimation of local scour depth around bridge piers. As part of this study, bridge piers were installed with bed sills at the bed of an experimental flume. Experimental tests were conducted under different flow conditions and varying distances between bridge pier and bed sill. The ANN, OK and IDW models were applied to the experimental data and it was shown that the artificial neural network model predicts local scour depth more accurately than the kriging and inverse distance weighting models. It was found that the ANN with two hidden layers was the optimum model to predict local scour depth. The results from the sixth test case showed that the ANN with one hidden layer and 17 hidden nodes was the best model to predict local scour depth. Whereas the results from the fifth test case found that the ANN with three hidden layers was the best model to predict local scour depth.
Esfahani, F.S. & Keshavarzy, A. 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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In this study, to find the best location to cultivate the trees for river bank protection, some experimental tests were performed. One row of trees were cultivated at five different distances from the main channel/floodplain interface in a rectangular compound open channel. In experimental model for simulating the trees, some cylindrical wood rods were attached to the bed of flood plain. The three-dimensional flow velocity of flow in a cross-section between the trees were measured in 149 nodal points using Micro-acoustic Doppler velocimeter (ADV) velocity meter. At each nodal point, 6000 velocity data for each direction were stored in a computer. From the analysis of the experimental data, it was concluded that upon cultivating trees at 10% distance of flood plain width from the edge of main channel, the minimum streamwise velocity occurred near main channel/floodplain interface, while the maximum streamwise velocity occurred far from the edge of floodplain. Therefore, the best location for cultivating the trees was found to be at 10% of floodplain width and it is suggested for river bank protection in practical applications.
Moghadam, M.K. & Keshavarzy, A. 2010, '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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One of the problems at most water intakes is accumulation of sediment at the entrance and changing of flow talweg path at the water intake. Submerged vanes are small hydraulic structures that are used for flow and sediment control on the bed of rivers. The submerged vanes may be installed individually or in a group with different arrangements. In this study, a group of submerged vanes are installed at the entrance of a rounded edge 558 water intake with parallel and zigzag arrangements. The vanes++ installation angles were selected to be 10, 20, 30 and 408 to the flow direction. The sedimentation pattern at the entrance of the water intake and the amount of sediment entering into the lateral channel were measured after experimental tests. From the experimental study, the optimum vane angle for the above-specified water intake was found to be 308. Also the parallel arrangement was found to be the best arrangement for the submerged vane.
Honar, T. & Keshavarzy, 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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Side weirs are flow diversion devices that are widely used in irrigation and drainage networks and urban sewage systems. They are usually built with a squared-edge entrance. The present study focuses on the effect of rounded-edge entrance shape on the discharge coefficient of a side weir under subcritical flow condition in rectangular channels. In this study, 90 laboratory tests were conducted and the results were analyzed to find the influence of non-dimensional hydraulic parameters on the discharge coefficient. From the results, it was found that under subcritical flow condition the side weir with rounded-edge entrance discharges 10% more flow rate than the squared edge entrance. As a result, for equal flow rate, the rounded-edge entrance side weir with small dimensions can be designed for use in practical applications.
Mianaei, S. & Keshavarzy, A. 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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In this study, the turbulent flow structure over the ripples at the bed of open channel was investigated experimentally. An analysis of bursting process was used to recognize the susceptible regions for sediment entrainment and deposition over the ripples. Two artificial ripples were built according to the ripples, formed by nature. Three different configurations of ripples were used by changing the wavelength. According to analysis of bursting event it was found that at the stoss side of ripples, quadrants (II) and (IV) were dominant to the quadrants (I) and (III) and at the lee side of the ripple it was vice versa. Also the transition probabilities of the bursting events were determined. The results showed that stable organizations of each class of the events had highest transition probabilities whereas cross organizations had lowest transition probabilities. Additionally, an effort was made to find the average inclination angle of the bursting events in quadrants (II) and (IV). The results showed that the mean angle of events in quadrants (II) and (IV) increases at the downstream of stoss side to the crest in each experimental test. Also, at the lee side where the sediment particles were deposited, the inclination angles had the highest values.