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Amir Zarrati

AmirKabir University Of Technology, Civil and Environmental Engineering, Faculty Member

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Prof. of Hydraulic Eng. interested in numerical and physical modeling of complex flow behavior such as scouring in rivers, two phase air-water flow, sediment transport, reservoir sedimentation and prevention.

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University of Bristol

Michele Barbato

University of California, Davis

Tufts University

Bjørn-Oliver Magsig

Victoria University of Wellington

Patricia Wouters

Xiamen University

Tadesse Kassa Woldetsadik

Addis Ababa University

Hasanuddin University

Utah State University

Addis Ababa University

Idris Mandang, Dr. Eng

Mulawarman University

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Papers by Amir Zarrati

Effect of Side Looking Acoustic Doppler Velocimeter (ADV) Presence on Turbulent Flow Field in Compound Channel

Modares Mechanical Engineering, Dec 10, 2019

Study on scouring around bridge piers protected by collar using low density sediment

International Journal of Civil Engineering, Sep 10, 2013

Mathematical modelling of air-water mixtures in open channels

Journal of Hydraulic Research, Sep 1, 1994

A mathematical model was developed to predict the air concentration profiles in the deaeration zo... more A mathematical model was developed to predict the air concentration profiles in the deaeration zone below a spillway aerator by solving the conservation equations of mass and momentum. The turbulent diffusion coefficient was calculated by a k-ε model and the air-water mixture was treated as a stratified flow. To test the mathematical model a series of experiments was conducted. Air was injected from the bed of a flow channel and air concentration profiles were measured at various downstream sections. From the comparison of the computer predictions with the experimental data it was concluded that the present analytical approach was satisfactory for practical purposes and showed promise for further development.

Application of a Needle Probe in Measuring Local Parameters in Air-Water Flow

In this paper, development of a double needle probe for measuring local parameters in air-water m... more In this paper, development of a double needle probe for measuring local parameters in air-water mixtures is explained. This probe is designed to measure flow velocities up to 10 m/s and bubbles as small as 1 mm. Careful programming made it possible to collect up to 2 minutes of data with a speed of 52 KHz from 2 channel.

کاربرد مدلسازی عددی سهبعدی در شبیهسازی پدیدههای پیچیده مهندسی رودخانه

International Symposium on Algorithms and Computation, May 5, 2013

توسعه مدل عددی برای پیش بینی فشارهای دینامیک در جریان کانال های باز با شبکه منحنی الخط غیرمتعامد

نشریه هیدرولیک, Jan 21, 2012

Numerical Simulation of gated stepped spillway and its Cavitation Potential

A Study on the accuracy of finite volume numerical models with non-rectangular mesh

Scientia Iranica, Feb 8, 2021

In the process of numerical simulation of complex geometries and ow depth variations, non-rectang... more In the process of numerical simulation of complex geometries and ow depth variations, non-rectangular computational cells are generated. However, the application of this type of mesh causes numerical errors. A 3D model, which was veri ed and validated before, was used to shed light on the problem in a simple, open channel ow. A zigzag computational mesh was used to study the e ect of non-rectangular cells on the accuracy of the model. Results showed that water surface and velocity pro les oscillated around the correct answer. Investigating the reason for this oscillation showed that assuming constant velocity on non-rectangular computational cell surfaces, which is a usual practice in all numerical schemes, cause this error. Variation of velocity on mesh surfaces was then added to the computation model and as a result, the oscillations in velocity pro les and water surface were eliminated. Further analysis showed that this is a general problem in any nite volume method with a non-rectangular mesh.

Application of Multi-Block method for simulating shallow free surface flows in complex geometries

Journal of Hydraulic Research, Sep 1, 2008

In the present study a numerical method is developed for simulating shallow free surface flows in... more In the present study a numerical method is developed for simulating shallow free surface flows in complex geometries. A Multi-Block (MB) method is employed in conjunction with non-orthogonal curvilinear coordinate system. This technique gives the numerical method a high flexibility to tackle flow domains with any complex boundary which may be encountered in nature. The MB method utilizes patched grid with continuous grid lines across block boundaries. In this paper the MB methods is applied to 2-D shallow flows. However, this technique is extendable to 3-D models too. The model is based on collocated grid arrangement and the control volume method is used for solution of equations. The method is implicit and uses a SIMPLEC-like algorithm to find the water surface elevation. The flexibility and accuracy of the model is presented in few test cases with complex block arrangement and circulating flows. RÉSUMÉ Dans la présente étude une méthode numérique est développée pour simuler les écoulements peu profonds à surface libre dans les géométries complexes. On utilise conjointement une méthode multi-blocs et un système de coordonnées curvilignes non-orthogonales. Cela permet une grande souplesse pour traiter les domaines d'écoulement quelle que soit la complexité des frontières rencontrées en nature. La méthode multi-blocs utilise un maillage rapiécé avec des lignes de maillage continues à travers les frontières de bloc. Dans cet article la méthode multi-blocs est appliquée aux écoulements 2-D peu profonds. Mais cette technique est également applicable aux modèles 3-D. Le modèle est basé sur une disposition de grille colocalisée et on utilise la méthode du volume de contrôle pour la solution des équations. La méthode est implicite avec un algorithme de type SIMPLEC pour déterminer l'élévation de la surface libre. La souplesse et l'exactitude du modèle sont illustrées par quelques cas tests présentant une certaine complexité dans la disposition des blocs et la circulation des écoulements.

Experimental study on the 3D-flow field of a free-surface vortex using stereo PIV

Journal of Hydraulic Research, Sep 3, 2021

In order to analyse the flow characteristics of free-surface vortexes and to validate the Burgers... more In order to analyse the flow characteristics of free-surface vortexes and to validate the Burgers vortex model by using stereo particle image velocimetry, experiments are conducted in a 600 mm diameter vortex tank. Measured axial velocities indicate that 10-25% of the flow is transported through the vortex core. The velocity profiles show that the axial flow is concentrated in a domain bounded by two times the core radius. Despite Burgers' assumption of radially independent axial velocity profiles, the model quantifies the tangential velocity profile within a relative uncertainty of circa 10%. The measurements show that it seems valid to use Burgers' model to obtain an estimate for the core radius by taking the average axial velocity over a radial domain of approximately 2.2 times the core radius. The Burgers model quantifies the air core depth with an uncertainty of 20% relative to the measurements. When compared with the magnitude of vorticity diffusion by molecular viscosity, the experiments show that there is no significant diffusion by radial turbulence.

A 3D analytical model for vortex velocity field based on spiral streamline pattern

Water science and engineering, Sep 1, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Velocity field in a reservoir in the presence of an air-core vortex

Water management, Jun 1, 2014

Water Management Volume 167 Issue WM6 Velocity field in a reservoir in the presence of an air-cor... more Water Management Volume 167 Issue WM6 Velocity field in a reservoir in the presence of an air-core vortex Sarkardeh, Jabbari, Zarrati and Tavakkol Water Management Volume 167 Issue WM6 Velocity field in a reservoir in the presence of an air-core vortex Sarkardeh, Jabbari, Zarrati and Tavakkol Water Management Volume 167 Issue WM6 Velocity field in a reservoir in the presence of an air-core vortex Sarkardeh, Jabbari, Zarrati and Tavakkol Water Management Volume 167 Issue WM6 Velocity field in a reservoir in the presence of an air-core vortex Sarkardeh, Jabbari, Zarrati and Tavakkol Water Management Volume 167 Issue WM6 Velocity field in a reservoir in the presence of an air-core vortex Sarkardeh, Jabbari, Zarrati and Tavakkol Water Management Volume 167 Issue WM6 Velocity field in a reservoir in the presence of an air-core vortex Sarkardeh, Jabbari, Zarrati and Tavakkol Water Management Volume 167 Issue WM6 Velocity field in a reservoir in the presence of an air-core vortex Sarkardeh, Jabbari, Zarrati and Tavakkol Water Management Volume 167 Issue WM6 Velocity field in a reservoir in the presence of an air-core vortex Sarkardeh, Jabbari, Zarrati and Tavakkol Copyright of Proceedings of ICE: Water Management is the property of Thomas Telford Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.

Application of Multi-Block method for simulating shallow free surface flows in complex geometries Application de la méthode multi-blocs à la simulation des écoulements peu profonds à surface libre dans les géométries complexes

In the present study a numerical method is developed for simulating shallow free surface flows in... more In the present study a numerical method is developed for simulating shallow free surface flows in complex geometries. A Multi-Block (MB) method is employed in conjunction with non-orthogonal curvilinear coordinate system. This technique gives the numerical method a high flexibility to tackle flow domains with any complex boundary which may be encountered in nature. The MB method utilizes patched grid with continuous grid lines across block boundaries. In this paper the MB methods is applied to 2-D shallow flows. However, this technique is extendable to 3-D models too. The model is based on collocated grid arrangement and the control volume method is used for solution of equations. The method is implicit and uses a SIMPLEC-like algorithm to find the water surface elevation. The flexibility and accuracy of the model is presented in few test cases with complex block arrangement and circulating flows. RÉSUMÉ Dans la présente étude une méthode numérique est développée pour simuler les écoulements peu profonds à surface libre dans les géométries complexes. On utilise conjointement une méthode multi-blocs et un système de coordonnées curvilignes non-orthogonales. Cela permet une grande souplesse pour traiter les domaines d'écoulement quelle que soit la complexité des frontières rencontrées en nature. La méthode multi-blocs utilise un maillage rapiécé avec des lignes de maillage continues à travers les frontières de bloc. Dans cet article la méthode multi-blocs est appliquée aux écoulements 2-D peu profonds. Mais cette technique est également applicable aux modèles 3-D. Le modèle est basé sur une disposition de grille colocalisée et on utilise la méthode du volume de contrôle pour la solution des équations. La méthode est implicite avec un algorithme de type SIMPLEC pour déterminer l'élévation de la surface libre. La souplesse et l'exactitude du modèle sont illustrées par quelques cas tests présentant une certaine complexité dans la disposition des blocs et la circulation des écoulements.

Development of mesh-free particle technique for simulation of non-hydrostatic free surface flow

Computers & Fluids, Dec 1, 2014

Comparison between the Lagrangian and Eulerian Approach in Simulation of Free Surface Air-Core Vortices

Water, Mar 7, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more

Computational Fluid Mechanics and Hydraulics

Water, Dec 7, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more

Numerical study of scouring downstream of a stilling basin

Environmental Fluid Mechanics, Feb 23, 2021

The aim of the present study is to numerically investigate the scouring phenomenon downstream of ... more The aim of the present study is to numerically investigate the scouring phenomenon downstream of a stilling basin for a wide range of Froude number and size of bed material. The numerical model was first verified. The results obtained from the numerical model concerning the maximum depth and profiles of the scoured hole were in agreement with the long-term experimental data. Thereupon, the verified numerical model was employed to simulate the profile of the scour hole for various Froude numbers and bed material sizes downstream of the stilling basin. According to the results of the numerical model as well as experimental data, it was revealed that by using dimensionless scour depth, the upstream profile of the scour hole is independent of time and size of the material. Results show that the bottom of the scour hole in the oscillating jump is of greater length than the steady jump. Moreover, both the numerical and available experimental data were used to propose a relationship for calculation of long-term maximum scour depth in a wide range of affecting parameters. Scour hole depth and geometry downstream of a stilling basin were studied with a verified numerical model. Numerical simulations were made in a wide range of Froude number and bed material size which were not available in the literature. Using available experimental data and numerical model results, an equation was developed for estimating the scour depth. Scour hole depth and geometry downstream of a stilling basin were studied with a verified numerical model. Numerical simulations were made in a wide range of Froude number and bed material size which were not available in the literature. Using available experimental data and numerical model results, an equation was developed for estimating the scour depth.

Wall and Bed Shear Force in Rectangular Open Channels

Scientia Iranica, Aug 19, 2017

This paper investigates the e ects of velocity gradients and secondary currents on distribution o... more This paper investigates the e ects of velocity gradients and secondary currents on distribution of the shear force between the walls and bed of rectangular open channels. This paper shows that neglecting the e ect of secondary currents and assuming zeroshear division lines do not yield acceptable results. Then, accordingly, a method was introduced to determine the percentage of the total shear force acting on the walls and bed of rectangular open channels, taking both velocity gradients and secondary currents into account. Using the channel bisectors, along which there is no secondary ows e ect, and orthogonal trajectories to isovels, along which there is no shear stress, the channel's crosssection was divided into three major subsections: bed, wall, and shared areas. The geometry of each subsection was derived with respect to the location of the maximum velocity. The share of the bed and wall shear forces from the shared area were calculated afterwards. The results for bed and walls shear forces are in agreement with the experimental data containing an average relative error of less than 5% for regular ows and the ows carrying suspended sediment. This method also provides a physics-driven range for the wall and bed shear forces, which nicely covers the experimental data.

Development of a Needle Probe for Measurement in Air-Water Flows

Water resources engineering, 1998

Development of an Implicit Numerical Model for Calculation of Sub-And Super-Critical Flows

International Journal of Engineering, Feb 1, 2005

A two dimensional numerical model of shallow water equations was developed to calculate sub and s... more A two dimensional numerical model of shallow water equations was developed to calculate sub and super-critical open channel flows. Utilizing an implicit scheme the steady state equations were discretized based on a control volume method. Collocated grid arrangement was applied with a SIMPLEC like algorithm for depth-velocity coupling. A power law scheme was used for discretization of convection and diffusion terms. Underrelaxation factors were introduced in the model to prevent divergence. Momentum interpolation was used in calculating velocities on cell faces to avoid checker board water surface fluctuation in the collocated grid. The model was verified in different cases including complex water surface profiles and hydraulic jumps. The results are compared with experimental and analytical data and the necessary values of under relaxation factors for a converged solution are discussed. No artificial viscosity was required, which is the advantage of the present model.

Effect of Side Looking Acoustic Doppler Velocimeter (ADV) Presence on Turbulent Flow Field in Compound Channel

Modares Mechanical Engineering, Dec 10, 2019

Study on scouring around bridge piers protected by collar using low density sediment

International Journal of Civil Engineering, Sep 10, 2013

Mathematical modelling of air-water mixtures in open channels

Journal of Hydraulic Research, Sep 1, 1994

A mathematical model was developed to predict the air concentration profiles in the deaeration zo... more A mathematical model was developed to predict the air concentration profiles in the deaeration zone below a spillway aerator by solving the conservation equations of mass and momentum. The turbulent diffusion coefficient was calculated by a k-ε model and the air-water mixture was treated as a stratified flow. To test the mathematical model a series of experiments was conducted. Air was injected from the bed of a flow channel and air concentration profiles were measured at various downstream sections. From the comparison of the computer predictions with the experimental data it was concluded that the present analytical approach was satisfactory for practical purposes and showed promise for further development.

Application of a Needle Probe in Measuring Local Parameters in Air-Water Flow

In this paper, development of a double needle probe for measuring local parameters in air-water m... more In this paper, development of a double needle probe for measuring local parameters in air-water mixtures is explained. This probe is designed to measure flow velocities up to 10 m/s and bubbles as small as 1 mm. Careful programming made it possible to collect up to 2 minutes of data with a speed of 52 KHz from 2 channel.

کاربرد مدلسازی عددی سهبعدی در شبیهسازی پدیدههای پیچیده مهندسی رودخانه

International Symposium on Algorithms and Computation, May 5, 2013

توسعه مدل عددی برای پیش بینی فشارهای دینامیک در جریان کانال های باز با شبکه منحنی الخط غیرمتعامد

نشریه هیدرولیک, Jan 21, 2012

Numerical Simulation of gated stepped spillway and its Cavitation Potential

A Study on the accuracy of finite volume numerical models with non-rectangular mesh

Scientia Iranica, Feb 8, 2021

In the process of numerical simulation of complex geometries and ow depth variations, non-rectang... more In the process of numerical simulation of complex geometries and ow depth variations, non-rectangular computational cells are generated. However, the application of this type of mesh causes numerical errors. A 3D model, which was veri ed and validated before, was used to shed light on the problem in a simple, open channel ow. A zigzag computational mesh was used to study the e ect of non-rectangular cells on the accuracy of the model. Results showed that water surface and velocity pro les oscillated around the correct answer. Investigating the reason for this oscillation showed that assuming constant velocity on non-rectangular computational cell surfaces, which is a usual practice in all numerical schemes, cause this error. Variation of velocity on mesh surfaces was then added to the computation model and as a result, the oscillations in velocity pro les and water surface were eliminated. Further analysis showed that this is a general problem in any nite volume method with a non-rectangular mesh.

Application of Multi-Block method for simulating shallow free surface flows in complex geometries

Journal of Hydraulic Research, Sep 1, 2008

In the present study a numerical method is developed for simulating shallow free surface flows in... more In the present study a numerical method is developed for simulating shallow free surface flows in complex geometries. A Multi-Block (MB) method is employed in conjunction with non-orthogonal curvilinear coordinate system. This technique gives the numerical method a high flexibility to tackle flow domains with any complex boundary which may be encountered in nature. The MB method utilizes patched grid with continuous grid lines across block boundaries. In this paper the MB methods is applied to 2-D shallow flows. However, this technique is extendable to 3-D models too. The model is based on collocated grid arrangement and the control volume method is used for solution of equations. The method is implicit and uses a SIMPLEC-like algorithm to find the water surface elevation. The flexibility and accuracy of the model is presented in few test cases with complex block arrangement and circulating flows. RÉSUMÉ Dans la présente étude une méthode numérique est développée pour simuler les écoulements peu profonds à surface libre dans les géométries complexes. On utilise conjointement une méthode multi-blocs et un système de coordonnées curvilignes non-orthogonales. Cela permet une grande souplesse pour traiter les domaines d'écoulement quelle que soit la complexité des frontières rencontrées en nature. La méthode multi-blocs utilise un maillage rapiécé avec des lignes de maillage continues à travers les frontières de bloc. Dans cet article la méthode multi-blocs est appliquée aux écoulements 2-D peu profonds. Mais cette technique est également applicable aux modèles 3-D. Le modèle est basé sur une disposition de grille colocalisée et on utilise la méthode du volume de contrôle pour la solution des équations. La méthode est implicite avec un algorithme de type SIMPLEC pour déterminer l'élévation de la surface libre. La souplesse et l'exactitude du modèle sont illustrées par quelques cas tests présentant une certaine complexité dans la disposition des blocs et la circulation des écoulements.

Experimental study on the 3D-flow field of a free-surface vortex using stereo PIV

Journal of Hydraulic Research, Sep 3, 2021

In order to analyse the flow characteristics of free-surface vortexes and to validate the Burgers... more In order to analyse the flow characteristics of free-surface vortexes and to validate the Burgers vortex model by using stereo particle image velocimetry, experiments are conducted in a 600 mm diameter vortex tank. Measured axial velocities indicate that 10-25% of the flow is transported through the vortex core. The velocity profiles show that the axial flow is concentrated in a domain bounded by two times the core radius. Despite Burgers' assumption of radially independent axial velocity profiles, the model quantifies the tangential velocity profile within a relative uncertainty of circa 10%. The measurements show that it seems valid to use Burgers' model to obtain an estimate for the core radius by taking the average axial velocity over a radial domain of approximately 2.2 times the core radius. The Burgers model quantifies the air core depth with an uncertainty of 20% relative to the measurements. When compared with the magnitude of vorticity diffusion by molecular viscosity, the experiments show that there is no significant diffusion by radial turbulence.

A 3D analytical model for vortex velocity field based on spiral streamline pattern

Water science and engineering, Sep 1, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Velocity field in a reservoir in the presence of an air-core vortex

Water management, Jun 1, 2014

Water Management Volume 167 Issue WM6 Velocity field in a reservoir in the presence of an air-cor... more Water Management Volume 167 Issue WM6 Velocity field in a reservoir in the presence of an air-core vortex Sarkardeh, Jabbari, Zarrati and Tavakkol Water Management Volume 167 Issue WM6 Velocity field in a reservoir in the presence of an air-core vortex Sarkardeh, Jabbari, Zarrati and Tavakkol Water Management Volume 167 Issue WM6 Velocity field in a reservoir in the presence of an air-core vortex Sarkardeh, Jabbari, Zarrati and Tavakkol Water Management Volume 167 Issue WM6 Velocity field in a reservoir in the presence of an air-core vortex Sarkardeh, Jabbari, Zarrati and Tavakkol Water Management Volume 167 Issue WM6 Velocity field in a reservoir in the presence of an air-core vortex Sarkardeh, Jabbari, Zarrati and Tavakkol Water Management Volume 167 Issue WM6 Velocity field in a reservoir in the presence of an air-core vortex Sarkardeh, Jabbari, Zarrati and Tavakkol Water Management Volume 167 Issue WM6 Velocity field in a reservoir in the presence of an air-core vortex Sarkardeh, Jabbari, Zarrati and Tavakkol Water Management Volume 167 Issue WM6 Velocity field in a reservoir in the presence of an air-core vortex Sarkardeh, Jabbari, Zarrati and Tavakkol Copyright of Proceedings of ICE: Water Management is the property of Thomas Telford Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.

Application of Multi-Block method for simulating shallow free surface flows in complex geometries Application de la méthode multi-blocs à la simulation des écoulements peu profonds à surface libre dans les géométries complexes

In the present study a numerical method is developed for simulating shallow free surface flows in... more In the present study a numerical method is developed for simulating shallow free surface flows in complex geometries. A Multi-Block (MB) method is employed in conjunction with non-orthogonal curvilinear coordinate system. This technique gives the numerical method a high flexibility to tackle flow domains with any complex boundary which may be encountered in nature. The MB method utilizes patched grid with continuous grid lines across block boundaries. In this paper the MB methods is applied to 2-D shallow flows. However, this technique is extendable to 3-D models too. The model is based on collocated grid arrangement and the control volume method is used for solution of equations. The method is implicit and uses a SIMPLEC-like algorithm to find the water surface elevation. The flexibility and accuracy of the model is presented in few test cases with complex block arrangement and circulating flows. RÉSUMÉ Dans la présente étude une méthode numérique est développée pour simuler les écoulements peu profonds à surface libre dans les géométries complexes. On utilise conjointement une méthode multi-blocs et un système de coordonnées curvilignes non-orthogonales. Cela permet une grande souplesse pour traiter les domaines d'écoulement quelle que soit la complexité des frontières rencontrées en nature. La méthode multi-blocs utilise un maillage rapiécé avec des lignes de maillage continues à travers les frontières de bloc. Dans cet article la méthode multi-blocs est appliquée aux écoulements 2-D peu profonds. Mais cette technique est également applicable aux modèles 3-D. Le modèle est basé sur une disposition de grille colocalisée et on utilise la méthode du volume de contrôle pour la solution des équations. La méthode est implicite avec un algorithme de type SIMPLEC pour déterminer l'élévation de la surface libre. La souplesse et l'exactitude du modèle sont illustrées par quelques cas tests présentant une certaine complexité dans la disposition des blocs et la circulation des écoulements.

Development of mesh-free particle technique for simulation of non-hydrostatic free surface flow

Computers & Fluids, Dec 1, 2014

Comparison between the Lagrangian and Eulerian Approach in Simulation of Free Surface Air-Core Vortices

Water, Mar 7, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more

Computational Fluid Mechanics and Hydraulics

Water, Dec 7, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more

Numerical study of scouring downstream of a stilling basin

Environmental Fluid Mechanics, Feb 23, 2021

The aim of the present study is to numerically investigate the scouring phenomenon downstream of ... more The aim of the present study is to numerically investigate the scouring phenomenon downstream of a stilling basin for a wide range of Froude number and size of bed material. The numerical model was first verified. The results obtained from the numerical model concerning the maximum depth and profiles of the scoured hole were in agreement with the long-term experimental data. Thereupon, the verified numerical model was employed to simulate the profile of the scour hole for various Froude numbers and bed material sizes downstream of the stilling basin. According to the results of the numerical model as well as experimental data, it was revealed that by using dimensionless scour depth, the upstream profile of the scour hole is independent of time and size of the material. Results show that the bottom of the scour hole in the oscillating jump is of greater length than the steady jump. Moreover, both the numerical and available experimental data were used to propose a relationship for calculation of long-term maximum scour depth in a wide range of affecting parameters. Scour hole depth and geometry downstream of a stilling basin were studied with a verified numerical model. Numerical simulations were made in a wide range of Froude number and bed material size which were not available in the literature. Using available experimental data and numerical model results, an equation was developed for estimating the scour depth. Scour hole depth and geometry downstream of a stilling basin were studied with a verified numerical model. Numerical simulations were made in a wide range of Froude number and bed material size which were not available in the literature. Using available experimental data and numerical model results, an equation was developed for estimating the scour depth.

Wall and Bed Shear Force in Rectangular Open Channels

Scientia Iranica, Aug 19, 2017

This paper investigates the e ects of velocity gradients and secondary currents on distribution o... more This paper investigates the e ects of velocity gradients and secondary currents on distribution of the shear force between the walls and bed of rectangular open channels. This paper shows that neglecting the e ect of secondary currents and assuming zeroshear division lines do not yield acceptable results. Then, accordingly, a method was introduced to determine the percentage of the total shear force acting on the walls and bed of rectangular open channels, taking both velocity gradients and secondary currents into account. Using the channel bisectors, along which there is no secondary ows e ect, and orthogonal trajectories to isovels, along which there is no shear stress, the channel's crosssection was divided into three major subsections: bed, wall, and shared areas. The geometry of each subsection was derived with respect to the location of the maximum velocity. The share of the bed and wall shear forces from the shared area were calculated afterwards. The results for bed and walls shear forces are in agreement with the experimental data containing an average relative error of less than 5% for regular ows and the ows carrying suspended sediment. This method also provides a physics-driven range for the wall and bed shear forces, which nicely covers the experimental data.

Development of a Needle Probe for Measurement in Air-Water Flows

Water resources engineering, 1998

Development of an Implicit Numerical Model for Calculation of Sub-And Super-Critical Flows

International Journal of Engineering, Feb 1, 2005

A two dimensional numerical model of shallow water equations was developed to calculate sub and s... more A two dimensional numerical model of shallow water equations was developed to calculate sub and super-critical open channel flows. Utilizing an implicit scheme the steady state equations were discretized based on a control volume method. Collocated grid arrangement was applied with a SIMPLEC like algorithm for depth-velocity coupling. A power law scheme was used for discretization of convection and diffusion terms. Underrelaxation factors were introduced in the model to prevent divergence. Momentum interpolation was used in calculating velocities on cell faces to avoid checker board water surface fluctuation in the collocated grid. The model was verified in different cases including complex water surface profiles and hydraulic jumps. The results are compared with experimental and analytical data and the necessary values of under relaxation factors for a converged solution are discussed. No artificial viscosity was required, which is the advantage of the present model.