Hamid Bashiri - Academia.edu (original) (raw)

Papers by Hamid Bashiri

Research paper thumbnail of Experimental and numerical simulation of bidirectional propagation of an air cavity

Journal of Hydraulic Research, 2019

This study numerically and experimentally investigates the transient flow associated with a so-ca... more This study numerically and experimentally investigates the transient flow associated with a so-called Benjamin bubble, but, in contrast to previous studies, the approach permits bidirectional flow. Two experiments investigated the bidirectional propagation of an air cavity in a square tank; these two events were also simulated using a three-dimensional numerical model. An exactly conservative semi-Lagrangian scheme was employed to solve both the advection term in the momentum equation and the advection equation of the volume of fluid function. The model was compared with previous one-dimensional Benjamin bubble experimental data and a one-dimensional Boussinesq model. For the one-dimensional Benjamin bubble experiments, the three-dimensional model showed good agreement with both published data and a one-dimensional non-hydrostatic model. After modelling the advance of a one-dimensional cavity, a bidirectional Benjamin bubble was simulated using the three-dimensional model. The numerical results are in reasonable agreement with observations of the free surface and pressurized regions and reasonably predict the shape of the air-water interface.

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Research paper thumbnail of Assessment of two-equation model for simulation of air pocket advancing into a rectangular duct

Journal of Hydraulic Research, 2019

This research aims to evaluate the influence of air on the water surface and pressure profiles in... more This research aims to evaluate the influence of air on the water surface and pressure profiles in two-phase (air–water) flow. In previous studies, the authors used the continuity and momentum equations for water in a one-dimensional finite volume model. In the present study, the authors additionally incorporate both the mass conservation and momentum equations for incompressible fluids as basic equations for the air portion. Momentum equations were integrated for the free surface and pressurized flow regions after interface observations made at each time step. To correct velocity and pressure in the pressurized portion, the authors used the highly simplified mark-and-cell method. A pressure drop equation is used at the interface of pressurized and free surface flows to deduce the pressure. The Harten total variation diminishing scheme was used to avoid numerical oscillations. The results were compared with experimental data and numerical simulations without considering the air effect.

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Research paper thumbnail of Prediction of Local Scour Depth Downstream of Sluice Gates Using Harmony Search Algorithm and Artificial Neural Networks

Using two coupled models, this study predicts the maximum local scour depth downstream of sluice ... more Using two coupled models, this study predicts the maximum local scour depth downstream of sluice gates. The models are an artificial neural network (ANN) coupled with the harmony search (HS) algorithm, and an ANN coupled with a generalized reduced gradient (GRG) method. The models are trained and tested using extensive observations obtained from the literature. The main parameters used to predict the scour are apron length, densimetric Froude number, tailwater depth, and median sediment size. In addition, multiple linear regression (MLR) is applied to express the relationship between independent and dependent variables. Results of the ANN model coupled with HS and with GRG and of the MLR are compared. The performance of ANN is more effective when coupled with the HS algorithm. To increase the ability of the HS algorithm, a parameter varying method is applied. Results lead to the conclusion that ANN coupled with the HS algorithm is an accurate and simple method for predicting the maximum scour depth downstream of sluice gates.

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Research paper thumbnail of Valuation of flexibility for optimal reservoir operation

Open Water Journal, 2017

This research presents a valuation study of flexibility in hydropower generation. Flexibility her... more This research presents a valuation study of flexibility in hydropower generation. Flexibility herein is considered as a stochastic process and is defined as the difference between the maximum hydropower energy generation capacity and the scheduled energy production plan to meet the demand and obligatory sales of electricity. To value the flexibility , this framework combines options theory and the Non-dominated Sorting Genetic Algorithm II (NSGA-II), while this paper focuses only on real option model. Options theory is used in this research to create a framework that can value the flexibility at various levels of risk for a multi-reservoir system. A Black-Scholes-like equation, which is a Partial Differential Equation (PDE), is solved numerically using standard solvers. The value of flexibility is estimated based on the solution of the Black-Scholes-type model. The results could help in assessing the value of flexibility over time and hence, guide allocating hydropower generation capacity from one period to another.

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Research paper thumbnail of Quantification of Short-term Hydropower Generation Flexibility

Open Water Journal, 2017

The main goal of the current research is to quantify hydropower generation flexibility in a syste... more The main goal of the current research is to quantify hydropower generation flexibility in a system of ten multi-objective reservoirs on the Federal Columbia River Power System (FCRPS). At a given time step, the flexibility in electricity supply (F(t)) is defined as the remaining capacity after satisfying the scheduled production plan. The scheduled production plan includes the sum of future electricity demand and existing obligatory electricity sales resulting from open market sales of electricity. The time-varying flexibility metric is expressed in energy units (MWh). Estimating the flexibility helps the energy producers to address potential negative shocks in energy supply (e.g., due to shocks in wind/solar energy or increased regulatory constraints). To quantify the flexibility, we use a hydraulic routing model to simulate the maximum capacity in energy production at any given time period, given the initial (e.g., current) forebay elevation level in the reservoirs and conditioning on the operational and regulatory constraints. The maximum hydropower generation capacity depends on the given inflows. In this study, we defined the maximum and minimum flexibility, and tested the proposed framework on a ten reservoir system on the Columbia River in the Pacific North-West in the USA.

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Research paper thumbnail of Propagation of an Air-Water Interface from Pressurized to Free-Surface Flow in a Circular Pipe

Journal of Hydraulic Engineering, ASCE, 2016

Hydraulic transients with the movement of an interface between pressurized flow and free surface ... more Hydraulic transients with the movement of an interface between pressurized flow and free surface flow can be observed in rapid water emptying in the pipes. This study focuses on air cavity intrusion into horizontal and inclined circular pipes. Laboratory experiments were carried out to observe the negative surge during depressurization in a circular pipe. In order to generate the undular bore in a circular pipe, in some cases a sharp-crested weir at the open end of the horizontal pipe was used. Various behaviors of air cavity were observed for a series of weir heights. A numerical model is proposed and applied to the cavity flow in a circular pipe. To reproduce the undular bore in circular pipes (when water depth is greater than pipe radius), this study derived the depth-averaged shallow water equations with the effects of vertical acceleration using the Boussinesq equation. In this study, the continuity and the momentum equations of free surface and pressurized flows with the hydrostatic and the Boussinesq pressure assumptions have been used. The results from the model showed good agreement with the experimental results.

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Research paper thumbnail of Experimental and Numerical Analysis of Air Cavity Intrusion in a Horizontal Circular Pipe

Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 2015

ABSTRACT This paper presents an experimental and numerical study of transient flow from pressuriz... more ABSTRACT This paper presents an experimental and numerical study of transient flow from pressurized flow to open channel free surface flow in a horizontal circular pipe. A one-dimensional (1D) depth-averaged velocity model is developed to study the unsteady flow in mixed pressurized-free surface flow, which can be occur due to the rapid movement of a gate. The numerical approach is an interface tracking and after finding the interface position, the pressure drop is considered at the interface. To evaluate the numerical model performance, some experiments were conducted in a straight circular pipe using water and air as two fluids. In order to generate the undular bore, in some cases a weir was used at the open end of the pipe. The results of the comparisons lead to the conclusion that the pressure drop at the interface is very important. Results also showed that in the case of free overfall, the hydrostatic and Bouussinesq models can reproduce air cavity front shape with a reasonably good agreement with experiments.

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Research paper thumbnail of Simulation of Air Cavity Advancing into a Straight Duct

Two fundamental one-dimensional (1D) models are proposed and applied to simulate the transient fl... more Two fundamental one-dimensional (1D) models are proposed and applied to simulate the transient flows with the propagation of an interface in a water-filled duct. The proposed models are developed to simulate the unsteady open channel flows based on finite-volume method (FVM). The models presented herein are based on the continuity and momentum equations of free surface and pressurized flows and the momentum equation of an interface between both flows. However, the highly simplified marker and cell (HSMAC) method with pressure iteration procedures is applied to the pressurized flow region. The numerical simulations are performed under the hydraulic conditions of previous experiments, and then simulated results were compared with the experimental data. It is pointed out that the solitary wave solution is able to reproduce the air cavity profile. In contrast to the hydrostatic model, results of the Boussinesq model compare reasonably well to the experimental observations.

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Research paper thumbnail of The motion of entrapped air cavities in inclined ducts

The paper reports a study of the water surface profile of an entrapped air cavity while emptying ... more The paper reports a study of the water surface profile of an entrapped air cavity while emptying water in an initially filled inclined duct. A one-dimensional (1D) model, which consists of the continuity and momentum equations applicable for open channel flow, pipe flow and air–water interface flow, is developed based on the finite volume method. A pressure drop model is proposed to reproduce a better profile around the cavity front, with a particular focus on air pressure changes inside the confined cavity to simulate a kind of transient flow with an entrapped air cavity. In contrast to the previous studies, the application of the model shows that when the pressure drop is not considered and the air pressure is not changed, the confined cavity soon vanishes. A comparison between the simulated and experimental results shows that the model is able to accurately reproduce the water surface profile of an entrapped air cavity while emptying inclined ducts.

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Research paper thumbnail of Application of Harmony Search Algorithm to Reservoir Operation Optimization

In this study, a meta-heuristic technique called harmony search (HS) algorithm is developed for r... more In this study, a meta-heuristic technique called harmony search (HS) algorithm is developed for reservoir operation optimization with respect to flood control. The HS algorithm is used to minimize the water supply deficit and flood damages downstream of a reservoir. The GIS database is used to determine the flood damage functions. The efficacy of HS algorithm is evaluated in comparison with other techniques by using a benchmark problem for a single reservoir operation optimization problem. HS showed promising results in terms of speed of convergence to an optimal objective function value compared with other techniques such as honey-bee mating optimization (HBMO) and a global optimization model (LINGO 8.0 NLP solver). The HS algorithm is then applied to the Narmab reservoir, north of Iran, as a case study. Narmab reservoir serves multiple purposes including irrigation, flood control, and drinking water requirements. The developed model is applied for monthly operation. The results show that the HS algorithm can be effectively used for operation of reservoir for flood management.

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Research paper thumbnail of Experimental and numerical simulation of bidirectional propagation of an air cavity

Journal of Hydraulic Research, 2019

This study numerically and experimentally investigates the transient flow associated with a so-ca... more This study numerically and experimentally investigates the transient flow associated with a so-called Benjamin bubble, but, in contrast to previous studies, the approach permits bidirectional flow. Two experiments investigated the bidirectional propagation of an air cavity in a square tank; these two events were also simulated using a three-dimensional numerical model. An exactly conservative semi-Lagrangian scheme was employed to solve both the advection term in the momentum equation and the advection equation of the volume of fluid function. The model was compared with previous one-dimensional Benjamin bubble experimental data and a one-dimensional Boussinesq model. For the one-dimensional Benjamin bubble experiments, the three-dimensional model showed good agreement with both published data and a one-dimensional non-hydrostatic model. After modelling the advance of a one-dimensional cavity, a bidirectional Benjamin bubble was simulated using the three-dimensional model. The numerical results are in reasonable agreement with observations of the free surface and pressurized regions and reasonably predict the shape of the air-water interface.

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Research paper thumbnail of Assessment of two-equation model for simulation of air pocket advancing into a rectangular duct

Journal of Hydraulic Research, 2019

This research aims to evaluate the influence of air on the water surface and pressure profiles in... more This research aims to evaluate the influence of air on the water surface and pressure profiles in two-phase (air–water) flow. In previous studies, the authors used the continuity and momentum equations for water in a one-dimensional finite volume model. In the present study, the authors additionally incorporate both the mass conservation and momentum equations for incompressible fluids as basic equations for the air portion. Momentum equations were integrated for the free surface and pressurized flow regions after interface observations made at each time step. To correct velocity and pressure in the pressurized portion, the authors used the highly simplified mark-and-cell method. A pressure drop equation is used at the interface of pressurized and free surface flows to deduce the pressure. The Harten total variation diminishing scheme was used to avoid numerical oscillations. The results were compared with experimental data and numerical simulations without considering the air effect.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Prediction of Local Scour Depth Downstream of Sluice Gates Using Harmony Search Algorithm and Artificial Neural Networks

Using two coupled models, this study predicts the maximum local scour depth downstream of sluice ... more Using two coupled models, this study predicts the maximum local scour depth downstream of sluice gates. The models are an artificial neural network (ANN) coupled with the harmony search (HS) algorithm, and an ANN coupled with a generalized reduced gradient (GRG) method. The models are trained and tested using extensive observations obtained from the literature. The main parameters used to predict the scour are apron length, densimetric Froude number, tailwater depth, and median sediment size. In addition, multiple linear regression (MLR) is applied to express the relationship between independent and dependent variables. Results of the ANN model coupled with HS and with GRG and of the MLR are compared. The performance of ANN is more effective when coupled with the HS algorithm. To increase the ability of the HS algorithm, a parameter varying method is applied. Results lead to the conclusion that ANN coupled with the HS algorithm is an accurate and simple method for predicting the maximum scour depth downstream of sluice gates.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Valuation of flexibility for optimal reservoir operation

Open Water Journal, 2017

This research presents a valuation study of flexibility in hydropower generation. Flexibility her... more This research presents a valuation study of flexibility in hydropower generation. Flexibility herein is considered as a stochastic process and is defined as the difference between the maximum hydropower energy generation capacity and the scheduled energy production plan to meet the demand and obligatory sales of electricity. To value the flexibility , this framework combines options theory and the Non-dominated Sorting Genetic Algorithm II (NSGA-II), while this paper focuses only on real option model. Options theory is used in this research to create a framework that can value the flexibility at various levels of risk for a multi-reservoir system. A Black-Scholes-like equation, which is a Partial Differential Equation (PDE), is solved numerically using standard solvers. The value of flexibility is estimated based on the solution of the Black-Scholes-type model. The results could help in assessing the value of flexibility over time and hence, guide allocating hydropower generation capacity from one period to another.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Quantification of Short-term Hydropower Generation Flexibility

Open Water Journal, 2017

The main goal of the current research is to quantify hydropower generation flexibility in a syste... more The main goal of the current research is to quantify hydropower generation flexibility in a system of ten multi-objective reservoirs on the Federal Columbia River Power System (FCRPS). At a given time step, the flexibility in electricity supply (F(t)) is defined as the remaining capacity after satisfying the scheduled production plan. The scheduled production plan includes the sum of future electricity demand and existing obligatory electricity sales resulting from open market sales of electricity. The time-varying flexibility metric is expressed in energy units (MWh). Estimating the flexibility helps the energy producers to address potential negative shocks in energy supply (e.g., due to shocks in wind/solar energy or increased regulatory constraints). To quantify the flexibility, we use a hydraulic routing model to simulate the maximum capacity in energy production at any given time period, given the initial (e.g., current) forebay elevation level in the reservoirs and conditioning on the operational and regulatory constraints. The maximum hydropower generation capacity depends on the given inflows. In this study, we defined the maximum and minimum flexibility, and tested the proposed framework on a ten reservoir system on the Columbia River in the Pacific North-West in the USA.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Propagation of an Air-Water Interface from Pressurized to Free-Surface Flow in a Circular Pipe

Journal of Hydraulic Engineering, ASCE, 2016

Hydraulic transients with the movement of an interface between pressurized flow and free surface ... more Hydraulic transients with the movement of an interface between pressurized flow and free surface flow can be observed in rapid water emptying in the pipes. This study focuses on air cavity intrusion into horizontal and inclined circular pipes. Laboratory experiments were carried out to observe the negative surge during depressurization in a circular pipe. In order to generate the undular bore in a circular pipe, in some cases a sharp-crested weir at the open end of the horizontal pipe was used. Various behaviors of air cavity were observed for a series of weir heights. A numerical model is proposed and applied to the cavity flow in a circular pipe. To reproduce the undular bore in circular pipes (when water depth is greater than pipe radius), this study derived the depth-averaged shallow water equations with the effects of vertical acceleration using the Boussinesq equation. In this study, the continuity and the momentum equations of free surface and pressurized flows with the hydrostatic and the Boussinesq pressure assumptions have been used. The results from the model showed good agreement with the experimental results.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Experimental and Numerical Analysis of Air Cavity Intrusion in a Horizontal Circular Pipe

Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 2015

ABSTRACT This paper presents an experimental and numerical study of transient flow from pressuriz... more ABSTRACT This paper presents an experimental and numerical study of transient flow from pressurized flow to open channel free surface flow in a horizontal circular pipe. A one-dimensional (1D) depth-averaged velocity model is developed to study the unsteady flow in mixed pressurized-free surface flow, which can be occur due to the rapid movement of a gate. The numerical approach is an interface tracking and after finding the interface position, the pressure drop is considered at the interface. To evaluate the numerical model performance, some experiments were conducted in a straight circular pipe using water and air as two fluids. In order to generate the undular bore, in some cases a weir was used at the open end of the pipe. The results of the comparisons lead to the conclusion that the pressure drop at the interface is very important. Results also showed that in the case of free overfall, the hydrostatic and Bouussinesq models can reproduce air cavity front shape with a reasonably good agreement with experiments.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Simulation of Air Cavity Advancing into a Straight Duct

Two fundamental one-dimensional (1D) models are proposed and applied to simulate the transient fl... more Two fundamental one-dimensional (1D) models are proposed and applied to simulate the transient flows with the propagation of an interface in a water-filled duct. The proposed models are developed to simulate the unsteady open channel flows based on finite-volume method (FVM). The models presented herein are based on the continuity and momentum equations of free surface and pressurized flows and the momentum equation of an interface between both flows. However, the highly simplified marker and cell (HSMAC) method with pressure iteration procedures is applied to the pressurized flow region. The numerical simulations are performed under the hydraulic conditions of previous experiments, and then simulated results were compared with the experimental data. It is pointed out that the solitary wave solution is able to reproduce the air cavity profile. In contrast to the hydrostatic model, results of the Boussinesq model compare reasonably well to the experimental observations.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The motion of entrapped air cavities in inclined ducts

The paper reports a study of the water surface profile of an entrapped air cavity while emptying ... more The paper reports a study of the water surface profile of an entrapped air cavity while emptying water in an initially filled inclined duct. A one-dimensional (1D) model, which consists of the continuity and momentum equations applicable for open channel flow, pipe flow and air–water interface flow, is developed based on the finite volume method. A pressure drop model is proposed to reproduce a better profile around the cavity front, with a particular focus on air pressure changes inside the confined cavity to simulate a kind of transient flow with an entrapped air cavity. In contrast to the previous studies, the application of the model shows that when the pressure drop is not considered and the air pressure is not changed, the confined cavity soon vanishes. A comparison between the simulated and experimental results shows that the model is able to accurately reproduce the water surface profile of an entrapped air cavity while emptying inclined ducts.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Application of Harmony Search Algorithm to Reservoir Operation Optimization

In this study, a meta-heuristic technique called harmony search (HS) algorithm is developed for r... more In this study, a meta-heuristic technique called harmony search (HS) algorithm is developed for reservoir operation optimization with respect to flood control. The HS algorithm is used to minimize the water supply deficit and flood damages downstream of a reservoir. The GIS database is used to determine the flood damage functions. The efficacy of HS algorithm is evaluated in comparison with other techniques by using a benchmark problem for a single reservoir operation optimization problem. HS showed promising results in terms of speed of convergence to an optimal objective function value compared with other techniques such as honey-bee mating optimization (HBMO) and a global optimization model (LINGO 8.0 NLP solver). The HS algorithm is then applied to the Narmab reservoir, north of Iran, as a case study. Narmab reservoir serves multiple purposes including irrigation, flood control, and drinking water requirements. The developed model is applied for monthly operation. The results show that the HS algorithm can be effectively used for operation of reservoir for flood management.

Bookmarks Related papers MentionsView impact