Wageeh El-Askary | Menoufiya University (original) (raw)
Papers by Wageeh El-Askary
Journal of Wind Engineering and Industrial Aerodynamics, 2017
Journal of Porous Media, 2020
The International Conference on Applied Mechanics and Mechanical Engineering, 2018
The present experimental work is devoted to explore the efficiency of alkaline water electrolysis... more The present experimental work is devoted to explore the efficiency of alkaline water electrolysis in producing hydrogen when it is operated by solar energy. The overall system efficiency is determined by measuring the solar irradiance as the source of the input energy, and the amount of hydrogen produced as the source of the output energy. Hence, the losses through the Photo-Voltaic (PV) cell, connecting wires, and the water electrolyzer, are all considered in the present study. Moreover, the effects of the gab width distance and the separators' types, on the overall system efficiency are also presented. It is found that, the higher the electrolyzer efficiency, the higher is the overall system efficiency at almost conditions. The significant reduction in system efficiency may be due to losses of the energy conversion through the PV cell and the electrical losses in the connecting wires. Though, the electrolyzer efficiency reaches 90% and the maximum overall system efficiency of 1.7% is barely achieved.
Applied Mechanics and Materials, 2012
This article presents a new, multi-foil-blades (multi-S) rotor and compare its performance potent... more This article presents a new, multi-foil-blades (multi-S) rotor and compare its performance potentials with traditional (Single-S) Savomius rotor . Theoretical and experimental investigations show that the performance of the multi-S rotor is better than the other classical designs of Savonius rotor in terms of the resulting power factor. Analytical equations for power and torque factors are developed for both the single- and multi-S rotors with ideal flow assumed. These equations are proven very effective in describing the performance potentials of these rotors for a range of speed ratio less than or equals 0.7. This result is experimentally justified for both types of rotors. For speed ratios higher than 0.7, a remarkable deviation occurs between the theoretical performance measures provided by the developed equations and the experimentally measured ones. A geometric design parameter which depends on the internal construction of the proposed multi-S rotor is found to be of great imp...
The International Conference on Mathematics and Engineering Physics, 2016
The effect of wall slip conditions, porous media and heat transfer on peristaltic flow of MHD New... more The effect of wall slip conditions, porous media and heat transfer on peristaltic flow of MHD Newtonian fluid in catheterized tube has been studied under the assumptions of longwavelength and low-Reynolds number. The analytical solution has been derived for velocity and temperature.The amplitude ratio (ϕ), particle concentration (C), catheter size (ε) and the dimensionless flow rate (Q)were used to obtain the pressure gradient.The results for velocity and temperature obtained in the analysis have been evaluated numerically and discussed.Thetube surface was maintained at a constant temperature.The variations of several parameters were discussed by using suitable graphs.The mathematical model was corresponding to the flow in the annular space of two concentric tubes.
Journal of Energy Resources Technology
In the current article, E216 airfoil blades with linearized chord of a small-scale horizontal axi... more In the current article, E216 airfoil blades with linearized chord of a small-scale horizontal axis wind turbine are numerically investigated to enhance the performance of the turbine. The blade is modified by including grooves on its suction side. Three-dimensional Reynold’s averaged Navier–Stokes (RANS) simulations are performed with Shear Stress Transport k–ω as a turbulence model. The computed power-coefficient results are first validated with previous measurements by the present authors on a wind turbine of 1 m rotor diameter at two wind speeds of 6 and 8 m/s. Another validation with measurements from the literature is performed via comparison of the pressure-coefficient distribution along surfaces of E216 airfoil at an angle of attack of 6 deg. Based on the successful computation, six different rotor models are numerically investigated with different numbers and locations of grooves created along the blade length, from the hub to the tip region, on the blade suction side. The l...
Computer Modeling in Engineering & Sciences, 2011
ABSTRACT In the present paper, the characteristics of compressible turbulent flow in a porous cha... more ABSTRACT In the present paper, the characteristics of compressible turbulent flow in a porous channels subjected to either symmetric or asymmetric mass injection are numerically predicted. A numerical computer-program including different turbulence models has been developed by the present authors to investigate the considered flow. The numerical method is based on the control volume approach to solve the governing Reynolds-Averaged Navier-Stokes (RANS) equations. Turbulence modeling plays a significant role here, in light of the complex flow generated, so several popular engineering turbulence models with good track records are evaluated, including five different turbulence models. Numerical results with available experimental data showed that the flow evolves significantly with the distance from the front wall such that different regimes of flow development can be observed. The comparison between these computational models with experimental data for the axial velocity profiles and turbulent stresses is performed. The best numerical results are obtained from the shear-stress transport kw model (SST kw) and v2 f turbulence models as well. Although the v2 f turbulence model generates fair results compared to the experimental ones, it needs little bit improvement to be reliable to treat this kind of complex flows. However, because of the high cost and long computation time required with using either the family of kw or v2 f as well as the Reynolds Stress Model (RSM), the family of ke turbulence model still produces the behavior of turbulent flow in such complex turbulence structure with lowest cost and fair results.
Cmes-computer Modeling in Engineering & Sciences, 2011
Cmes-computer Modeling in Engineering & Sciences, 2012
In the present paper, a numerical code has been developed with differ- ent turbulence models aimi... more In the present paper, a numerical code has been developed with differ- ent turbulence models aiming at simulating turbulent bubbly flows in vertical cir- cular pipes. The mass and momentum conservation equations are used to describe the motion of both phases (water/air). Because of the averaging process additional models are needed for the inter-phase momentum transfer and turbulence quantities for closure. The continuous phase (water) turbulence is represented using different turbulence models namely: two-equation k-e, extended k-e and shear-stress trans- port (SST) k-w turbulence models which contains additional term to account for the effect of the dispersed phase (air) on the continuous phase turbulence. The de- veloped code is based on the finite volume method with the mentioned different turbulence models. The Reynolds stresses of the dispersed phase are calculated by relating them to those of the continuous phase through a turbulence response function. The code has been teste...
International Conference on Aerospace Sciences and Aviation Technology, 2011
In the present work, a complete simulation of reactive flow in the combustion chamber of a rocket... more In the present work, a complete simulation of reactive flow in the combustion chamber of a rocket motor equipped with convergent-divergent nozzle has been introduced. The model describes the combustion process inside the combustion chamber considering a steady premixed reactant gas injected through side porous walls of the combustion chamber. The products flow through a convergent-divergent nozzle with adiabatic impermeable walls. The reactants are treated as two-dimensional, multi-components, turbulent compressible flow. The local properties of the mixture are calculated and updated during the solution process. At the boundary of the combustion chamber, a constant mass flux and predefined properties are considered. The proposed model employs the basic conservation equations of continuity, momentum and energy as well as the finite rate of reaction and species transport equations. Finite volume method is used to solve the basic nonlinear partial differential equations numerically. The details of the numerical scheme, structure of the used grids, numerical accuracy and stability are introduced. The effect of grid resolution as well as the validity of the results is included. The results showed fair agreement with other models in the literature; specially the reaction zone depth, temperature contours and species concentration along the entire space of the combustion chamber.
BioNanoScience, 2018
The impact of heat transfer on the magnetohydrodynamic peristaltically induced motion in a channe... more The impact of heat transfer on the magnetohydrodynamic peristaltically induced motion in a channel through porous medium has been investigated. The continuity, momentum, and energy equations have been utilized to represent the flow in a closed form. These non-linear governing equations are solved analytically by employing the perturbation method. The obtained expressions for streamlines, temperature, and heat transfer coefficient are presented through graphs for two dimensions with a small wave number. The variations of physical variables with the pertinent parameters have been presented and discussed. It has been found that the inclusion of fluid suspension brought about a decrease in the temperature distribution. The effect of magnetic field on the temperature of fluid has also been seen to depend upon the position and time.
Journal of Wind Engineering and Industrial Aerodynamics, 2017
In the present work, the wake behavior of wind turbines, operating under thermally-stratified atm... more In the present work, the wake behavior of wind turbines, operating under thermally-stratified atmospheric boundary layer (ABL), is numerically investigated. The steady state three dimensional Reynolds-Averaged Navier-Stokes (RANS) equations, combined with the actuator disk approach, are used in the simulation. The standard k-ε turbulence model as well as a modified one namely El Kasmi model are adopted. Two different methods are used and compared, for representing the atmospheric stratification flow conditions: In the first one (direct method), the energy equation is considered along with mass, momentum, and turbulence model equations. In the second one (indirect method), stratification is modeled by means of additional buoyancy production and dissipation terms. Such terms are added to the turbulent kinetic energy and dissipation rate equations, instead of solving the energy equation. The results obtained from both methods show a reasonable agreement with the experimental data available from the literature. Moreover, it is concluded that, there is no significant difference between the predicted results from both methods. Further, the effect of the atmospheric stability class on the wake deficit and the available wind power in the wake region has been also investigated using the indirect method. It has been found that, there is a significant influence of the different atmospheric conditions on the wake behavior. In particular, the wake region becomes smaller with the decreasing of atmospheric stability, and hence a higher wind power in the wake region is observed for unstable conditions.
Powder Technology, 2016
The effects of solid-particles on downward turbulent-air flow through a pipe with sudden expansio... more The effects of solid-particles on downward turbulent-air flow through a pipe with sudden expansion are simulated by Eulerian-Lagrangian approach. Reynolds averaged Navier Stokes equations associated with standard k-ε turbulence model are used. Source terms are included to represent the effects of fluid-particle interactions and particle-particle collisions assuming non-deformed spherical shape particles. A FORTRAN code is developed based on the finite volume discretization with hybrid scheme to simulate the problem. Based on comparisons with published experimental work, the present code introduces good results that encourage the authors to extend the theoretical work considering different parameters. The performance of sudden expansion in the form of loss coefficient is studied at different particle sizes, mass loading ratios and Reynolds numbers. In light of the computational results, the finest particles can improve the performance of the sudden expansion, while the size of separation bubble increases.
Springer Proceedings in Physics
... energy of 300 mJ per pulse is used for the light pulses with a period 10 µs and 8 µs at 40 m/... more ... energy of 300 mJ per pulse is used for the light pulses with a period 10 µs and 8 µs at 40 m/s and 60 m/s ... In [3] Oesterlund and Johans-son measured the friction velocity with laser oil interferometry in a flat plate boundary layer with zero pressure gradient and showed a change ...
Journal of Wind Engineering and Industrial Aerodynamics, 2015
In this work three methods of controlling the wind direction were aiming at improving the perform... more In this work three methods of controlling the wind direction were aiming at improving the performance of Savonius rotor. The idea behind the new designs was to harvest the incoming wind to generate a wind jet to the concave side of the advanced blade and prevent the convex side of return blade from coming upwind stream. The prevented wind was guided in different designs to impinge the concave side of the return blade and hence to eliminate the negative torque and increase the exerted positive torque. The study could be numerically introduced using commercial Fluent-software. The SST k-ω turbulence model was used to simulate the turbulence behavior. The results showed that the suggested designs improve the performance of Savonius rotor in view of the power coefficient and the operation range. One of them enhanced the performance to reach a power-coefficient peak of 0.52 with operation range of tip speed ratio λ r 2:2. However, the new designs generated large wakes behind the rotor that must be considered in the turbines farm arrangement.
International Journal for Numerical Methods in Fluids, 2011
The paper explores the possibilities that different turbulence closures offer, for in-depth analy... more The paper explores the possibilities that different turbulence closures offer, for in-depth analysis of a complex flow. The case under investigation is steady, turbulent flow in a pipe with sudden expansion without/with normal-to-wall injection through jets. This is a typical geometry where generation of turbulence energy takes place, due to sudden change in boundary conditions. This study is aimed at investigating the capability of a developed computational program by the present authors with three different turbulence models to calculate the mean flow variables. Three two-equation models are implemented, namely the standard linear k −ε model, the low Reynolds number k −ε model and the cubic nonlinear eddy viscosity (NLEV) k −ε model. The performance of the chosen turbulence models is investigated with regard to the available data in the literature including velocity profiles, turbulent kinetic energy and reattachment position in a pipe expansion. In order to further assess the reliability of the turbulence models, an experimental program was conducted by the present authors also at the fluid mechanics laboratory of Menoufiya University. Preliminary measurements, including the surface pressure along the two walls of the expansion pipe and the pressure drop without and with the presence of different arrangements of wall jets produced by symmetrical or asymmetrical fluid cross-flow injection, are introduced. The results of the present studies demonstrate the superiority of the cubic NLEV k −ε model in predicting the flow characteristics over the entire domain. The simple low Reynolds number k −ε model also gives good prediction, especially when the reattachment point is concerned. The evaluation of the reattachment point and the pressure-loss coefficient is numerically addressed in the paper using the cubic NLEV k −ε model. The results show that the injection location can control the performance of the pipe-expansion system. It is concluded that the introduction of flow injection can increase the energy loss in the pipe expansion. The near-field turbulence structure is also considered in the present study and it is noticed that the turbulence level is strongly affected by the cross-flow injection and the jet location.
The International Conference on Applied Mechanics and Mechanical Engineering, 2016
Experimental and numerical studies on emulsion (oil-in-water) flow in rectangular cross-sectional... more Experimental and numerical studies on emulsion (oil-in-water) flow in rectangular cross-sectional area S-shaped diffusers have been carried out. The effects of different parameters including area ratio, curvature ratio, turning angle, flow path, inflow Reynolds number, oil concentration and emulsion status (stable/unstable) on the static pressure distributions and energy loss coefficient are considered. The numerical study is carried out using ANSYS R-15.0 software Fluid Flow Fluent (FFF) 3D with different turbulence models. The comparisons between the numerical results and experimental data show good agreement. The results indicate that the S-diffuser energy-loss coefficient is affected by the geometrical parameters of S-diffuser, and the flow parameters. The energy-loss coefficient for the case of stable emulsion is found to be greater than that of the unstable emulsion flow. A general correlation of energy-loss coefficient including geometrical and flow parameters for the validated studied cases of S-diffusers is developed in this paper.
40th AIAA Aerospace Sciences Meeting & Exhibit, 2002
ERCOFTAC Series, 2001
The paper presents a large-eddy simulation of the flow over a sharp trailing edge. To minimize th... more The paper presents a large-eddy simulation of the flow over a sharp trailing edge. To minimize the computational effort inflow conditions for fully developed turbulent compressible boundary layers are derived. Furthermore, to predict trailing edge noise new acoustic perturbation equations are introduced. The LES findings and the acoustical results show good agreement with experimental and numerical data.
Journal of Wind Engineering and Industrial Aerodynamics, 2017
Journal of Porous Media, 2020
The International Conference on Applied Mechanics and Mechanical Engineering, 2018
The present experimental work is devoted to explore the efficiency of alkaline water electrolysis... more The present experimental work is devoted to explore the efficiency of alkaline water electrolysis in producing hydrogen when it is operated by solar energy. The overall system efficiency is determined by measuring the solar irradiance as the source of the input energy, and the amount of hydrogen produced as the source of the output energy. Hence, the losses through the Photo-Voltaic (PV) cell, connecting wires, and the water electrolyzer, are all considered in the present study. Moreover, the effects of the gab width distance and the separators' types, on the overall system efficiency are also presented. It is found that, the higher the electrolyzer efficiency, the higher is the overall system efficiency at almost conditions. The significant reduction in system efficiency may be due to losses of the energy conversion through the PV cell and the electrical losses in the connecting wires. Though, the electrolyzer efficiency reaches 90% and the maximum overall system efficiency of 1.7% is barely achieved.
Applied Mechanics and Materials, 2012
This article presents a new, multi-foil-blades (multi-S) rotor and compare its performance potent... more This article presents a new, multi-foil-blades (multi-S) rotor and compare its performance potentials with traditional (Single-S) Savomius rotor . Theoretical and experimental investigations show that the performance of the multi-S rotor is better than the other classical designs of Savonius rotor in terms of the resulting power factor. Analytical equations for power and torque factors are developed for both the single- and multi-S rotors with ideal flow assumed. These equations are proven very effective in describing the performance potentials of these rotors for a range of speed ratio less than or equals 0.7. This result is experimentally justified for both types of rotors. For speed ratios higher than 0.7, a remarkable deviation occurs between the theoretical performance measures provided by the developed equations and the experimentally measured ones. A geometric design parameter which depends on the internal construction of the proposed multi-S rotor is found to be of great imp...
The International Conference on Mathematics and Engineering Physics, 2016
The effect of wall slip conditions, porous media and heat transfer on peristaltic flow of MHD New... more The effect of wall slip conditions, porous media and heat transfer on peristaltic flow of MHD Newtonian fluid in catheterized tube has been studied under the assumptions of longwavelength and low-Reynolds number. The analytical solution has been derived for velocity and temperature.The amplitude ratio (ϕ), particle concentration (C), catheter size (ε) and the dimensionless flow rate (Q)were used to obtain the pressure gradient.The results for velocity and temperature obtained in the analysis have been evaluated numerically and discussed.Thetube surface was maintained at a constant temperature.The variations of several parameters were discussed by using suitable graphs.The mathematical model was corresponding to the flow in the annular space of two concentric tubes.
Journal of Energy Resources Technology
In the current article, E216 airfoil blades with linearized chord of a small-scale horizontal axi... more In the current article, E216 airfoil blades with linearized chord of a small-scale horizontal axis wind turbine are numerically investigated to enhance the performance of the turbine. The blade is modified by including grooves on its suction side. Three-dimensional Reynold’s averaged Navier–Stokes (RANS) simulations are performed with Shear Stress Transport k–ω as a turbulence model. The computed power-coefficient results are first validated with previous measurements by the present authors on a wind turbine of 1 m rotor diameter at two wind speeds of 6 and 8 m/s. Another validation with measurements from the literature is performed via comparison of the pressure-coefficient distribution along surfaces of E216 airfoil at an angle of attack of 6 deg. Based on the successful computation, six different rotor models are numerically investigated with different numbers and locations of grooves created along the blade length, from the hub to the tip region, on the blade suction side. The l...
Computer Modeling in Engineering & Sciences, 2011
ABSTRACT In the present paper, the characteristics of compressible turbulent flow in a porous cha... more ABSTRACT In the present paper, the characteristics of compressible turbulent flow in a porous channels subjected to either symmetric or asymmetric mass injection are numerically predicted. A numerical computer-program including different turbulence models has been developed by the present authors to investigate the considered flow. The numerical method is based on the control volume approach to solve the governing Reynolds-Averaged Navier-Stokes (RANS) equations. Turbulence modeling plays a significant role here, in light of the complex flow generated, so several popular engineering turbulence models with good track records are evaluated, including five different turbulence models. Numerical results with available experimental data showed that the flow evolves significantly with the distance from the front wall such that different regimes of flow development can be observed. The comparison between these computational models with experimental data for the axial velocity profiles and turbulent stresses is performed. The best numerical results are obtained from the shear-stress transport kw model (SST kw) and v2 f turbulence models as well. Although the v2 f turbulence model generates fair results compared to the experimental ones, it needs little bit improvement to be reliable to treat this kind of complex flows. However, because of the high cost and long computation time required with using either the family of kw or v2 f as well as the Reynolds Stress Model (RSM), the family of ke turbulence model still produces the behavior of turbulent flow in such complex turbulence structure with lowest cost and fair results.
Cmes-computer Modeling in Engineering & Sciences, 2011
Cmes-computer Modeling in Engineering & Sciences, 2012
In the present paper, a numerical code has been developed with differ- ent turbulence models aimi... more In the present paper, a numerical code has been developed with differ- ent turbulence models aiming at simulating turbulent bubbly flows in vertical cir- cular pipes. The mass and momentum conservation equations are used to describe the motion of both phases (water/air). Because of the averaging process additional models are needed for the inter-phase momentum transfer and turbulence quantities for closure. The continuous phase (water) turbulence is represented using different turbulence models namely: two-equation k-e, extended k-e and shear-stress trans- port (SST) k-w turbulence models which contains additional term to account for the effect of the dispersed phase (air) on the continuous phase turbulence. The de- veloped code is based on the finite volume method with the mentioned different turbulence models. The Reynolds stresses of the dispersed phase are calculated by relating them to those of the continuous phase through a turbulence response function. The code has been teste...
International Conference on Aerospace Sciences and Aviation Technology, 2011
In the present work, a complete simulation of reactive flow in the combustion chamber of a rocket... more In the present work, a complete simulation of reactive flow in the combustion chamber of a rocket motor equipped with convergent-divergent nozzle has been introduced. The model describes the combustion process inside the combustion chamber considering a steady premixed reactant gas injected through side porous walls of the combustion chamber. The products flow through a convergent-divergent nozzle with adiabatic impermeable walls. The reactants are treated as two-dimensional, multi-components, turbulent compressible flow. The local properties of the mixture are calculated and updated during the solution process. At the boundary of the combustion chamber, a constant mass flux and predefined properties are considered. The proposed model employs the basic conservation equations of continuity, momentum and energy as well as the finite rate of reaction and species transport equations. Finite volume method is used to solve the basic nonlinear partial differential equations numerically. The details of the numerical scheme, structure of the used grids, numerical accuracy and stability are introduced. The effect of grid resolution as well as the validity of the results is included. The results showed fair agreement with other models in the literature; specially the reaction zone depth, temperature contours and species concentration along the entire space of the combustion chamber.
BioNanoScience, 2018
The impact of heat transfer on the magnetohydrodynamic peristaltically induced motion in a channe... more The impact of heat transfer on the magnetohydrodynamic peristaltically induced motion in a channel through porous medium has been investigated. The continuity, momentum, and energy equations have been utilized to represent the flow in a closed form. These non-linear governing equations are solved analytically by employing the perturbation method. The obtained expressions for streamlines, temperature, and heat transfer coefficient are presented through graphs for two dimensions with a small wave number. The variations of physical variables with the pertinent parameters have been presented and discussed. It has been found that the inclusion of fluid suspension brought about a decrease in the temperature distribution. The effect of magnetic field on the temperature of fluid has also been seen to depend upon the position and time.
Journal of Wind Engineering and Industrial Aerodynamics, 2017
In the present work, the wake behavior of wind turbines, operating under thermally-stratified atm... more In the present work, the wake behavior of wind turbines, operating under thermally-stratified atmospheric boundary layer (ABL), is numerically investigated. The steady state three dimensional Reynolds-Averaged Navier-Stokes (RANS) equations, combined with the actuator disk approach, are used in the simulation. The standard k-ε turbulence model as well as a modified one namely El Kasmi model are adopted. Two different methods are used and compared, for representing the atmospheric stratification flow conditions: In the first one (direct method), the energy equation is considered along with mass, momentum, and turbulence model equations. In the second one (indirect method), stratification is modeled by means of additional buoyancy production and dissipation terms. Such terms are added to the turbulent kinetic energy and dissipation rate equations, instead of solving the energy equation. The results obtained from both methods show a reasonable agreement with the experimental data available from the literature. Moreover, it is concluded that, there is no significant difference between the predicted results from both methods. Further, the effect of the atmospheric stability class on the wake deficit and the available wind power in the wake region has been also investigated using the indirect method. It has been found that, there is a significant influence of the different atmospheric conditions on the wake behavior. In particular, the wake region becomes smaller with the decreasing of atmospheric stability, and hence a higher wind power in the wake region is observed for unstable conditions.
Powder Technology, 2016
The effects of solid-particles on downward turbulent-air flow through a pipe with sudden expansio... more The effects of solid-particles on downward turbulent-air flow through a pipe with sudden expansion are simulated by Eulerian-Lagrangian approach. Reynolds averaged Navier Stokes equations associated with standard k-ε turbulence model are used. Source terms are included to represent the effects of fluid-particle interactions and particle-particle collisions assuming non-deformed spherical shape particles. A FORTRAN code is developed based on the finite volume discretization with hybrid scheme to simulate the problem. Based on comparisons with published experimental work, the present code introduces good results that encourage the authors to extend the theoretical work considering different parameters. The performance of sudden expansion in the form of loss coefficient is studied at different particle sizes, mass loading ratios and Reynolds numbers. In light of the computational results, the finest particles can improve the performance of the sudden expansion, while the size of separation bubble increases.
Springer Proceedings in Physics
... energy of 300 mJ per pulse is used for the light pulses with a period 10 µs and 8 µs at 40 m/... more ... energy of 300 mJ per pulse is used for the light pulses with a period 10 µs and 8 µs at 40 m/s and 60 m/s ... In [3] Oesterlund and Johans-son measured the friction velocity with laser oil interferometry in a flat plate boundary layer with zero pressure gradient and showed a change ...
Journal of Wind Engineering and Industrial Aerodynamics, 2015
In this work three methods of controlling the wind direction were aiming at improving the perform... more In this work three methods of controlling the wind direction were aiming at improving the performance of Savonius rotor. The idea behind the new designs was to harvest the incoming wind to generate a wind jet to the concave side of the advanced blade and prevent the convex side of return blade from coming upwind stream. The prevented wind was guided in different designs to impinge the concave side of the return blade and hence to eliminate the negative torque and increase the exerted positive torque. The study could be numerically introduced using commercial Fluent-software. The SST k-ω turbulence model was used to simulate the turbulence behavior. The results showed that the suggested designs improve the performance of Savonius rotor in view of the power coefficient and the operation range. One of them enhanced the performance to reach a power-coefficient peak of 0.52 with operation range of tip speed ratio λ r 2:2. However, the new designs generated large wakes behind the rotor that must be considered in the turbines farm arrangement.
International Journal for Numerical Methods in Fluids, 2011
The paper explores the possibilities that different turbulence closures offer, for in-depth analy... more The paper explores the possibilities that different turbulence closures offer, for in-depth analysis of a complex flow. The case under investigation is steady, turbulent flow in a pipe with sudden expansion without/with normal-to-wall injection through jets. This is a typical geometry where generation of turbulence energy takes place, due to sudden change in boundary conditions. This study is aimed at investigating the capability of a developed computational program by the present authors with three different turbulence models to calculate the mean flow variables. Three two-equation models are implemented, namely the standard linear k −ε model, the low Reynolds number k −ε model and the cubic nonlinear eddy viscosity (NLEV) k −ε model. The performance of the chosen turbulence models is investigated with regard to the available data in the literature including velocity profiles, turbulent kinetic energy and reattachment position in a pipe expansion. In order to further assess the reliability of the turbulence models, an experimental program was conducted by the present authors also at the fluid mechanics laboratory of Menoufiya University. Preliminary measurements, including the surface pressure along the two walls of the expansion pipe and the pressure drop without and with the presence of different arrangements of wall jets produced by symmetrical or asymmetrical fluid cross-flow injection, are introduced. The results of the present studies demonstrate the superiority of the cubic NLEV k −ε model in predicting the flow characteristics over the entire domain. The simple low Reynolds number k −ε model also gives good prediction, especially when the reattachment point is concerned. The evaluation of the reattachment point and the pressure-loss coefficient is numerically addressed in the paper using the cubic NLEV k −ε model. The results show that the injection location can control the performance of the pipe-expansion system. It is concluded that the introduction of flow injection can increase the energy loss in the pipe expansion. The near-field turbulence structure is also considered in the present study and it is noticed that the turbulence level is strongly affected by the cross-flow injection and the jet location.
The International Conference on Applied Mechanics and Mechanical Engineering, 2016
Experimental and numerical studies on emulsion (oil-in-water) flow in rectangular cross-sectional... more Experimental and numerical studies on emulsion (oil-in-water) flow in rectangular cross-sectional area S-shaped diffusers have been carried out. The effects of different parameters including area ratio, curvature ratio, turning angle, flow path, inflow Reynolds number, oil concentration and emulsion status (stable/unstable) on the static pressure distributions and energy loss coefficient are considered. The numerical study is carried out using ANSYS R-15.0 software Fluid Flow Fluent (FFF) 3D with different turbulence models. The comparisons between the numerical results and experimental data show good agreement. The results indicate that the S-diffuser energy-loss coefficient is affected by the geometrical parameters of S-diffuser, and the flow parameters. The energy-loss coefficient for the case of stable emulsion is found to be greater than that of the unstable emulsion flow. A general correlation of energy-loss coefficient including geometrical and flow parameters for the validated studied cases of S-diffusers is developed in this paper.
40th AIAA Aerospace Sciences Meeting & Exhibit, 2002
ERCOFTAC Series, 2001
The paper presents a large-eddy simulation of the flow over a sharp trailing edge. To minimize th... more The paper presents a large-eddy simulation of the flow over a sharp trailing edge. To minimize the computational effort inflow conditions for fully developed turbulent compressible boundary layers are derived. Furthermore, to predict trailing edge noise new acoustic perturbation equations are introduced. The LES findings and the acoustical results show good agreement with experimental and numerical data.