Ismail Sakr - Academia.edu (original) (raw)
Papers by Ismail Sakr
ERJ. Engineering Research Journal
ERJ. Engineering Research Journal
This investigation aims to analyze experimentally and numerically the performance of the Savonius... more This investigation aims to analyze experimentally and numerically the performance of the Savonius wind turbine with a modified blade shape/profile. The wind turbine rotor introduced consists of two hook-shaped buckets connected by a Batch/arm with different bucket orientations. Blades of the cross-section with different thicknesses are considered. The simulations are carried out using the three-dimensional incompressible unsteady Reynolds-Average Navier Stokes (RANS) equations along with the RNG k-ε turbulence model. The results indicate that the RNG k-ε turbulence model achieves a good prediction of the rotor performance, in comparison with the literature and the current measurements. Six rotor models are investigated to explore the effect of rotor shape along with blade thickness on the wind turbine performance. It is revealed that the rotor model with a blade thickness of 2 mm and bucket orientation with a parallel armbucket, Model 4, has the best performance among the tested rotors. The static torque shows positive values for all rotor angles with a maximum static torque coefficient of 0.45, which reveals the high starting ability of the present rotor.
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 (SSHAWT) are numerically investigated to enhance the performance of the turbine. The blade is modified by including grooves on its suction side. Three-dimensional RANS simulations are performed with Shear Stress Transport (SST) 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°. 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 lift and drag coefficien...
International Journal of Medicine in Developing Countries, 2018
Background: A wide use of light-activated resin composites, in clinics, has increased recently du... more Background: A wide use of light-activated resin composites, in clinics, has increased recently due to the increased needs for esthetics teeth fillings. This in vitro study evaluated the wear resistance of various direct resin composites with different compositions. Methodology: Composite samples were divided into three main groups: group A representing 20 discs of Filtek Z350 XT, group B representing 20 discs of Bio active restorative and group C (as antagonist composite) representing 40 discs of Filtek Z250 XT. A programmable logic controlled equipment was used to record the two body wear of tested composites. Images analysis software evaluated the tested samples surface topography. Statistical analysis was performed using studentÂ’s t-test and Aasistat 7.6 statistics software. Results: It was found that group B composite recorded statistically significant higher weight loss mean value; and in antagonistic composite groups, non-significant higher weight loss mean value than group A composite mean value. Also, it was found that group B composite recorded statistically non-significant higher roughness change mean value than group A composite mean value. It was found that group A antagonistic composite recorded statistically non-significant higher roughness change mean value. Conclusion: A different wear resistance is observed for the two-body wear test, combining the results confirmed that the use of nanoparticles filled resin composites of value reduces abrasion of opposing surface especially with hard fillers like zirconia. A higher filler load in excess of 60 (vol %) results in increasing wear resistance although that softer glass particles filler was used.
ERJ. Engineering Research Journal
The world nowadays is looking for a clean source of renewable energy that produces no air or wate... more The world nowadays is looking for a clean source of renewable energy that produces no air or water pollution. Wind energy has become an optimal solution for world needs and the governments offer great attention to wind-energy development. In the present work, two outstanding Savonius rotor models are first investigated numerically using the three-dimensional unsteady Reynolds-averaged Navier-Stokes (URANS) equations, along with the Shear Stress Transport (SST) k-ω turbulence model. Various twist angles are trained for both rotor models and the best efficient model is further fabricated and tested experimentally using an open jet wind tunnel. The numerical and experimental results show good agreement, and the proposed rotor geometry has superior performance. The maximum power coefficient obtained for that optimum rotor is found to be 0.221 at the highest performance twist angle of 45 o. Furthermore, the proposed rotor model introduces a positive torque coefficient during the entire rotation cycle, with reduced cyclic torque.
Journal of Energy Resources Technology, 2020
In this paper, measurements and computations are performed to study the performance of a 45-deg t... more In this paper, measurements and computations are performed to study the performance of a 45-deg twisted Savonius rotor with a modified profile, at various overlap ratios (δ), aspect ratios (AR), and wind velocity (V). A free air jet test rig is used to carry out the experiments, while three-dimensional unsteady Reynolds-averaged Navier–Stokes (URANS) equations are used, in conjunction with the renormalization group (RNG) k–ɛ turbulence model, to perform the computations. The present experimental results successfully verify the simulation predictions obtained by the selected turbulence model. The RNG k–ɛ turbulence model has been chosen based on previous tests performed and published by the authors. Furthermore, both torque coefficient (CT) and power coefficient (CP) are numerically predicted at various tip speed ratios (λ) for overlap ratios (δ) ranging from 0.0 to 0.5, aspect ratios (AR) ranging from 0.75 to 3, and wind velocity values ranging from 4 to 18 m/s. Unlike the conventio...
Journal of Energy Resources Technology, 2020
This article aims to study numerically the effect of curvature of linear blade profile on the per... more This article aims to study numerically the effect of curvature of linear blade profile on the performance of small-scale horizontal axis wind turbine (SSHAWT). Rotors with two curvature types, f forward angles 5 deg, 10 deg, 15 deg, 20 deg, 30 deg, and 45 deg and backward angles −5 deg, −10 deg, and −15 deg, are investigated. Furthermore, three curvature positions of r/R = 0.8, 0.9, and 0.95 are studied. The numerical simulations are performed on rotors of radius 0.5 m at different wind speeds. The results are compared with straight rotor of linear profiles of chord and twist, which is considered as base rotor. It is found that the rotor with forward curvature of 5 deg and r/R = 0.9 has the highest power coefficient compared with the other rotors. At the peak performance, the proposed rotor reduces the axial thrust by about 12.5% compared with the base rotor. The flow behavior represented by the streamlines contours is also discussed. In such case, the separation approximately disap...
The comprehensive analysis of the fluid flow and heat transfer patterns inside the buoyancy-drive... more The comprehensive analysis of the fluid flow and heat transfer patterns inside the buoyancy-driven square cavities is a necessary precursor to the evolution of better designs for more complex industrial applications. In the present paper, a focused study on the problem of the buoyancy-driven cavity with different working mediums and a wide range of thermal properties is presented. The adopted numerical method is based on the solution of the complete Navier-Stokes and energy equations using the finite volume technique employing SIMPLE algorithm on a staggered grid. The buoyancy forces are represented using the Boussinesq approximation. The present scheme is used to generate benchmark-quality data for the entire laminar and transient natural-convection-Rayleigh number range of 103 ≤Ra ≤109 for different working mediums having a wide rang of Prandtl number (0.71, 10.0, 210.5 and 11648.57). Consequently, an elaborate analysis of the heat transfer process in such cavities is obtained. A ...
Arabian Journal for Science and Engineering, 2014
This paper investigates theoretically and experimentally the optimum operating conditions for alk... more This paper investigates theoretically and experimentally the optimum operating conditions for alkaline water electrolysis coupled with a solar photovoltaic (PV) source for hydrogen generation with emphasis on the electrolyzer efficiency under different operating conditions. The PV generator is simulated using Matlab/Simulink to obtain its characteristics under different operating conditions with solar irradiance and temperature variations. A wide range of operating parameters, which include input voltage, temperature, concentration of the electrolyte, and distance between the electrodes, are considered, and their effects on the efficiency of hydrogen production process are explored. A group of performance curves for the solar-hydrogen energy system (SHES) under a wide range of operating conditions are obtained through a number of individual experimental measurements. The optimum operating conditions, which correspond to the maximum electrolyzer efficiency, are determined for the proposed SHES. The effects of the ambient temperature and the electrolyte temperature on the performance of the solar PV energy system and the hydrogen production process are also investigated.
Chip encapsulation on printed circuit boards (PCB) requires an accurate amount of encapsulation m... more Chip encapsulation on printed circuit boards (PCB) requires an accurate amount of encapsulation material to protect the chip in semiconductor packaging. Encapsulationmaterials are usually made of epoxy but sometimes other materials are used, like silicones.The study of convective flows and heat transfers in such systems of immiscible liquid layershas a great potential. In the current investigation, the failure criteria of the encapsulated chipssubjected to high level of differential heating is numerically defined. The Reynolds-AveragedNavier-Stokes equations along with energy equation are solved on the basis of the controlvolume approach. The level set formulation is applied to smooth the discontinuous propertiesof the encapsulated layers and to predict the dynamics of the separation surface between thetwo layers. The numerical results obtained showed that most of the failure occurs in encapsulated chips and semiconductors are referred to the deformation of the separation surface es...
The International Conference on Applied Mechanics and Mechanical Engineering
Thermocapillary flows within a differentially heated rectangular cavity containing two immiscible... more Thermocapillary flows within a differentially heated rectangular cavity containing two immiscible liquid layers are of considerable technological importance in materials processing applications particularly under microgravity conditions where the influence of buoyancy-driven convection is minimized. In the present study, for the first time, we account the affect of normal and tangential forces that control the track of the moving interface by using level set method (LSM). A 2-D numerical procedure for two immiscible fluid systems on the basis of a single phase model and the level set formulation is developed. The time dependent Navier-Stokes and energy equations are solved by means of the control volume approach on a staggered rectangular grid system. The numerical model interprets the tangential and the normal stresses by a single-phase model using a heavy side function. The topological change of the interface between the two immiscible flows is described by the level set method. According to our background this is the first study of such cases using the single phase model and the control volume formulation. Two cases have been studied: the first case contains a system with only one liquid interface (melt/encapsulant) between the two immiscible fluids. The second one has a system with encapsulant free surface opened to air (and so, subjected to a second thermocapillary forces). Both the liquid-liquid interface and the free surface are assumed to be initially flat, which is a valid assumption according to earlier theoretical and experimental results. In later cases, the liquid-liquid interface is allowed to deform. The numerical results are compared with the available analytical models and experimental results. The comparisons showed an acceptable agreement between the present predicted results and the available data shown in the available references.
ERJ. Engineering Research Journal
Due to the urgent need for electricity sources in Egypt, this investigation is an attempt to prep... more Due to the urgent need for electricity sources in Egypt, this investigation is an attempt to prepare a metering tool for measuring the flow rate of the suspended gas-solid mixture flows in coal thermal power stations. One of the simplest methods for accurately measuring the flow rate of pulverized coal in the thermal power stations is the venturi meter. In the present work, different geometrical models have been designed and applied for measuring air-coal mixture flow rate, considering the effect of different operational parameters on the pressure sensitivity, pressure recovery and performance of the venturi models. The measurements showed the effects of these parameters on the pressure drop and the pressure distribution. New charts have been deduced from the experimental data for seven non-standard venturi models that shows different effects of particle size, loading ratio and throat length of venturi. From the experimental results a new correlation for two-phase flow discharge coefficient is deduced in the present study. The comparison between the experimental and correlation has been done with error percentage from +25% to-20%.
ERJ. Engineering Research Journal
ERJ. Engineering Research Journal
This investigation aims to analyze experimentally and numerically the performance of the Savonius... more This investigation aims to analyze experimentally and numerically the performance of the Savonius wind turbine with a modified blade shape/profile. The wind turbine rotor introduced consists of two hook-shaped buckets connected by a Batch/arm with different bucket orientations. Blades of the cross-section with different thicknesses are considered. The simulations are carried out using the three-dimensional incompressible unsteady Reynolds-Average Navier Stokes (RANS) equations along with the RNG k-ε turbulence model. The results indicate that the RNG k-ε turbulence model achieves a good prediction of the rotor performance, in comparison with the literature and the current measurements. Six rotor models are investigated to explore the effect of rotor shape along with blade thickness on the wind turbine performance. It is revealed that the rotor model with a blade thickness of 2 mm and bucket orientation with a parallel armbucket, Model 4, has the best performance among the tested rotors. The static torque shows positive values for all rotor angles with a maximum static torque coefficient of 0.45, which reveals the high starting ability of the present rotor.
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 (SSHAWT) are numerically investigated to enhance the performance of the turbine. The blade is modified by including grooves on its suction side. Three-dimensional RANS simulations are performed with Shear Stress Transport (SST) 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°. 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 lift and drag coefficien...
International Journal of Medicine in Developing Countries, 2018
Background: A wide use of light-activated resin composites, in clinics, has increased recently du... more Background: A wide use of light-activated resin composites, in clinics, has increased recently due to the increased needs for esthetics teeth fillings. This in vitro study evaluated the wear resistance of various direct resin composites with different compositions. Methodology: Composite samples were divided into three main groups: group A representing 20 discs of Filtek Z350 XT, group B representing 20 discs of Bio active restorative and group C (as antagonist composite) representing 40 discs of Filtek Z250 XT. A programmable logic controlled equipment was used to record the two body wear of tested composites. Images analysis software evaluated the tested samples surface topography. Statistical analysis was performed using studentÂ’s t-test and Aasistat 7.6 statistics software. Results: It was found that group B composite recorded statistically significant higher weight loss mean value; and in antagonistic composite groups, non-significant higher weight loss mean value than group A composite mean value. Also, it was found that group B composite recorded statistically non-significant higher roughness change mean value than group A composite mean value. It was found that group A antagonistic composite recorded statistically non-significant higher roughness change mean value. Conclusion: A different wear resistance is observed for the two-body wear test, combining the results confirmed that the use of nanoparticles filled resin composites of value reduces abrasion of opposing surface especially with hard fillers like zirconia. A higher filler load in excess of 60 (vol %) results in increasing wear resistance although that softer glass particles filler was used.
ERJ. Engineering Research Journal
The world nowadays is looking for a clean source of renewable energy that produces no air or wate... more The world nowadays is looking for a clean source of renewable energy that produces no air or water pollution. Wind energy has become an optimal solution for world needs and the governments offer great attention to wind-energy development. In the present work, two outstanding Savonius rotor models are first investigated numerically using the three-dimensional unsteady Reynolds-averaged Navier-Stokes (URANS) equations, along with the Shear Stress Transport (SST) k-ω turbulence model. Various twist angles are trained for both rotor models and the best efficient model is further fabricated and tested experimentally using an open jet wind tunnel. The numerical and experimental results show good agreement, and the proposed rotor geometry has superior performance. The maximum power coefficient obtained for that optimum rotor is found to be 0.221 at the highest performance twist angle of 45 o. Furthermore, the proposed rotor model introduces a positive torque coefficient during the entire rotation cycle, with reduced cyclic torque.
Journal of Energy Resources Technology, 2020
In this paper, measurements and computations are performed to study the performance of a 45-deg t... more In this paper, measurements and computations are performed to study the performance of a 45-deg twisted Savonius rotor with a modified profile, at various overlap ratios (δ), aspect ratios (AR), and wind velocity (V). A free air jet test rig is used to carry out the experiments, while three-dimensional unsteady Reynolds-averaged Navier–Stokes (URANS) equations are used, in conjunction with the renormalization group (RNG) k–ɛ turbulence model, to perform the computations. The present experimental results successfully verify the simulation predictions obtained by the selected turbulence model. The RNG k–ɛ turbulence model has been chosen based on previous tests performed and published by the authors. Furthermore, both torque coefficient (CT) and power coefficient (CP) are numerically predicted at various tip speed ratios (λ) for overlap ratios (δ) ranging from 0.0 to 0.5, aspect ratios (AR) ranging from 0.75 to 3, and wind velocity values ranging from 4 to 18 m/s. Unlike the conventio...
Journal of Energy Resources Technology, 2020
This article aims to study numerically the effect of curvature of linear blade profile on the per... more This article aims to study numerically the effect of curvature of linear blade profile on the performance of small-scale horizontal axis wind turbine (SSHAWT). Rotors with two curvature types, f forward angles 5 deg, 10 deg, 15 deg, 20 deg, 30 deg, and 45 deg and backward angles −5 deg, −10 deg, and −15 deg, are investigated. Furthermore, three curvature positions of r/R = 0.8, 0.9, and 0.95 are studied. The numerical simulations are performed on rotors of radius 0.5 m at different wind speeds. The results are compared with straight rotor of linear profiles of chord and twist, which is considered as base rotor. It is found that the rotor with forward curvature of 5 deg and r/R = 0.9 has the highest power coefficient compared with the other rotors. At the peak performance, the proposed rotor reduces the axial thrust by about 12.5% compared with the base rotor. The flow behavior represented by the streamlines contours is also discussed. In such case, the separation approximately disap...
The comprehensive analysis of the fluid flow and heat transfer patterns inside the buoyancy-drive... more The comprehensive analysis of the fluid flow and heat transfer patterns inside the buoyancy-driven square cavities is a necessary precursor to the evolution of better designs for more complex industrial applications. In the present paper, a focused study on the problem of the buoyancy-driven cavity with different working mediums and a wide range of thermal properties is presented. The adopted numerical method is based on the solution of the complete Navier-Stokes and energy equations using the finite volume technique employing SIMPLE algorithm on a staggered grid. The buoyancy forces are represented using the Boussinesq approximation. The present scheme is used to generate benchmark-quality data for the entire laminar and transient natural-convection-Rayleigh number range of 103 ≤Ra ≤109 for different working mediums having a wide rang of Prandtl number (0.71, 10.0, 210.5 and 11648.57). Consequently, an elaborate analysis of the heat transfer process in such cavities is obtained. A ...
Arabian Journal for Science and Engineering, 2014
This paper investigates theoretically and experimentally the optimum operating conditions for alk... more This paper investigates theoretically and experimentally the optimum operating conditions for alkaline water electrolysis coupled with a solar photovoltaic (PV) source for hydrogen generation with emphasis on the electrolyzer efficiency under different operating conditions. The PV generator is simulated using Matlab/Simulink to obtain its characteristics under different operating conditions with solar irradiance and temperature variations. A wide range of operating parameters, which include input voltage, temperature, concentration of the electrolyte, and distance between the electrodes, are considered, and their effects on the efficiency of hydrogen production process are explored. A group of performance curves for the solar-hydrogen energy system (SHES) under a wide range of operating conditions are obtained through a number of individual experimental measurements. The optimum operating conditions, which correspond to the maximum electrolyzer efficiency, are determined for the proposed SHES. The effects of the ambient temperature and the electrolyte temperature on the performance of the solar PV energy system and the hydrogen production process are also investigated.
Chip encapsulation on printed circuit boards (PCB) requires an accurate amount of encapsulation m... more Chip encapsulation on printed circuit boards (PCB) requires an accurate amount of encapsulation material to protect the chip in semiconductor packaging. Encapsulationmaterials are usually made of epoxy but sometimes other materials are used, like silicones.The study of convective flows and heat transfers in such systems of immiscible liquid layershas a great potential. In the current investigation, the failure criteria of the encapsulated chipssubjected to high level of differential heating is numerically defined. The Reynolds-AveragedNavier-Stokes equations along with energy equation are solved on the basis of the controlvolume approach. The level set formulation is applied to smooth the discontinuous propertiesof the encapsulated layers and to predict the dynamics of the separation surface between thetwo layers. The numerical results obtained showed that most of the failure occurs in encapsulated chips and semiconductors are referred to the deformation of the separation surface es...
The International Conference on Applied Mechanics and Mechanical Engineering
Thermocapillary flows within a differentially heated rectangular cavity containing two immiscible... more Thermocapillary flows within a differentially heated rectangular cavity containing two immiscible liquid layers are of considerable technological importance in materials processing applications particularly under microgravity conditions where the influence of buoyancy-driven convection is minimized. In the present study, for the first time, we account the affect of normal and tangential forces that control the track of the moving interface by using level set method (LSM). A 2-D numerical procedure for two immiscible fluid systems on the basis of a single phase model and the level set formulation is developed. The time dependent Navier-Stokes and energy equations are solved by means of the control volume approach on a staggered rectangular grid system. The numerical model interprets the tangential and the normal stresses by a single-phase model using a heavy side function. The topological change of the interface between the two immiscible flows is described by the level set method. According to our background this is the first study of such cases using the single phase model and the control volume formulation. Two cases have been studied: the first case contains a system with only one liquid interface (melt/encapsulant) between the two immiscible fluids. The second one has a system with encapsulant free surface opened to air (and so, subjected to a second thermocapillary forces). Both the liquid-liquid interface and the free surface are assumed to be initially flat, which is a valid assumption according to earlier theoretical and experimental results. In later cases, the liquid-liquid interface is allowed to deform. The numerical results are compared with the available analytical models and experimental results. The comparisons showed an acceptable agreement between the present predicted results and the available data shown in the available references.
ERJ. Engineering Research Journal
Due to the urgent need for electricity sources in Egypt, this investigation is an attempt to prep... more Due to the urgent need for electricity sources in Egypt, this investigation is an attempt to prepare a metering tool for measuring the flow rate of the suspended gas-solid mixture flows in coal thermal power stations. One of the simplest methods for accurately measuring the flow rate of pulverized coal in the thermal power stations is the venturi meter. In the present work, different geometrical models have been designed and applied for measuring air-coal mixture flow rate, considering the effect of different operational parameters on the pressure sensitivity, pressure recovery and performance of the venturi models. The measurements showed the effects of these parameters on the pressure drop and the pressure distribution. New charts have been deduced from the experimental data for seven non-standard venturi models that shows different effects of particle size, loading ratio and throat length of venturi. From the experimental results a new correlation for two-phase flow discharge coefficient is deduced in the present study. The comparison between the experimental and correlation has been done with error percentage from +25% to-20%.