AHMAD SHARAFI | Air University of Science and Technology (original) (raw)

Papers by AHMAD SHARAFI

Amirkabir University of Technology, Aug 5, 2019

Iranian Aerospace Society, Mar 21, 2021

In the present study, the aerodynamic performance of the ducted fan is investigated using the sur... more In the present study, the aerodynamic performance of the ducted fan is investigated using the surface vorticity method and the lifting line theory. In previous research, to consider the effects of the duct, most of the parameters derived from empirical tests or computational fluid dynamics. Our goal is to present a new method for considering the effects of the duct on the fan enclosed in a duct. In this method, the lift and drag coefficients are only input parameters. The present method requires considerably less computational time than CFD methods. Also, the aerodynamic optimization of fan blades geometry has been carried out using particle swarm optimization method (PSO) to achieve the optimum blade geometry and the maximum output power. The results of this method are in excellent agreement with experimental data in references. By optimizing the geometry of the blade, the output power of ducted fan increased 10 percentage in comparison to ducted fan with old blade geometry

An extensive experimental investigation is conducted to study the effect of canard position UHODW... more An extensive experimental investigation is conducted to study the effect of canard position UHODWLYHHWRRWKHHIXVHODJHHUHIHUHQFHHOLQHHRQQWKHHDHURG\QDPLFFIRUFHVVRIIDD¿JKWHUUW\SHHFRQ¿JX-UDWLRQQPRGHO$HURG\QDPLFFIRUFHVVDWWGLIIHUHQWWÀLJKWWFRQGLWLRQVVDUHHPHDVXUHGGLQQDDVXEVRQLFF wind tunnel. The wing and the canard have triquetrous shapes. Experiments are conducted DWW5H\QROGVVQXPEHUURIIDQGGDWWWRRGHJUHHHDQJOHVVRIIDWWDFN7KHHUHVXOWVVVKRZZWKDWW FDQDUGGLQFUHDVHVVWKHHOLIWWDQGGGUDJJIRUFHVVZKLOHHLWWGHFUHDVHVVWKHHVWDWLFFVWDELOLW\\RIIWKHHPRGHO The canard at its up position

[1] Rocket propulsion elements [2] Liquid injection thrust vector control and effective parameter... more [1] Rocket propulsion elements [2] Liquid injection thrust vector control and effective parameters [3] An experimental investigation of thrust vector control by secondary injection [4] Analysis of performance of hot gas injection thrust vector control system [5] Comparison of Euler and navier-stokes solutions for nozzle flows with secondary injection [6] Jet tab thrust vector control [7] Jet tab thrust vector control system demonstration [8] The flow generated by ramp tabs in a rocket nozzle exhaust [9] Effects of vortex generating tabs on noise sources in an ideally expanded Mach 1.3 jet [10] Corrugated tabs for supersonic jet control [11] A computational study of thrust vectoring control using dual throat nozzle [12] Thrust shock vector control of an axisymmetric conical supersonic nozzle via secondary transverse gas injection [13] Numerical simulation of fluidic thrust vectoring in an axisymmetric supersonic nozzle [14] Large eddy simulation of shock vector control using bypass flow passage [15] CFD modeling for flow field characterization and performance analysis of HGITVC [16] Experimental and simulation testing of thermal loading in the jet tabs of a thrust vector control system [17] experimental investigation of the effect of cylindrical protuberance with different penetration the thrust vector a c-d nozzle in supersonic regime [18] Turbulent jet in crossflow analysis with LES approach [19] New visions in experimental investigations of a supersonic under-expanded jet into a high subsonic crossflow [20] Detailed flow physics of the supersonic jet interaction flow field In this research, the effect of several unconventional obstructions with cubic, spherical, cylindrical, and cone geometries on the propulsion vector of a convergent-divergent micro nozzle as a new method in propulsion vector control is experimentally investigated. For this purpose, a convergent-divergent nozzle was designed and constructed in small dimensions. This nozzle is such that the Mach number is its nominal output in full expansion conditions 2. The wall of this nozzle is designed to measure pressure variations with pressure holes. Also, in the nozzle wall, a duct has been created to apply a bulge inside the nozzle. Pressure sensors and the shadograph system have been used to pressure measurement and check the outlet flow field respectively. The total pressure of the calming chamber is constant in all experiments and is equal to 5.5 times. The results of this study show that the maximum deviation is related to an obstruction with a cubic geometry which is 2.1 degrees. Also, the geometries that have sharp corners are more shock-shaped and hit the opposite wall. In this research, the shock formed by a cubic barrier has hit the opposite wall, but with a spherical shaped and cone-shaped barrier, the shock comes out from the nozzle. Also, these results indicate that the axial force of the nozzle has been reduced to a very small extent.

In this research, a low speed wind tunnel test has been carried out to investigate the effects of... more In this research, a low speed wind tunnel test has been carried out to investigate the effects of adding grid winglet, its size and number of fingers on the flow pattern over the upper surface of a wing model and its aerodynamic coefficients. The investigation has been performed for different angles of attack ranging from -2 to 21 degrees and at a free stream velocity of 24.7 m/sec, corresponding to the Reynolds number of 101000. The model has a rectangular shape with an aspect ratio of 4.75. Wing section airfoil is NACA 23016. Flow visualization is performed using tuft over the upper surface of the wing and lift & drag coefficients are measured. The obtained results show that at low angles of attack (lower than 6 degree), adding the grid winglet has no effect on the lift & drag coefficients. However, at higher angles of attack, its effect increases. Maximum amount of lift and minimum amount of drag is for the case that the grid winglet has 4 fingers sorted from long to short.

Annals of Nutrition and Metabolism, 2008

SHARIF: MECHANICAL …, 2009

A series of experiments are conducted to study the velocity field around a wing-canard body that ... more A series of experiments are conducted to study the velocity field around a wing-canard body that represents a highly maneuverable aircraft. All experiments were conducted in a subsonic wind tunnel under two different angles of attack, Jmodel= 15, 20 degrees, while ...

JOURNAL OF AERONAUTICAL ENGINEERING …, 2010

In this research, low speed wind tunnel tests have been carried out to investigate the canard con... more In this research, low speed wind tunnel tests have been carried out to investigate the canard configuration and location on the pressure distribution over a maneuverable aircraft model. The applied wing and canard are delta shape with a sharp leading-edge. The ...

In this research, canard and its vertical and longitudinal positions effects on pressure distribu... more In this research, canard and its vertical and longitudinal positions effects on pressure distribution and aerodynamic coefficients of a maneuverable aircraft wing model have been investigated numerically applying the fluent software. The investigations have been performed at the Reynolds number of 5×10 and different angles of attack, using unstructured grid and the Reynolds stress modeling. The applied wing and canard are delta shape and the supposed canard longitudinal positions are front, middle and rear, and its vertical positions are up, middle and low, respect to the main delta wing. For the case of no canard configuration model, the obtained results show that until angle of attack of 25 degrees, there is a very good agreement between the experimental data and the numerical results. Adding the canard causes the vortex on the wing upper surface become stronger and bigger. Also, for all longitudinal and vertical positions of the canard, the canard’s wake passes over the main wing...

Journal of Aeronautical Engineering, 2020

In this research, the design, fabrication, and aerodynamic analysis of a small remote-controlled ... more In this research, the design, fabrication, and aerodynamic analysis of a small remote-controlled airship are investigated. The airship must be capable of carrying a 2kg payload. In this research, the design of various parts of an airship such as envelope, gondola and tail has been investigated by using theoretical and empirical formulas. To check the accuracy of the design, digital datcom software was used to perform
an analytical analysis as well as the fluent software to numerically evaluate the flow around the airship and calculate the forces and moments applied to it. The investigations were carried out at a free stream speed 15m / s and in the various angles of attack from -10 ° to 10 °. In the numerical study with fluent software, the unstructured grid and the k -w SST turbulence model were used. The results showed that the airship was well modeled in digital Datcom software. Also, at low angles of attack, the good agreement between fluent's data and digital Datcom's data is observed. Digital Datcom's data can be used to obtain aerodynamic coefficients during the design phase. At all angles of attack, the airship has static stability and at low angles of attack, it has the least stability and maximum maneuverability. The drag coefficient obtained from Digital Datcom has a significant difference with the Fluent and other references data. therefore, Digital Datcom cannot be predicted at design phases for the drag coefficient.

journal of Aerospace Science and Technology, 2021

In the present study, the aerodynamic performance of the ducted fan is investigated using the sur... more In the present study, the aerodynamic performance of the ducted fan is investigated using the surface vorticity method and the lifting line theory. In previous research, to consider the effects of the duct, most of the parameters derived from empirical tests or computational fluid dynamics. Our goal is to present a new method for considering the effects of the duct on the fan enclosed in a duct. In this method, the lift and drag coefficients are only input parameters. The present method requires considerably less computational time than CFD methods. Also, the aerodynamic optimization of fan blades geometry has been carried out using particle swarm optimization method (PSO) to achieve the optimum blade geometry and the maximum output power. The results of this method are in excellent agreement with experimental data in references. By optimizing the geometry of the blade, the output power of ducted fan increased 10 percentage in comparison to ducted fan with old blade geometry

In this research, canard and its vertical and longitudinal positions effects on pressure distribu... more In this research, canard and its vertical and longitudinal positions effects on pressure distribution and aerodynamic coefficients of a maneuverable aircraft wing model have been investigated numerically applying the fluent software. The investigations have been performed at the Reynolds number of 5×105 and different angles of attack, using unstructured grid and the Reynolds stress modeling. The applied wing and canard are delta shape and the supposed canard longitudinal positions are front, middle and rear, and its vertical positions are up, middle and low, respect to the main delta wing. For the case of no canard configuration model, the obtained results show that until angle of attack of 25 degrees, there is a very good agreement between the experimental data and the numerical results. Adding the canard causes the vortex on the wing upper surface become stronger and bigger. Also, for all longitudinal and vertical positions of the canard, the canard’s wake passes over the main win...

In this study, the behavior of a subject consisting of a cylinder with 4 plates perpendicular to ... more In this study, the behavior of a subject consisting of a cylinder with 4 plates perpendicular to it with a rotational degree of freedom under airflow both through the numerical approach, known as improved discrete vortex and experimental approach were investigated. The experimental and numerical results have shown that oscillating regime occurs in low velocity and length. This movement is vibrations with irregular range around an equilibrium angle of 45 degree. In oscillating motion regime, it is seen that after releasing the object in free flow, a high torque force, due to the flow’s acceleration from the model, is induced to the plates and makes a big angular change, but after a while, the range of oscillation around the equilibrium angle of 45 degree decreases. The probability of rotational motion regime in length ratio of one and velocity of 13 m/sec in initial angle of attack is low. However, the experimental and numerical results have indicated that still in high initial angle...

Amirkabir Journal of Mechanical Engineering, 2019

In this study, the effect of steady spanwise blowing on the aerodynamic coefficients of a maneuve... more In this study, the effect of steady spanwise blowing on the aerodynamic coefficients of a maneuverable aircraft wing model have been simulated three dimensionally applying the fluent software. The simulations have been performed at the Mach number of 0.4 and different angles of attack, using unstructured grid and the k-w SSTturbulence model. Numerical simulation results showed that the spanwise blowing along the wing leading edge caused a flow along the axis of leading edge vortex and delayed the vortex breakdown until the high angles of attack. As a result, the lift coefficient increases at higher angles of attack, which is directly related to the jet momentum coefficient. By applying blowing, due to the vortex breakdown on the wing surface, drag coefficient is greater in comparison to the no blowing condition until the angle of attack 24 degree and after this angle, the drag coefficient decreases. Also, drag coefficient decrease is lower at greater jet momentum coefficients. By injecting the flow over the wing, the vortex increases in different longitudinal sections and causes
a greater pressure drop on the upper surface of the wing. Also, the greatest amount of pressure in the inner span of the wing and near the edge of the wing attack is observed.

Modares Mechanical Engineering, 2020

[1] Rocket propulsion elements [2] Liquid injection thrust vector control and effective parameter... more [1] Rocket propulsion elements [2] Liquid injection thrust vector control and effective parameters [3] An experimental investigation of thrust vector control by secondary injection [4] Analysis of performance of hot gas injection thrust vector control system [5] Comparison of Euler and navier-stokes solutions for nozzle flows with secondary injection [6] Jet tab thrust vector control [7] Jet tab thrust vector control system demonstration [8] The flow generated by ramp tabs in a rocket nozzle exhaust [9] Effects of vortex generating tabs on noise sources in an ideally expanded Mach 1.3 jet [10] Corrugated tabs for supersonic jet control [11] A computational study of thrust vectoring control using dual throat nozzle [12] Thrust shock vector control of an axisymmetric conical supersonic nozzle via secondary transverse gas injection [13] Numerical simulation of fluidic thrust vectoring in an axisymmetric supersonic nozzle [14] Large eddy simulation of shock vector control using bypass flow passage [15] CFD modeling for flow field characterization and performance analysis of HGITVC [16] Experimental and simulation testing of thermal loading in the jet tabs of a thrust vector control system [17] experimental investigation of the effect of cylindrical protuberance with different penetration the thrust vector a c-d nozzle in supersonic regime [18] Turbulent jet in crossflow analysis with LES approach [19] New visions in experimental investigations of a supersonic under-expanded jet into a high subsonic crossflow [20] Detailed flow physics of the supersonic jet interaction flow field In this research, the effect of several unconventional obstructions with cubic, spherical, cylindrical, and cone geometries on the propulsion vector of a convergent-divergent micro nozzle as a new method in propulsion vector control is experimentally investigated. For this purpose, a convergent-divergent nozzle was designed and constructed in small dimensions. This nozzle is such that the Mach number is its nominal output in full expansion conditions 2. The wall of this nozzle is designed to measure pressure variations with pressure holes. Also, in the nozzle wall, a duct has been created to apply a bulge inside the nozzle. Pressure sensors and the shadograph system have been used to pressure measurement and check the outlet flow field respectively. The total pressure of the calming chamber is constant in all experiments and is equal to 5.5 times. The results of this study show that the maximum deviation is related to an obstruction with a cubic geometry which is 2.1 degrees. Also, the geometries that have sharp corners are more shock-shaped and hit the opposite wall. In this research, the shock formed by a cubic barrier has hit the opposite wall, but with a spherical shaped and cone-shaped barrier, the shock comes out from the nozzle. Also, these results indicate that the axial force of the nozzle has been reduced to a very small extent.

JOURNAL OF SOLID AND FLUID MECHANIC, 2017

In this research, canard and its vertical and longitudinal positions effects on pressure distribu... more In this research, canard and its vertical and longitudinal positions effects on pressure distribution and aerodynamic coefficients of a maneuverable aircraft wing model have been investigated numerically applying the fluent software. The investigations have been performed at the Reynolds number of 5×10 5 and different angles of attack, using unstructured grid and the Reynolds stress modeling. The applied wing and canard are delta shape and the supposed canard longitudinal positions are front, middle and rear, and its vertical positions are up, middle and low, respect to the main delta wing. For the case of no canard configuration model, the obtained results show that until angle of attack of 25 degrees, there is a very good agreement between the experimental data and the numerical results. Adding the canard causes the vortex on the wing upper surface become stronger and bigger. Also, for all longitudinal and vertical positions of the canard, the canard's wake passes over the main wing surface. When the canard is at forward-up position respect to the main wing, the highest amount of lift force achieves. Furthermore, the least amount of drag force relates to the case which the canard is closer to the main wing and along with its axis. However, maximum amount of aerodynamic performance achieves when canard is at down-forward position respect to the main delta wing.

Journal of Aeronautical Engineering, 2018

In this research, the experimental investigation of unsteady flow around a cylinder model with th... more In this research, the experimental investigation of unsteady flow around a cylinder model with three plates perpendicular to it has been discussed. This study has been done at different speeds, primary model angle of attacks and length ratios. The results show that the model has steady and unsteady oscillation and rotational motions. These types of behaviors depend on the plate's length ratio, primary object angle of attack, and free stream velocity. The model has damping motion around an angle of 60 degree, at low speed and length ratio. The greatest oscillational or rotational flow has appeared at initial angle of attack of 0 degree. In low length ratio, the regime of motion is oscillations that it changed to rotational motion when the length ratio and free stream velocity increase. The variation of angular velocity at length ratio of 1 and 4, with respect to time, are accompanied with reduction of vibrations range per motion. Also, over time, the vibrational velocity of the model is reduced. In addition, the results show that by increasing the Reynolds Number, Strouhal number becomes constant.

In this research, canard and its vertical and longitudinal positions effects on pressure distribu... more In this research, canard and its vertical and longitudinal positions effects on pressure distribution and aerodynamic coefficients of a maneuverable aircraft wing model have been investigated numerically applying the fluent software. The investigations have been performed at the Reynolds number of 5×105 and different angles of attack, using unstructured grid and the Reynolds stress modeling. The applied wing and canard are delta shape and the supposed canard longitudinal positions are front, middle and rear, and its vertical positions are up, middle and low, respect to the main delta wing. For the case of no canard configuration model, the obtained results show that until angle of attack of 25 degrees, there is a very good agreement between the experimental data and the numerical results. Adding the canard causes the vortex on the wing upper surface become stronger and bigger. Also, for all longitudinal and vertical positions of the canard, the canard’s wake passes over the main wing surface. When the canard is at forward-up position respect to the main wing, the highest amount of lift force achieves. Furthermore, the least amount of drag force relates to the case which the canard is closer to the main wing and along with its axis. However, maximum amount of aerodynamic performance achieves when canard is at down-forward position respect to the main delta wing.

A series of experiments are conducted to study the velocity field around a wing- canard body that... more A series of experiments are conducted to study the velocity field around a wing- canard body that represents a highly maneuverable aircraft. All experiments were conducted in a subsonic wind tunnel under two different angle of attack, α_model=15,20 degrees, while the canard angle of attack varied between -10 to 10 degrees. The data shows that, at all the angles of attack mentioned before, the canard downwash passes over the main wing surface, which results in a reduction of the pressure over the wing surface. These phenomena delay the model stall angle of attack, hence, increasing the performance of the model. Furthermore, to reduce the experiments, a neural network system was used, which is capable of both prediction and extrapolation. The neural network data shows both canard and main wing vortices at various stations over the wing surface. As the canard angle stronger and cover a layer portion of the wing surface. As a result of this vortex system, the pressure over the wing surface drops considerably.

Amirkabir University of Technology, Aug 5, 2019

Iranian Aerospace Society, Mar 21, 2021

In the present study, the aerodynamic performance of the ducted fan is investigated using the sur... more In the present study, the aerodynamic performance of the ducted fan is investigated using the surface vorticity method and the lifting line theory. In previous research, to consider the effects of the duct, most of the parameters derived from empirical tests or computational fluid dynamics. Our goal is to present a new method for considering the effects of the duct on the fan enclosed in a duct. In this method, the lift and drag coefficients are only input parameters. The present method requires considerably less computational time than CFD methods. Also, the aerodynamic optimization of fan blades geometry has been carried out using particle swarm optimization method (PSO) to achieve the optimum blade geometry and the maximum output power. The results of this method are in excellent agreement with experimental data in references. By optimizing the geometry of the blade, the output power of ducted fan increased 10 percentage in comparison to ducted fan with old blade geometry

An extensive experimental investigation is conducted to study the effect of canard position UHODW... more An extensive experimental investigation is conducted to study the effect of canard position UHODWLYHHWRRWKHHIXVHODJHHUHIHUHQFHHOLQHHRQQWKHHDHURG\QDPLFFIRUFHVVRIIDD¿JKWHUUW\SHHFRQ¿JX-UDWLRQQPRGHO$HURG\QDPLFFIRUFHVVDWWGLIIHUHQWWÀLJKWWFRQGLWLRQVVDUHHPHDVXUHGGLQQDDVXEVRQLFF wind tunnel. The wing and the canard have triquetrous shapes. Experiments are conducted DWW5H\QROGVVQXPEHUURIIDQGGDWWWRRGHJUHHHDQJOHVVRIIDWWDFN7KHHUHVXOWVVVKRZZWKDWW FDQDUGGLQFUHDVHVVWKHHOLIWWDQGGGUDJJIRUFHVVZKLOHHLWWGHFUHDVHVVWKHHVWDWLFFVWDELOLW\\RIIWKHHPRGHO The canard at its up position

[1] Rocket propulsion elements [2] Liquid injection thrust vector control and effective parameter... more [1] Rocket propulsion elements [2] Liquid injection thrust vector control and effective parameters [3] An experimental investigation of thrust vector control by secondary injection [4] Analysis of performance of hot gas injection thrust vector control system [5] Comparison of Euler and navier-stokes solutions for nozzle flows with secondary injection [6] Jet tab thrust vector control [7] Jet tab thrust vector control system demonstration [8] The flow generated by ramp tabs in a rocket nozzle exhaust [9] Effects of vortex generating tabs on noise sources in an ideally expanded Mach 1.3 jet [10] Corrugated tabs for supersonic jet control [11] A computational study of thrust vectoring control using dual throat nozzle [12] Thrust shock vector control of an axisymmetric conical supersonic nozzle via secondary transverse gas injection [13] Numerical simulation of fluidic thrust vectoring in an axisymmetric supersonic nozzle [14] Large eddy simulation of shock vector control using bypass flow passage [15] CFD modeling for flow field characterization and performance analysis of HGITVC [16] Experimental and simulation testing of thermal loading in the jet tabs of a thrust vector control system [17] experimental investigation of the effect of cylindrical protuberance with different penetration the thrust vector a c-d nozzle in supersonic regime [18] Turbulent jet in crossflow analysis with LES approach [19] New visions in experimental investigations of a supersonic under-expanded jet into a high subsonic crossflow [20] Detailed flow physics of the supersonic jet interaction flow field In this research, the effect of several unconventional obstructions with cubic, spherical, cylindrical, and cone geometries on the propulsion vector of a convergent-divergent micro nozzle as a new method in propulsion vector control is experimentally investigated. For this purpose, a convergent-divergent nozzle was designed and constructed in small dimensions. This nozzle is such that the Mach number is its nominal output in full expansion conditions 2. The wall of this nozzle is designed to measure pressure variations with pressure holes. Also, in the nozzle wall, a duct has been created to apply a bulge inside the nozzle. Pressure sensors and the shadograph system have been used to pressure measurement and check the outlet flow field respectively. The total pressure of the calming chamber is constant in all experiments and is equal to 5.5 times. The results of this study show that the maximum deviation is related to an obstruction with a cubic geometry which is 2.1 degrees. Also, the geometries that have sharp corners are more shock-shaped and hit the opposite wall. In this research, the shock formed by a cubic barrier has hit the opposite wall, but with a spherical shaped and cone-shaped barrier, the shock comes out from the nozzle. Also, these results indicate that the axial force of the nozzle has been reduced to a very small extent.

In this research, a low speed wind tunnel test has been carried out to investigate the effects of... more In this research, a low speed wind tunnel test has been carried out to investigate the effects of adding grid winglet, its size and number of fingers on the flow pattern over the upper surface of a wing model and its aerodynamic coefficients. The investigation has been performed for different angles of attack ranging from -2 to 21 degrees and at a free stream velocity of 24.7 m/sec, corresponding to the Reynolds number of 101000. The model has a rectangular shape with an aspect ratio of 4.75. Wing section airfoil is NACA 23016. Flow visualization is performed using tuft over the upper surface of the wing and lift & drag coefficients are measured. The obtained results show that at low angles of attack (lower than 6 degree), adding the grid winglet has no effect on the lift & drag coefficients. However, at higher angles of attack, its effect increases. Maximum amount of lift and minimum amount of drag is for the case that the grid winglet has 4 fingers sorted from long to short.

Annals of Nutrition and Metabolism, 2008

SHARIF: MECHANICAL …, 2009

A series of experiments are conducted to study the velocity field around a wing-canard body that ... more A series of experiments are conducted to study the velocity field around a wing-canard body that represents a highly maneuverable aircraft. All experiments were conducted in a subsonic wind tunnel under two different angles of attack, Jmodel= 15, 20 degrees, while ...

JOURNAL OF AERONAUTICAL ENGINEERING …, 2010

In this research, low speed wind tunnel tests have been carried out to investigate the canard con... more In this research, low speed wind tunnel tests have been carried out to investigate the canard configuration and location on the pressure distribution over a maneuverable aircraft model. The applied wing and canard are delta shape with a sharp leading-edge. The ...

In this research, canard and its vertical and longitudinal positions effects on pressure distribu... more In this research, canard and its vertical and longitudinal positions effects on pressure distribution and aerodynamic coefficients of a maneuverable aircraft wing model have been investigated numerically applying the fluent software. The investigations have been performed at the Reynolds number of 5×10 and different angles of attack, using unstructured grid and the Reynolds stress modeling. The applied wing and canard are delta shape and the supposed canard longitudinal positions are front, middle and rear, and its vertical positions are up, middle and low, respect to the main delta wing. For the case of no canard configuration model, the obtained results show that until angle of attack of 25 degrees, there is a very good agreement between the experimental data and the numerical results. Adding the canard causes the vortex on the wing upper surface become stronger and bigger. Also, for all longitudinal and vertical positions of the canard, the canard’s wake passes over the main wing...

Journal of Aeronautical Engineering, 2020

In this research, the design, fabrication, and aerodynamic analysis of a small remote-controlled ... more In this research, the design, fabrication, and aerodynamic analysis of a small remote-controlled airship are investigated. The airship must be capable of carrying a 2kg payload. In this research, the design of various parts of an airship such as envelope, gondola and tail has been investigated by using theoretical and empirical formulas. To check the accuracy of the design, digital datcom software was used to perform
an analytical analysis as well as the fluent software to numerically evaluate the flow around the airship and calculate the forces and moments applied to it. The investigations were carried out at a free stream speed 15m / s and in the various angles of attack from -10 ° to 10 °. In the numerical study with fluent software, the unstructured grid and the k -w SST turbulence model were used. The results showed that the airship was well modeled in digital Datcom software. Also, at low angles of attack, the good agreement between fluent's data and digital Datcom's data is observed. Digital Datcom's data can be used to obtain aerodynamic coefficients during the design phase. At all angles of attack, the airship has static stability and at low angles of attack, it has the least stability and maximum maneuverability. The drag coefficient obtained from Digital Datcom has a significant difference with the Fluent and other references data. therefore, Digital Datcom cannot be predicted at design phases for the drag coefficient.

journal of Aerospace Science and Technology, 2021

In the present study, the aerodynamic performance of the ducted fan is investigated using the sur... more In the present study, the aerodynamic performance of the ducted fan is investigated using the surface vorticity method and the lifting line theory. In previous research, to consider the effects of the duct, most of the parameters derived from empirical tests or computational fluid dynamics. Our goal is to present a new method for considering the effects of the duct on the fan enclosed in a duct. In this method, the lift and drag coefficients are only input parameters. The present method requires considerably less computational time than CFD methods. Also, the aerodynamic optimization of fan blades geometry has been carried out using particle swarm optimization method (PSO) to achieve the optimum blade geometry and the maximum output power. The results of this method are in excellent agreement with experimental data in references. By optimizing the geometry of the blade, the output power of ducted fan increased 10 percentage in comparison to ducted fan with old blade geometry

In this research, canard and its vertical and longitudinal positions effects on pressure distribu... more In this research, canard and its vertical and longitudinal positions effects on pressure distribution and aerodynamic coefficients of a maneuverable aircraft wing model have been investigated numerically applying the fluent software. The investigations have been performed at the Reynolds number of 5×105 and different angles of attack, using unstructured grid and the Reynolds stress modeling. The applied wing and canard are delta shape and the supposed canard longitudinal positions are front, middle and rear, and its vertical positions are up, middle and low, respect to the main delta wing. For the case of no canard configuration model, the obtained results show that until angle of attack of 25 degrees, there is a very good agreement between the experimental data and the numerical results. Adding the canard causes the vortex on the wing upper surface become stronger and bigger. Also, for all longitudinal and vertical positions of the canard, the canard’s wake passes over the main win...

In this study, the behavior of a subject consisting of a cylinder with 4 plates perpendicular to ... more In this study, the behavior of a subject consisting of a cylinder with 4 plates perpendicular to it with a rotational degree of freedom under airflow both through the numerical approach, known as improved discrete vortex and experimental approach were investigated. The experimental and numerical results have shown that oscillating regime occurs in low velocity and length. This movement is vibrations with irregular range around an equilibrium angle of 45 degree. In oscillating motion regime, it is seen that after releasing the object in free flow, a high torque force, due to the flow’s acceleration from the model, is induced to the plates and makes a big angular change, but after a while, the range of oscillation around the equilibrium angle of 45 degree decreases. The probability of rotational motion regime in length ratio of one and velocity of 13 m/sec in initial angle of attack is low. However, the experimental and numerical results have indicated that still in high initial angle...

Amirkabir Journal of Mechanical Engineering, 2019

In this study, the effect of steady spanwise blowing on the aerodynamic coefficients of a maneuve... more In this study, the effect of steady spanwise blowing on the aerodynamic coefficients of a maneuverable aircraft wing model have been simulated three dimensionally applying the fluent software. The simulations have been performed at the Mach number of 0.4 and different angles of attack, using unstructured grid and the k-w SSTturbulence model. Numerical simulation results showed that the spanwise blowing along the wing leading edge caused a flow along the axis of leading edge vortex and delayed the vortex breakdown until the high angles of attack. As a result, the lift coefficient increases at higher angles of attack, which is directly related to the jet momentum coefficient. By applying blowing, due to the vortex breakdown on the wing surface, drag coefficient is greater in comparison to the no blowing condition until the angle of attack 24 degree and after this angle, the drag coefficient decreases. Also, drag coefficient decrease is lower at greater jet momentum coefficients. By injecting the flow over the wing, the vortex increases in different longitudinal sections and causes
a greater pressure drop on the upper surface of the wing. Also, the greatest amount of pressure in the inner span of the wing and near the edge of the wing attack is observed.

Modares Mechanical Engineering, 2020

[1] Rocket propulsion elements [2] Liquid injection thrust vector control and effective parameter... more [1] Rocket propulsion elements [2] Liquid injection thrust vector control and effective parameters [3] An experimental investigation of thrust vector control by secondary injection [4] Analysis of performance of hot gas injection thrust vector control system [5] Comparison of Euler and navier-stokes solutions for nozzle flows with secondary injection [6] Jet tab thrust vector control [7] Jet tab thrust vector control system demonstration [8] The flow generated by ramp tabs in a rocket nozzle exhaust [9] Effects of vortex generating tabs on noise sources in an ideally expanded Mach 1.3 jet [10] Corrugated tabs for supersonic jet control [11] A computational study of thrust vectoring control using dual throat nozzle [12] Thrust shock vector control of an axisymmetric conical supersonic nozzle via secondary transverse gas injection [13] Numerical simulation of fluidic thrust vectoring in an axisymmetric supersonic nozzle [14] Large eddy simulation of shock vector control using bypass flow passage [15] CFD modeling for flow field characterization and performance analysis of HGITVC [16] Experimental and simulation testing of thermal loading in the jet tabs of a thrust vector control system [17] experimental investigation of the effect of cylindrical protuberance with different penetration the thrust vector a c-d nozzle in supersonic regime [18] Turbulent jet in crossflow analysis with LES approach [19] New visions in experimental investigations of a supersonic under-expanded jet into a high subsonic crossflow [20] Detailed flow physics of the supersonic jet interaction flow field In this research, the effect of several unconventional obstructions with cubic, spherical, cylindrical, and cone geometries on the propulsion vector of a convergent-divergent micro nozzle as a new method in propulsion vector control is experimentally investigated. For this purpose, a convergent-divergent nozzle was designed and constructed in small dimensions. This nozzle is such that the Mach number is its nominal output in full expansion conditions 2. The wall of this nozzle is designed to measure pressure variations with pressure holes. Also, in the nozzle wall, a duct has been created to apply a bulge inside the nozzle. Pressure sensors and the shadograph system have been used to pressure measurement and check the outlet flow field respectively. The total pressure of the calming chamber is constant in all experiments and is equal to 5.5 times. The results of this study show that the maximum deviation is related to an obstruction with a cubic geometry which is 2.1 degrees. Also, the geometries that have sharp corners are more shock-shaped and hit the opposite wall. In this research, the shock formed by a cubic barrier has hit the opposite wall, but with a spherical shaped and cone-shaped barrier, the shock comes out from the nozzle. Also, these results indicate that the axial force of the nozzle has been reduced to a very small extent.

JOURNAL OF SOLID AND FLUID MECHANIC, 2017

In this research, canard and its vertical and longitudinal positions effects on pressure distribu... more In this research, canard and its vertical and longitudinal positions effects on pressure distribution and aerodynamic coefficients of a maneuverable aircraft wing model have been investigated numerically applying the fluent software. The investigations have been performed at the Reynolds number of 5×10 5 and different angles of attack, using unstructured grid and the Reynolds stress modeling. The applied wing and canard are delta shape and the supposed canard longitudinal positions are front, middle and rear, and its vertical positions are up, middle and low, respect to the main delta wing. For the case of no canard configuration model, the obtained results show that until angle of attack of 25 degrees, there is a very good agreement between the experimental data and the numerical results. Adding the canard causes the vortex on the wing upper surface become stronger and bigger. Also, for all longitudinal and vertical positions of the canard, the canard's wake passes over the main wing surface. When the canard is at forward-up position respect to the main wing, the highest amount of lift force achieves. Furthermore, the least amount of drag force relates to the case which the canard is closer to the main wing and along with its axis. However, maximum amount of aerodynamic performance achieves when canard is at down-forward position respect to the main delta wing.

Journal of Aeronautical Engineering, 2018

In this research, the experimental investigation of unsteady flow around a cylinder model with th... more In this research, the experimental investigation of unsteady flow around a cylinder model with three plates perpendicular to it has been discussed. This study has been done at different speeds, primary model angle of attacks and length ratios. The results show that the model has steady and unsteady oscillation and rotational motions. These types of behaviors depend on the plate's length ratio, primary object angle of attack, and free stream velocity. The model has damping motion around an angle of 60 degree, at low speed and length ratio. The greatest oscillational or rotational flow has appeared at initial angle of attack of 0 degree. In low length ratio, the regime of motion is oscillations that it changed to rotational motion when the length ratio and free stream velocity increase. The variation of angular velocity at length ratio of 1 and 4, with respect to time, are accompanied with reduction of vibrations range per motion. Also, over time, the vibrational velocity of the model is reduced. In addition, the results show that by increasing the Reynolds Number, Strouhal number becomes constant.

In this research, canard and its vertical and longitudinal positions effects on pressure distribu... more In this research, canard and its vertical and longitudinal positions effects on pressure distribution and aerodynamic coefficients of a maneuverable aircraft wing model have been investigated numerically applying the fluent software. The investigations have been performed at the Reynolds number of 5×105 and different angles of attack, using unstructured grid and the Reynolds stress modeling. The applied wing and canard are delta shape and the supposed canard longitudinal positions are front, middle and rear, and its vertical positions are up, middle and low, respect to the main delta wing. For the case of no canard configuration model, the obtained results show that until angle of attack of 25 degrees, there is a very good agreement between the experimental data and the numerical results. Adding the canard causes the vortex on the wing upper surface become stronger and bigger. Also, for all longitudinal and vertical positions of the canard, the canard’s wake passes over the main wing surface. When the canard is at forward-up position respect to the main wing, the highest amount of lift force achieves. Furthermore, the least amount of drag force relates to the case which the canard is closer to the main wing and along with its axis. However, maximum amount of aerodynamic performance achieves when canard is at down-forward position respect to the main delta wing.

A series of experiments are conducted to study the velocity field around a wing- canard body that... more A series of experiments are conducted to study the velocity field around a wing- canard body that represents a highly maneuverable aircraft. All experiments were conducted in a subsonic wind tunnel under two different angle of attack, α_model=15,20 degrees, while the canard angle of attack varied between -10 to 10 degrees. The data shows that, at all the angles of attack mentioned before, the canard downwash passes over the main wing surface, which results in a reduction of the pressure over the wing surface. These phenomena delay the model stall angle of attack, hence, increasing the performance of the model. Furthermore, to reduce the experiments, a neural network system was used, which is capable of both prediction and extrapolation. The neural network data shows both canard and main wing vortices at various stations over the wing surface. As the canard angle stronger and cover a layer portion of the wing surface. As a result of this vortex system, the pressure over the wing surface drops considerably.