Mahmood Pasandideh Fard | Ferdowsi University of Mashhad (original) (raw)
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Papers by Mahmood Pasandideh Fard
Journal of Applied and Computational Sciences in Mechanics, 2011
In this paper using one, two and three dimensional simulations, the accelerating flows in develop... more In this paper using one, two and three dimensional simulations, the accelerating flows in developing inlet pipe region are considered numerically. The developing length calculated based on different turbulence parameters is studied thoroughly. The SST turbulence model in comparison with recent reported experimental data have been used to achieve reliable predictions. The predictions obtained using all 1, 2, and 3 dimensional cases are generally the same and follow the experiments well. Thus, it seems that one dimensional simulation in fully developed region is sufficient. However, for the inlet region in developing state a two dimensional axisymmetric analysis is required. This research shows that calculating the developing length based on only mean averaged velocity is not adequate, but also turbulence kinetic energy and viscosity must be paid enough attention. Further, the comparison between steady and unsteady flows for the developing length shows that they are very different. This length also depends on both the value of flow acceleration and turbulence delay time in addition to Reynolds number and pipe diameter.
Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
One of the frequently reported defects of RANS-based turbulence models is overestimation of turbu... more One of the frequently reported defects of RANS-based turbulence models is overestimation of turbulent kinetic energy production in high speed separated flow problems, which causes significant prediction errors. The correct estimation of such flow in thrust optimized parabolic nozzles extremely depends upon the accurate prediction of the onset of flow separation. In this paper, firstly, the significant error of conventional RANS-based turbulence models is shown to predict the onset of flow separation in this type of nozzles. Then, the prediction accuracy is improved through the modification of the essential parameters of the generalized k-ω (GEKO) turbulence model. It was found that modifying the separation and mixing parameters of the GEKO model to realize the turbulent kinetic energy production resulted in the accurate prediction of onset of flow separation at the extensive range of nozzle pressure ratios. Using this modified model with new coefficients reduced the error of about 3...
This paper deals with an adaptive dynamic grid around oscillationg airfoils and compares Roe upwi... more This paper deals with an adaptive dynamic grid around oscillationg airfoils and compares Roe upwind methods, with scalar and CUSP central difference schemes. Euler equations have been solved for the external invisid compressible flow. Thus, at first, the equations were written ...
In this paper, the aero heating of spherical stagnation point is studied. For this purpose, we fi... more In this paper, the aero heating of spherical stagnation point is studied. For this purpose, we first calculate the thermodynamic properties behind of the normal shock, for the supersonic flow of the hot gas. After finding these properties, we are able to calculate the boundary layer ...
A numerical unsteady approach is fallowed to simulate ventilated cavitation behind an axisymmtric... more A numerical unsteady approach is fallowed to simulate ventilated cavitation behind an axisymmtric body. In this study liquid-gas interface is modeled, using the volume of fluid (VOF) method based on young's algorithm. Transient Navier-Stokes equations are solved along with an equation to track the cavity interface. Turbulent fluctuations in the velocity field are modeled using the Reynolds Averaged Navier-Stokes (RANS) methodology. Turbulence is assumed to be isotropic and k RNG turbulence model is used in this investigation. Different free stream velocities are considered. First, the results for variation of cavity length with cavitation number have been compared to the available experimental data for a two-dimensional wedge. The good agreement between the computational and experimental results validates the present numerical method. Then this method has been used to simulate the ventilated cavitation behind a cone with the same chord and angle as the wedge. Simulation shows that, the cavity length will increase by decreasing the cavitation number. The results show that at the same cavitation numbers, the cavity lengths of the wedge are longer than those of the cone.
In this paper simulation of cavitating flow over the Clark-Y hydrofoil is reported using computat... more In this paper simulation of cavitating flow over the Clark-Y hydrofoil is reported using computational fluid dynamics (CFD) technique. This simulation is performed using the large eddy simulation (LES) turbulence model. We applied an incompressible LES modeling approach based on an implicit method for the subgrid terms. To apply the cavitation model, the flow has been considered as a single fluid, two-phase mixture. A transport equation model for the local volume fraction of vapor is solved with the LES model and a finite rate mass transfer model is used for the vaporization and condensation processes. The volume of fluid (VOF) method is applied to track the interface of liquid and vapor phases. This simulation is performed using a two phase solver available in the framework of the OpenFOAM (open field operation and Manipulation) software package, namely "interPhaseChangeFoam". The solver is based on the finite volume method. Simulation is performed for the cloud and super cavitation regimes. The results of our simulation are compared with the experimental data and the accuracy of the simulation has been investigated.
The flight dynamics of nine configurations of supersonic continuous deflectable nose guided missi... more The flight dynamics of nine configurations of supersonic continuous deflectable nose guided missiles have been investigated. The studied configurations consist of a spherical nose tip, a tangent ogive, a set of stabilizing tail fins and a cylindrical body having mid-section flexible enough to form an arc of circle. So the cylindrical body consists of a fixed part in the vicinity of nose, middle flexible part and main body with stabilizers. The effects of fixed length and flexible length parameters on the flight dynamics of surface to surface, anti-aircraft and antimissile missiles have been studied. A code has been developed to solve full Navier-Stokes equations using finite volume and modified Baldwin-Lomax turbulence model. Further, a 3 degree of freedom code has been developed to compare planar flight dynamics of missiles. This code consists of a guidance subroutine based on pure pursuit law. The results show that even increase of fixed and flexible lengths enhance the maneuverability of the missile, but in some scenarios this can lead to increased flight time and more errors in the target engagement. Deflected nose relocates mass center away from the axis and a thrust vector torque is created. Study of surface to surface scenario shows that this torque improves accuracy of targeting and the ability of target dislocation. In air defense missiles, increase of Fix and Flex variables will extend the limits of allowable firing angle. However, a heavy nose increases the role of thrust torque and subsequently decreases the role of nose geometry.
Original Research Paper Received 12 March 2016 Accepted 30 May 2016 Available Online 13 July 2016... more Original Research Paper Received 12 March 2016 Accepted 30 May 2016 Available Online 13 July 2016 In this paper simulation of steady super cavitation phenomenon has been considered by using partial non-linear model of Boundary Element Method(BEM).The grid mesh used is fixed and the strength of dipole and source are constant on each element. With the assumption of a partial non-linear model the cavity condition is applied on the body with the assumption that cavity height is low. Thus there is not any calculation on the cavity surface, but it is restricted to only the panels on the body surface. Cavitation number is known at first and the cavity length is determined in every iteration. When the lengths obtained in two successive iterations are very close to each other it is assumed to be the answer. Based on this method two Kutta conditions including Morino condition and Iterative Pressure Kutta Condition(IPKC) are studied to satisfy the wake surface condition. The application is a w...
Iranian Journal of Science and Technology, Transactions of Mechanical Engineering
Progress in Computational Fluid Dynamics, An International Journal
سوخت و احتراق, Sep 12, 2008
Acta Crystallographica Section E Structure Reports Online, 2010
In this paper, the aero heating of spherical stagnation point is studied. For this purpose, we fi... more In this paper, the aero heating of spherical stagnation point is studied. For this purpose, we first calculate the thermodynamic properties behind of the normal shock, for the supersonic flow of the hot gas. After finding these properties, we can calculate the boundary layer properties and then we will be able to determine the heat flux of the spherical stagnation point. This heat flux can be used as a boundary condition in heat transfer code for axial asymmetric case. After computing transient multilayer heat transfer toward the inner side of the shell (which material varies in each layer), we can determine stagnation point temperature and temperature distribution in various layers. To verify the validity of the used numerical procedure in this work, comparisons with the theoretical and experimental results for the X-33 space vehicle have been conducted.
1395 16 12 67-78 mme.modares.ac.ir : Pleasecitethisarticleusing: M. Ghaffari, M. Pasandideh Fard,... more 1395 16 12 67-78 mme.modares.ac.ir : Pleasecitethisarticleusing: M. Ghaffari, M. Pasandideh Fard, M. Tabaki, Simulation of flow around axisymmetric projectiles with circular cavitator and ringed tip using control volume and boundary elementmethods,ModaresMechanicalEngineeringVol.16,No.12,pp.67-78,2016(inPersian) In this article, cavitation flow around axisymmetric projectiles with ringed and non-ringed cavitator has been investigated using control volume and boundary element methods. In the numerical method, the homogeneous equilibrium approach as well as the zwart model, for modeling the mass transfer and forming the system of equation, have been used. In the boundary element approach with dipole distribution on the body and cavity surfaces and source distribution on the cavity surface, the right conditions were set for using the Green's theorem in solving the potential flow. Moreover, some source components were imposed on the cavitator surface in order to add the hole effects...
Original Research Paper Received 12 March 2016 Accepted 30 May 2016 Available Online 13 July 2016... more Original Research Paper Received 12 March 2016 Accepted 30 May 2016 Available Online 13 July 2016 In this paper simulation of steady super cavitation phenomenon has been considered by using partial non-linear model of Boundary Element Method(BEM).The grid mesh used is fixed and the strength of dipole and source are constant on each element. With the assumption of a partial non-linear model the cavity condition is applied on the body with the assumption that cavity height is low. Thus there is not any calculation on the cavity surface, but it is restricted to only the panels on the body surface. Cavitation number is known at first and the cavity length is determined in every iteration. When the lengths obtained in two successive iterations are very close to each other it is assumed to be the answer. Based on this method two Kutta conditions including Morino condition and Iterative Pressure Kutta Condition(IPKC) are studied to satisfy the wake surface condition. The application is a w...
Journal of Applied and Computational Sciences in Mechanics, 2011
In this paper using one, two and three dimensional simulations, the accelerating flows in develop... more In this paper using one, two and three dimensional simulations, the accelerating flows in developing inlet pipe region are considered numerically. The developing length calculated based on different turbulence parameters is studied thoroughly. The SST turbulence model in comparison with recent reported experimental data have been used to achieve reliable predictions. The predictions obtained using all 1, 2, and 3 dimensional cases are generally the same and follow the experiments well. Thus, it seems that one dimensional simulation in fully developed region is sufficient. However, for the inlet region in developing state a two dimensional axisymmetric analysis is required. This research shows that calculating the developing length based on only mean averaged velocity is not adequate, but also turbulence kinetic energy and viscosity must be paid enough attention. Further, the comparison between steady and unsteady flows for the developing length shows that they are very different. This length also depends on both the value of flow acceleration and turbulence delay time in addition to Reynolds number and pipe diameter.
Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
One of the frequently reported defects of RANS-based turbulence models is overestimation of turbu... more One of the frequently reported defects of RANS-based turbulence models is overestimation of turbulent kinetic energy production in high speed separated flow problems, which causes significant prediction errors. The correct estimation of such flow in thrust optimized parabolic nozzles extremely depends upon the accurate prediction of the onset of flow separation. In this paper, firstly, the significant error of conventional RANS-based turbulence models is shown to predict the onset of flow separation in this type of nozzles. Then, the prediction accuracy is improved through the modification of the essential parameters of the generalized k-ω (GEKO) turbulence model. It was found that modifying the separation and mixing parameters of the GEKO model to realize the turbulent kinetic energy production resulted in the accurate prediction of onset of flow separation at the extensive range of nozzle pressure ratios. Using this modified model with new coefficients reduced the error of about 3...
This paper deals with an adaptive dynamic grid around oscillationg airfoils and compares Roe upwi... more This paper deals with an adaptive dynamic grid around oscillationg airfoils and compares Roe upwind methods, with scalar and CUSP central difference schemes. Euler equations have been solved for the external invisid compressible flow. Thus, at first, the equations were written ...
In this paper, the aero heating of spherical stagnation point is studied. For this purpose, we fi... more In this paper, the aero heating of spherical stagnation point is studied. For this purpose, we first calculate the thermodynamic properties behind of the normal shock, for the supersonic flow of the hot gas. After finding these properties, we are able to calculate the boundary layer ...
A numerical unsteady approach is fallowed to simulate ventilated cavitation behind an axisymmtric... more A numerical unsteady approach is fallowed to simulate ventilated cavitation behind an axisymmtric body. In this study liquid-gas interface is modeled, using the volume of fluid (VOF) method based on young's algorithm. Transient Navier-Stokes equations are solved along with an equation to track the cavity interface. Turbulent fluctuations in the velocity field are modeled using the Reynolds Averaged Navier-Stokes (RANS) methodology. Turbulence is assumed to be isotropic and k RNG turbulence model is used in this investigation. Different free stream velocities are considered. First, the results for variation of cavity length with cavitation number have been compared to the available experimental data for a two-dimensional wedge. The good agreement between the computational and experimental results validates the present numerical method. Then this method has been used to simulate the ventilated cavitation behind a cone with the same chord and angle as the wedge. Simulation shows that, the cavity length will increase by decreasing the cavitation number. The results show that at the same cavitation numbers, the cavity lengths of the wedge are longer than those of the cone.
In this paper simulation of cavitating flow over the Clark-Y hydrofoil is reported using computat... more In this paper simulation of cavitating flow over the Clark-Y hydrofoil is reported using computational fluid dynamics (CFD) technique. This simulation is performed using the large eddy simulation (LES) turbulence model. We applied an incompressible LES modeling approach based on an implicit method for the subgrid terms. To apply the cavitation model, the flow has been considered as a single fluid, two-phase mixture. A transport equation model for the local volume fraction of vapor is solved with the LES model and a finite rate mass transfer model is used for the vaporization and condensation processes. The volume of fluid (VOF) method is applied to track the interface of liquid and vapor phases. This simulation is performed using a two phase solver available in the framework of the OpenFOAM (open field operation and Manipulation) software package, namely "interPhaseChangeFoam". The solver is based on the finite volume method. Simulation is performed for the cloud and super cavitation regimes. The results of our simulation are compared with the experimental data and the accuracy of the simulation has been investigated.
The flight dynamics of nine configurations of supersonic continuous deflectable nose guided missi... more The flight dynamics of nine configurations of supersonic continuous deflectable nose guided missiles have been investigated. The studied configurations consist of a spherical nose tip, a tangent ogive, a set of stabilizing tail fins and a cylindrical body having mid-section flexible enough to form an arc of circle. So the cylindrical body consists of a fixed part in the vicinity of nose, middle flexible part and main body with stabilizers. The effects of fixed length and flexible length parameters on the flight dynamics of surface to surface, anti-aircraft and antimissile missiles have been studied. A code has been developed to solve full Navier-Stokes equations using finite volume and modified Baldwin-Lomax turbulence model. Further, a 3 degree of freedom code has been developed to compare planar flight dynamics of missiles. This code consists of a guidance subroutine based on pure pursuit law. The results show that even increase of fixed and flexible lengths enhance the maneuverability of the missile, but in some scenarios this can lead to increased flight time and more errors in the target engagement. Deflected nose relocates mass center away from the axis and a thrust vector torque is created. Study of surface to surface scenario shows that this torque improves accuracy of targeting and the ability of target dislocation. In air defense missiles, increase of Fix and Flex variables will extend the limits of allowable firing angle. However, a heavy nose increases the role of thrust torque and subsequently decreases the role of nose geometry.
Original Research Paper Received 12 March 2016 Accepted 30 May 2016 Available Online 13 July 2016... more Original Research Paper Received 12 March 2016 Accepted 30 May 2016 Available Online 13 July 2016 In this paper simulation of steady super cavitation phenomenon has been considered by using partial non-linear model of Boundary Element Method(BEM).The grid mesh used is fixed and the strength of dipole and source are constant on each element. With the assumption of a partial non-linear model the cavity condition is applied on the body with the assumption that cavity height is low. Thus there is not any calculation on the cavity surface, but it is restricted to only the panels on the body surface. Cavitation number is known at first and the cavity length is determined in every iteration. When the lengths obtained in two successive iterations are very close to each other it is assumed to be the answer. Based on this method two Kutta conditions including Morino condition and Iterative Pressure Kutta Condition(IPKC) are studied to satisfy the wake surface condition. The application is a w...
Iranian Journal of Science and Technology, Transactions of Mechanical Engineering
Progress in Computational Fluid Dynamics, An International Journal
سوخت و احتراق, Sep 12, 2008
Acta Crystallographica Section E Structure Reports Online, 2010
In this paper, the aero heating of spherical stagnation point is studied. For this purpose, we fi... more In this paper, the aero heating of spherical stagnation point is studied. For this purpose, we first calculate the thermodynamic properties behind of the normal shock, for the supersonic flow of the hot gas. After finding these properties, we can calculate the boundary layer properties and then we will be able to determine the heat flux of the spherical stagnation point. This heat flux can be used as a boundary condition in heat transfer code for axial asymmetric case. After computing transient multilayer heat transfer toward the inner side of the shell (which material varies in each layer), we can determine stagnation point temperature and temperature distribution in various layers. To verify the validity of the used numerical procedure in this work, comparisons with the theoretical and experimental results for the X-33 space vehicle have been conducted.
1395 16 12 67-78 mme.modares.ac.ir : Pleasecitethisarticleusing: M. Ghaffari, M. Pasandideh Fard,... more 1395 16 12 67-78 mme.modares.ac.ir : Pleasecitethisarticleusing: M. Ghaffari, M. Pasandideh Fard, M. Tabaki, Simulation of flow around axisymmetric projectiles with circular cavitator and ringed tip using control volume and boundary elementmethods,ModaresMechanicalEngineeringVol.16,No.12,pp.67-78,2016(inPersian) In this article, cavitation flow around axisymmetric projectiles with ringed and non-ringed cavitator has been investigated using control volume and boundary element methods. In the numerical method, the homogeneous equilibrium approach as well as the zwart model, for modeling the mass transfer and forming the system of equation, have been used. In the boundary element approach with dipole distribution on the body and cavity surfaces and source distribution on the cavity surface, the right conditions were set for using the Green's theorem in solving the potential flow. Moreover, some source components were imposed on the cavitator surface in order to add the hole effects...
Original Research Paper Received 12 March 2016 Accepted 30 May 2016 Available Online 13 July 2016... more Original Research Paper Received 12 March 2016 Accepted 30 May 2016 Available Online 13 July 2016 In this paper simulation of steady super cavitation phenomenon has been considered by using partial non-linear model of Boundary Element Method(BEM).The grid mesh used is fixed and the strength of dipole and source are constant on each element. With the assumption of a partial non-linear model the cavity condition is applied on the body with the assumption that cavity height is low. Thus there is not any calculation on the cavity surface, but it is restricted to only the panels on the body surface. Cavitation number is known at first and the cavity length is determined in every iteration. When the lengths obtained in two successive iterations are very close to each other it is assumed to be the answer. Based on this method two Kutta conditions including Morino condition and Iterative Pressure Kutta Condition(IPKC) are studied to satisfy the wake surface condition. The application is a w...