Ghader Ghorbaniasl - Profile on Academia.edu (original) (raw)
Papers by Ghader Ghorbaniasl
Noise prediction from a rotating cylinder in subcritical Reynolds flow
![Research paper thumbnail of Response to “Comment on ‘A self-adjusting flow dependent formulation for the classical Smagorinsky model coefficient’” [Phys. Fluids 25, 099101 (2013)]](https://attachments.academia-assets.com/123082160/thumbnails/1.jpg)
](Physics of Fluids, Sep 1, 2013
Proceedings of The Royal Society A: Mathematical, Physical and Engineering Sciences, Feb 1, 2018
This paper presents a time-domain method for noise prediction of supersonic rotating sources in a... more This paper presents a time-domain method for noise prediction of supersonic rotating sources in a moving medium. The proposed approach can be interpreted as an extensive time-domain solution for the convected permeable Ffowcs Williams and Hawkings equation, which is capable of avoiding the Doppler singularity. The solution requires special treatment for construction of the emission surface. The derived formula can explicitly and efficiently account for subsonic uniform constant flow effects on radiated noise. Implementation of the methodology is realized through the Isom thickness noise case and high-speed impulsive noise prediction from helicopter rotors.
The International Conference on Applied Mechanics and Mechanical Engineering, 2014
The majority of the adjoint methods applications focus on research in aerodynamic shape design op... more The majority of the adjoint methods applications focus on research in aerodynamic shape design optimization such as flow in airfoil cascade. This paper presents the application of the adjoint method technique in simple test cases of engineering relevance. The goal of this work is to extend the adjoint method into more engineering applications for viscous and incompressible flow, and to further improve the performance. Two test cases of engineering relevance have been selected. (1) Mesh adaptation for 2-D lid-driven cavity. (2) Drag reduction using an optimized upstream rod. The adjoint method has been used to efficiently adapt the 2-D liddriven cavity mesh to minimize the discretization errors in calculating the swirl number. Based on the adaptation for the sensitivity magnitude, a uniform mesh of 1600 cells has been refined until a total 6586 cells, with finer mesh at the locations of highest sensitivities. The application of the adjoint method for the passive drag reduction problem results in a modified shape and position for the upstream cylinder. This change reduces the drag force on the main cylinder by 46%.
16th AIAA/CEAS Aeroacoustics Conference, 2010
The filtered fluid dynamic equations are discretized in space by a high-order spectral difference... more The filtered fluid dynamic equations are discretized in space by a high-order spectral difference (SD) method coupled with large eddy simulation (LES) approach. The subgridscale stress tensor is modeled by the wall-adapting local eddy-viscosity model (WALE). We solve the unsteady equations by advancing in time using a second-order backward difference formulae (BDF2) scheme. The nonlinear algebraic system arising from the time discretization is solved with the nonlinear lower-upper symmetric Gauss-Seidel (LU-SGS) algorithm. The SD-LES method provides the acoustic sources for aerodynamic sound field simulation in the time domain. The numerical noise simulation is based on the Ffowcs-Williams Hawkings (FW-H) approach, which provides noise contributions for monopole, dipole and quadrupole acoustic sources. This paper will focus on the validation and assessment of this hybrid approach using different test cases. The test cases used are: a laminar flow over a two-dimensional (2D) open cavity at Re = 1.5 × 10 3 and M = 0.15 and a laminar flow past a 2D square cylinder at Re = 200 and M = 0.5. In order to show the application of the numerical method in industrial cases and to assess its capability for sound field simulation, a three-dimensional (3D) turbulent flow in a muffler at Re = 4.665 × 10 4 and M = 0.05 has been chosen as a third test case. The flow results show good agreement with numerical and experimental reference solutions. Comparison of the computed noise results with those of reference solutions also shows that the numerical approach predicts noise accurately.
16th AIAA/CEAS Aeroacoustics Conference, 2010
An innovative aeroacoustic prediction method for Contra-Rotating Open Rotors (CROR) based on the ... more An innovative aeroacoustic prediction method for Contra-Rotating Open Rotors (CROR) based on the nonlinear harmonic method (NLH) for the CFD computations and on the Ffowcs Williams and Hawkings (FW-H) equations for the far-field acoustic propagation is described. This method is tested on a generic 8 × 8 puller CROR at typical take-off conditions. The outstanding efficiency of the prediction method in terms of CPU cost is demonstrated in this study. An analysis of the aerodynamic interactions between the two rotors as well as of the aeroacoustic field radiated in the far-field is presented, allowing for an improved understanding of noise generation mechanisms.
Acoustic velocity formulation for Kirchhoff data surfaces
International Journal of Aeroacoustics, 2015
ABSTRACT This paper deals with the derivation of an analytical time-domain formulation for the pr... more ABSTRACT This paper deals with the derivation of an analytical time-domain formulation for the prediction of the acoustic velocity field generated by moving bodies in a medium at rest, according to the Kirchhoff method. The present formulation can be implemented in acoustic pressure codes based on the Farassat's Kirchhoff formula for arbitrary moving bodies, thus allowing direct and fast calculation of the acoustic velocity field in scattering problems. For validation purposes, four test cases are considered, namely a three-dimensional monopole, dipole and quadrupole source, as well as a monopole in uniform flow. Comparison of the results with the analytical solutions proves the remarkable accuracy of the present formulation.
Validation of a time domain formulation for propeller noise prediction
International Journal of Aeroacoustics, 2006
On the coupling between a high-order spectral difference method and large eddy simulation
Proc. V European Conference on Computational Fluid Dynamics ECCOMAS CFD, 2010
Abstract. The filtered fluid dynamic equations are discretized in space by a high-order spectral ... more Abstract. The filtered fluid dynamic equations are discretized in space by a high-order spectral difference (SD) method coupled with large eddy simulation (LES) approach. The subgrid-scale stress tensor is modelled by the wall-adapting local eddy-viscosity model (WALE). We solve the unsteady equations by advancing in time using a second-order backward difference formula (BDF2). The nonlinear algebraic system arising from the time discretization is solved with the nonlinear lower-upper symmetric Gauss-Seidel (LU-SGS) ...
Journal of Computational Physics, 2010
High-order spectral difference method Large eddy simulation Wall-adapting local eddy-viscosity mo... more High-order spectral difference method Large eddy simulation Wall-adapting local eddy-viscosity model Implicit LU-SGS algorithm a b s t r a c t
Validation and application of a far-field time domain formulation for fan noise prediction
11th AIAA/CEAS Aeroacoustics Conference, 2005
Sensitivity Study on Computational Parameters for the Prediction of Noise Generated by Counter-Rotating Open Rotors
17th AIAA/CEAS Aeroacoustics Conference (32nd AIAA Aeroacoustics Conference), 2011
Efficient Flow and Noise Prediction of Counter-Rotating Open Rotors
Verfication of Noise Prediction Through Acoustic Analogy
13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference), 2007
Journal of Computational Physics, 2010
High-order spectral difference method Large eddy simulation Wall-adapting local eddy-viscosity mo... more High-order spectral difference method Large eddy simulation Wall-adapting local eddy-viscosity model Implicit LU-SGS algorithm a b s t r a c t
Journal of Computational Physics, 2011
Journal of Aerosol Science, 2012
Deposition of mono-disperse aerosols is studied numerically on a simplified human upper airway mo... more Deposition of mono-disperse aerosols is studied numerically on a simplified human upper airway model (UAM). This paper presents new correction functions for eddy interaction model (EIM) in an attempt to improve the accuracy of predicting aerosol deposition in the UAM. Based on an Euler-Lagrange methodology, the fluid phase is solved using RANS (Reynolds Averaged Navier Stokes equation) and employing low-Reynolds SST k-o turbulence model. The particle phase is solved using Lagrangian approach and employing an EIM model. Mono-disperse particle sizes of 3 and 6 mm are considered for breathing rates of 30 and 60 L/min.
Journal of Computational Physics, 2009
Study of the sediment transport over flat and wavy bottom using large-eddy simulation
Journal of Turbulence, 2009
... Chang, YS and Scotti, A. 2003. Entrainment and suspension of sediments into a turbulent flow ... more ... Chang, YS and Scotti, A. 2003. Entrainment and suspension of sediments into a turbulent flow over ripples. ... [44. Nakagawa, S., Na, Y. and Hanratty, TJ 2003. Influence of a wavy boundary on turbulence. ... Direct numerical simulation of turbulent flow over a wavy wall. Phys. ...
A moving medium formulation for prediction of propeller noise at incidence
Journal of Sound and Vibration, 2012
This paper presents a time domain formulation for the sound field radiated by moving bodies in a ... more This paper presents a time domain formulation for the sound field radiated by moving bodies in a uniform steady flow with arbitrary orientation. The aim is to provide a formulation for prediction of noise from body so that effects of crossflow on a propeller can be modeled in the time domain. An established theory of noise generation by a moving source is combined with the moving medium Green's function for derivation of the formulation. A formula with Doppler factor is developed because it is more easily interpreted and is more helpful in examining the physic of systems. Based on the technique presented, the source of asymmetry of the sound field can be explained in terms of physics of a moving source. It is shown that the derived formulation can be interpreted as an extension of formulation 1 and 1A of Farassat based on the Ffowcs Williams and Hawkings (FW-H) equation for moving medium problems. Computational results for a stationary monopole and dipole point source in moving medium, a rotating point force in crossflow, a model of helicopter blade at incidence and a propeller case with subsonic tips at incidence verify the formulation.
Noise prediction from a rotating cylinder in subcritical Reynolds flow
Physics of Fluids, Sep 1, 2013
Proceedings of The Royal Society A: Mathematical, Physical and Engineering Sciences, Feb 1, 2018
This paper presents a time-domain method for noise prediction of supersonic rotating sources in a... more This paper presents a time-domain method for noise prediction of supersonic rotating sources in a moving medium. The proposed approach can be interpreted as an extensive time-domain solution for the convected permeable Ffowcs Williams and Hawkings equation, which is capable of avoiding the Doppler singularity. The solution requires special treatment for construction of the emission surface. The derived formula can explicitly and efficiently account for subsonic uniform constant flow effects on radiated noise. Implementation of the methodology is realized through the Isom thickness noise case and high-speed impulsive noise prediction from helicopter rotors.
The International Conference on Applied Mechanics and Mechanical Engineering, 2014
The majority of the adjoint methods applications focus on research in aerodynamic shape design op... more The majority of the adjoint methods applications focus on research in aerodynamic shape design optimization such as flow in airfoil cascade. This paper presents the application of the adjoint method technique in simple test cases of engineering relevance. The goal of this work is to extend the adjoint method into more engineering applications for viscous and incompressible flow, and to further improve the performance. Two test cases of engineering relevance have been selected. (1) Mesh adaptation for 2-D lid-driven cavity. (2) Drag reduction using an optimized upstream rod. The adjoint method has been used to efficiently adapt the 2-D liddriven cavity mesh to minimize the discretization errors in calculating the swirl number. Based on the adaptation for the sensitivity magnitude, a uniform mesh of 1600 cells has been refined until a total 6586 cells, with finer mesh at the locations of highest sensitivities. The application of the adjoint method for the passive drag reduction problem results in a modified shape and position for the upstream cylinder. This change reduces the drag force on the main cylinder by 46%.
16th AIAA/CEAS Aeroacoustics Conference, 2010
The filtered fluid dynamic equations are discretized in space by a high-order spectral difference... more The filtered fluid dynamic equations are discretized in space by a high-order spectral difference (SD) method coupled with large eddy simulation (LES) approach. The subgridscale stress tensor is modeled by the wall-adapting local eddy-viscosity model (WALE). We solve the unsteady equations by advancing in time using a second-order backward difference formulae (BDF2) scheme. The nonlinear algebraic system arising from the time discretization is solved with the nonlinear lower-upper symmetric Gauss-Seidel (LU-SGS) algorithm. The SD-LES method provides the acoustic sources for aerodynamic sound field simulation in the time domain. The numerical noise simulation is based on the Ffowcs-Williams Hawkings (FW-H) approach, which provides noise contributions for monopole, dipole and quadrupole acoustic sources. This paper will focus on the validation and assessment of this hybrid approach using different test cases. The test cases used are: a laminar flow over a two-dimensional (2D) open cavity at Re = 1.5 × 10 3 and M = 0.15 and a laminar flow past a 2D square cylinder at Re = 200 and M = 0.5. In order to show the application of the numerical method in industrial cases and to assess its capability for sound field simulation, a three-dimensional (3D) turbulent flow in a muffler at Re = 4.665 × 10 4 and M = 0.05 has been chosen as a third test case. The flow results show good agreement with numerical and experimental reference solutions. Comparison of the computed noise results with those of reference solutions also shows that the numerical approach predicts noise accurately.
16th AIAA/CEAS Aeroacoustics Conference, 2010
An innovative aeroacoustic prediction method for Contra-Rotating Open Rotors (CROR) based on the ... more An innovative aeroacoustic prediction method for Contra-Rotating Open Rotors (CROR) based on the nonlinear harmonic method (NLH) for the CFD computations and on the Ffowcs Williams and Hawkings (FW-H) equations for the far-field acoustic propagation is described. This method is tested on a generic 8 × 8 puller CROR at typical take-off conditions. The outstanding efficiency of the prediction method in terms of CPU cost is demonstrated in this study. An analysis of the aerodynamic interactions between the two rotors as well as of the aeroacoustic field radiated in the far-field is presented, allowing for an improved understanding of noise generation mechanisms.
Acoustic velocity formulation for Kirchhoff data surfaces
International Journal of Aeroacoustics, 2015
ABSTRACT This paper deals with the derivation of an analytical time-domain formulation for the pr... more ABSTRACT This paper deals with the derivation of an analytical time-domain formulation for the prediction of the acoustic velocity field generated by moving bodies in a medium at rest, according to the Kirchhoff method. The present formulation can be implemented in acoustic pressure codes based on the Farassat's Kirchhoff formula for arbitrary moving bodies, thus allowing direct and fast calculation of the acoustic velocity field in scattering problems. For validation purposes, four test cases are considered, namely a three-dimensional monopole, dipole and quadrupole source, as well as a monopole in uniform flow. Comparison of the results with the analytical solutions proves the remarkable accuracy of the present formulation.
Validation of a time domain formulation for propeller noise prediction
International Journal of Aeroacoustics, 2006
On the coupling between a high-order spectral difference method and large eddy simulation
Proc. V European Conference on Computational Fluid Dynamics ECCOMAS CFD, 2010
Abstract. The filtered fluid dynamic equations are discretized in space by a high-order spectral ... more Abstract. The filtered fluid dynamic equations are discretized in space by a high-order spectral difference (SD) method coupled with large eddy simulation (LES) approach. The subgrid-scale stress tensor is modelled by the wall-adapting local eddy-viscosity model (WALE). We solve the unsteady equations by advancing in time using a second-order backward difference formula (BDF2). The nonlinear algebraic system arising from the time discretization is solved with the nonlinear lower-upper symmetric Gauss-Seidel (LU-SGS) ...
Journal of Computational Physics, 2010
High-order spectral difference method Large eddy simulation Wall-adapting local eddy-viscosity mo... more High-order spectral difference method Large eddy simulation Wall-adapting local eddy-viscosity model Implicit LU-SGS algorithm a b s t r a c t
Validation and application of a far-field time domain formulation for fan noise prediction
11th AIAA/CEAS Aeroacoustics Conference, 2005
Sensitivity Study on Computational Parameters for the Prediction of Noise Generated by Counter-Rotating Open Rotors
17th AIAA/CEAS Aeroacoustics Conference (32nd AIAA Aeroacoustics Conference), 2011
Efficient Flow and Noise Prediction of Counter-Rotating Open Rotors
Verfication of Noise Prediction Through Acoustic Analogy
13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference), 2007
Journal of Computational Physics, 2010
High-order spectral difference method Large eddy simulation Wall-adapting local eddy-viscosity mo... more High-order spectral difference method Large eddy simulation Wall-adapting local eddy-viscosity model Implicit LU-SGS algorithm a b s t r a c t
Journal of Computational Physics, 2011
Journal of Aerosol Science, 2012
Deposition of mono-disperse aerosols is studied numerically on a simplified human upper airway mo... more Deposition of mono-disperse aerosols is studied numerically on a simplified human upper airway model (UAM). This paper presents new correction functions for eddy interaction model (EIM) in an attempt to improve the accuracy of predicting aerosol deposition in the UAM. Based on an Euler-Lagrange methodology, the fluid phase is solved using RANS (Reynolds Averaged Navier Stokes equation) and employing low-Reynolds SST k-o turbulence model. The particle phase is solved using Lagrangian approach and employing an EIM model. Mono-disperse particle sizes of 3 and 6 mm are considered for breathing rates of 30 and 60 L/min.
Journal of Computational Physics, 2009
Study of the sediment transport over flat and wavy bottom using large-eddy simulation
Journal of Turbulence, 2009
... Chang, YS and Scotti, A. 2003. Entrainment and suspension of sediments into a turbulent flow ... more ... Chang, YS and Scotti, A. 2003. Entrainment and suspension of sediments into a turbulent flow over ripples. ... [44. Nakagawa, S., Na, Y. and Hanratty, TJ 2003. Influence of a wavy boundary on turbulence. ... Direct numerical simulation of turbulent flow over a wavy wall. Phys. ...
A moving medium formulation for prediction of propeller noise at incidence
Journal of Sound and Vibration, 2012
This paper presents a time domain formulation for the sound field radiated by moving bodies in a ... more This paper presents a time domain formulation for the sound field radiated by moving bodies in a uniform steady flow with arbitrary orientation. The aim is to provide a formulation for prediction of noise from body so that effects of crossflow on a propeller can be modeled in the time domain. An established theory of noise generation by a moving source is combined with the moving medium Green's function for derivation of the formulation. A formula with Doppler factor is developed because it is more easily interpreted and is more helpful in examining the physic of systems. Based on the technique presented, the source of asymmetry of the sound field can be explained in terms of physics of a moving source. It is shown that the derived formulation can be interpreted as an extension of formulation 1 and 1A of Farassat based on the Ffowcs Williams and Hawkings (FW-H) equation for moving medium problems. Computational results for a stationary monopole and dipole point source in moving medium, a rotating point force in crossflow, a model of helicopter blade at incidence and a propeller case with subsonic tips at incidence verify the formulation.