Unsteady RANS simulation of flow separation over Ahmed car model

Yao, J. and Mouzoun, O. and Yao, Y. and Mason, P. (2007) Unsteady RANS simulation of flow separation over Ahmed car model. In: emailDelicious Physics and Astronomy IUTAM Symposium on Unsteady Separated Flows and their Control. IUTAM Bookseries (closed), 14 (14). Springer, pp. 471-476. ISBN 9781402098970

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Full text URL: http://dx.doi.org/10.1007/978-1-4020-9898-7_40

Abstract

Three-dimensional separated flow around Ahmed car model has been studied by numerical simulation to solve the unsteady Reynolds-averaged Navier-Stokes (URANS) equations. The simulation considers experimental model with two slant angles of 25° and 35°. After some priori tests, baseline meshes have been identified with 1.5–1.9 × 106 elements for each case. After the precursor steady flow calculation, unsteady simulation continued for further two shedding cycles. Both mean and instantaneous quantities of the flow are accumulated and compared with available test data at representative measurement planes/locations. It was found that for two slant angles considered the time-averaged mean streamwise velocity of URANS predictions are compared fairly well with the experimental data with correct profile and same magnitude of peak. It was also observed that the slant angle has considerable influences on the downstream flow, particularly the flow recirculation, turbulence kinetic energy (TKE) distributions. The separated shear layers from the slant edges are merging together to form large size trailing vortex. While the flow structures agree qualitatively well with the measurement, the TKE has been under-estimated in wake region. This is mainly due to the limitation of two-equation turbulence model for massive separated flow with strong vortex shedding. Further advancement to large eddy simulation will provide a solution for

Item Type:Book Section
Additional Information:Three-dimensional separated flow around Ahmed car model has been studied by numerical simulation to solve the unsteady Reynolds-averaged Navier-Stokes (URANS) equations. The simulation considers experimental model with two slant angles of 25° and 35°. After some priori tests, baseline meshes have been identified with 1.5–1.9 × 106 elements for each case. After the precursor steady flow calculation, unsteady simulation continued for further two shedding cycles. Both mean and instantaneous quantities of the flow are accumulated and compared with available test data at representative measurement planes/locations. It was found that for two slant angles considered the time-averaged mean streamwise velocity of URANS predictions are compared fairly well with the experimental data with correct profile and same magnitude of peak. It was also observed that the slant angle has considerable influences on the downstream flow, particularly the flow recirculation, turbulence kinetic energy (TKE) distributions. The separated shear layers from the slant edges are merging together to form large size trailing vortex. While the flow structures agree qualitatively well with the measurement, the TKE has been under-estimated in wake region. This is mainly due to the limitation of two-equation turbulence model for massive separated flow with strong vortex shedding. Further advancement to large eddy simulation will provide a solution for
Keywords:Unsteady RANS - Ahmed model - Separated flow, Separated flow, Ahmed model, Unsteady RANS
Subjects:F Physical Sciences > F343 Computational Physics
H Engineering > H440 Aerodynamics
Divisions:College of Science > School of Engineering
ID Code:5438
Deposited By: Jun Yao
Deposited On:07 May 2012 21:20
Last Modified:07 May 2012 21:20

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