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Practical Aerodynamic Simulations (CD, CL, CYM) Using a Turbulence Model and 3rd-Order Upwind Scheme
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Abstract
Conventional aerodynamic simulations have been carried out by using Supercomputer and over a hundred thousand grid points. It takes a long CPU time to get a result. So this method has been mainly used as a research and demonstration tool.
In this paper a practical aerodynamic simulation for early phases of the automobile design is presented. This new method basically uses the conventional (wall function used) k-ε turbulent model which is regarded as the most promising in engineering and industrial fields.
Firstly, the third-order upwind scheme is introduced to the convective term to improve flow field and pressure distribution. Secondly, the modified turbulent energy production method (M.P.Method) which was proposed by B.E. Launder[3] in 1993, is introduced to the k-ε turbulent model to reduce the excessive generation of turbulent kinetic energy.
It takes 20 hours to generate a computational mesh from design CAD data by a new semi-automatic mesh generator and 10 hours to get the steady flow result by using EWS (IRIS Indigo2 R4400, 1CPU).
It takes only 4 days to get an aerodynamic solution within an error of 5% for CD (Drag Coefficient) and CL (Lift Coefficient). This new method has been applied to the aerodynamic simulation system, a designer has been able to carry out the practical simulation on early designing phase of an automobile.
We also present a CYM (Yawing Moment Coefficient) simulation between 0 and 45 degree and the influence of a outside rear view door mirror on Two-Box automobile.
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Okumura, K. and Kuriyama, T., "Practical Aerodynamic Simulations (CD, CL, CYM) Using a Turbulence Model and 3rd-Order Upwind Scheme," SAE Technical Paper 950629, 1995, https://doi.org/10.4271/950629.Also In
References
- Okumura K. Kuriyama T. Three-Dimensional Aerodynamic Simulations of Two-Box Automobile using Turbulence Model and QUICK Scheme 26th ISATA,Super Computer Applications in the Automobile Industries 45 52 1993-9
- van Leer, B. Toward the Ultimate Convection Difference Scheme.4,A New Approach to Numerical Convection Joumal of Computational Physics 23 276 299 1977
- Kato M. Launder BE The Modelling of Turbulent Flow around Stationary and vibrating Square Cylinders NINTH Symposium on TURBULENT FLOWS 16 18 1993-8
- Kobayashi Kito “A Review of CFD Methods and Their Application to Aerodynamics” SAE, 920338
- Kasagi N. et al. “Turbulence mesurementin a separated and reattaching flow over a backward-step with the aid of three-dimensional particle tracking velocimetry” 3rd Joint Symposium on Fluid Control and Mesurement Tokyo 1991
- Sumitani K. et al. Development “Aero Slit” Improvement of Aerodynamic Yaw Characteristics for Commercial Vehicles SAE, 890372
- Chapman Robert J. et al. Wind Noise and Aerodynamic Drag,Optimization of Outside Rear View Mirror SAE, 931292