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Surface pressure fluctuations on the front side window of a car-like body are numerically predicted by means of time-dependent Navier-Stokes simulation. The numerical results indicate that there is a critical inclination angle for the front pillar where the wind noise changes drastically. The related characteristics of turbulent flow structure are studied and show the mechanism of wind noise generation.

A numerical analysis method is developed for predicting the pressure fluctuations on the front side window surface, aiming at the elucidation of the external aerodynamic flow structure about the front pillar of a road vehicle. The simulated results are assessed by comparison with the acoustic theory and reveal fairly well the dependence of the predicted surface pressure fluctuations upon the vehicle cruising speed with the sixth power law. The features of three dimensional vortical flow are clarified from the analysis of the simulated results, indicating the strong relationship between the vortical formation and the external pressure fluctuations on the front side window surface. The external pressure fluctuations seem to be strongly related to the vortex breakdown during its interaction with the front side window and the roof-side window junction.

An experimental technique is developed for a vehicle moving steadily in the vicinity of the ground. A towing tank with a steadily advancing carriage is used and the unfavorable effects of the boundary layer on the ground which is inevitable in the case of a wind tunnel are fully removed. Experiments with a box-shaped model and a car model revealed some interesting features of lift, drag and side force at various clearances from the ground. Lift force is the most sensitive to the boundary layer and the lift measured in a wind tunnel may not completely represent lift on the road. The flow with vortices near the bottom surface of the body has one of the most important effects on the forces.

Numerical analysis of flow around the front end and in the engine compartment of FWD vehicles in three-dimension is presented. Finite - Volume Method is used for numerical integration of Navier-Stokes equations, incorporating k-ε model for turbulence. This method proved to be effective tool, showing good agreement of volume flow rate through radiator with experiments. Application of this method from the early stage of vehicle development contributed to significant saving of development term.