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This paper reviews the aero-vibro-acoustic theory required to predict interior wind noise in an automobile passenger cabin. It describes how the exterior flow field needs to be defined as an input source to a statistical energy analysis (SEA) model of the body structural acoustics, with particular emphasis on separation of different wavenumber components. The paper then presents and evaluates the most recent work with unsteady computational fluid dynamics (CFD), as means to provide the required inputs to the SEA model. Comparison of predictions with test data is provided to illustrate progress to date and continuing development directions.

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.

The flow structures about a car-like bluff body with a variety of after-body configurations are numerically studied based on a finite-volume solution method with the sub-grid scale turbulence model. The numerical calculations are compared with the experiments in both the water basin and wind tunnel. Different detachment features are demonstrated in the case of different after-body configuration by the numerical analysis and the computer-graphics visualization. Some critical features such as high and low drag states are revealed in the numerical simulation in the case of critical-angle configuration and their mechanism are discussed.

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.

A newly developed finite-difference solution method TUMMAC-VII is applied to the flow about a road vehicle. It is a time-marching solution method for the Navier-Stokes equation in the framework of a fixed rectangular coordinate system. The no-slip boundary conditions are implemented in the body boundary cells. The use of a subgrid-scale turbulence model enables us to resolve the structure of the 3D vortical flows past road vehicles. Simulation is performed for the Ahmed model as well as the GEOSTORM model with a quarter and a half-million grid points, respectively, and the results are compared with experimental results.