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Passenger cars with sunroofs sometimes experience a low frequency pulsation noise called “wind throb” when traveling with the roof open. This “wind throb” should be suppressed because it is an unpleasant noise which can adversely affect the acoustic environment inside a car. In this paper, 3-dimensional numerical flow analysis is applied around a car body to investigate the wind throb phenomenon. The computational scheme and the modeling method of the car body is first described. A flow visualization test in a water tunnel was completed for the simple car body shape to compare against the numerical procedure. The numerical and the visualized results compared well and the numerical simulation method employed was considered to be a reliable tool to analyze the wind throb phenomenon. Calculated results of pressure and vorticity distribution in the sunroof opening were analyzed with the spectrum of pressure fluctuation at the sunroof opening with and without a deflector.

Aerodynamic drag reduction is one of the most important aspects of enhancing overall vehicle performance. Many car manufacturers have been working to establish drag reduction techniques. This paper describes the development process of a new small speciality car which achieved coefficient of drag(CD) of 0.25. A description of the test facilities and the systems used for developing the aerodynamic aspect of the car are also introduced briefly.

The influences of air way structures in engine cooling system on fan discrete noise were investigated. Each structures such as stays, horns and air leak preventive duct, affect the uniformity of inflow air distribution and the non uniformity of inflow air causes to fluctuate the lift of fan blades. This lift fluctuation results in the increasing of the discrete noise level from the fan. It is found that the exponent functional relations between discrete noise level and the velocity defect in the wake of structures. The possibility of predicting method of noise level from the engine cooling system was mentioned by using this functional relation.

Computational analysis of a flow field around a complex geometry such as a vehicle configuration becomes more reliable with the use of the most current numerical method. And the flow field around a vehicle with tires and wheel houses is simulated with accuracy. Recent market trends necessitate the use of aerodynamic devices to improve aerodynamic characteristics of a road vehicle. However, due to their complex shape, few computational studies of these devices have been performed. In this paper, a computational analysis system for vehicle aerodynamics is established and it's reliability is discussed. As the effective application of the system, the contribution of movable aerodynamic devices is studied using the system. And the comparison of wind tunnel test results with computational results is desirable.