Calculation Process with Lattice Boltzmann and Finite Element Methods to Choose the Best Exterior Design for Wind Noise

Wind noise in automobile is becoming more and more important as the customer expectations increase. On the other hand, great progress has been made on engine and road noises, especially for electric and hybrid vehicles. Thus, the wind noise is now by far the major acoustic source during road and motorway driving.

As for other noises, automobile manufacturers must be able, for a new car project, to specify, calculate and measure each step of the acoustic cascading:

• Source
• Transfers, both solid and air borne

In the case of the automotive wind noise, the excitation source is the dynamic pressure on the vehicle’s panels. This part of the cascading is the one influenced by the exterior design. Even if many others components (panels, seals, cabin trims) have a big influence, the exterior design is a major issue for the wind noise. The wind noise level in the cabin may change significantly with only a small modification of the exterior design.

This paper addresses the problem of doing the good choice of exterior design in the early phases of a new vehicle’ project, to reduce the wind noise. First, it reminds the industrial context for an automotive car manufacturer and the phenomenon existing in the coupling between a turbulent flow and a vehicle’s panel.

Then it presents a new numerical process based on the dynamic coupling of two models:

• Calculation of the flow and pressure around the vehicle with a solver based on the Lattice Boltzmann Method
• Vibration and acoustic radiated by the lateral window with a finite element model

The advantages, disadvantages and limits of the process are presented. Finally, the method is validated by comparison with wind tunnel measurements.