Numerical modelling techniques to optimise automotive-type panels for reduced sound radiation

Abstract

Numerical predictions are becoming ever more important in automotive development when analysing the Noise, Vibration and Harshness (NVH) performances of vehicles. In the low- to midfrequency range, vibro-acoustic predictions are generally performed using the finite element method (FEM) and/or boundary element method (BEM). In this paper, a numerical optimisation technique is described that aims at reducing the sound radiation from automotive-type panels over the frequency range of interest. The objective function, i.e. the radiated acoustic power, is calculated with a quadratic equation in terms of surface velocities. The genetic algorithm (GA) based optimisation aims to minimise the value of the objective function by modifying the normaldirection (Z-direction in an X-Y plane) of a few nodes of the finite element model of the panel, thereby imposing a geometrical change in the panel. The equation of an ellipsoid is used to smooth out the discontinuity after the change in the nodal coordinates and, hence, dome-shaped indentations are obtained. The resulting panel designs are analysed, both numerically and experimentally to support the approach presented.