Flow-induced Noise from Ground Vehicles - Problems and Prospects of Numerical Simulation

Abstract

The continuing increase in automobile and utility vehicle population in industrialised and developing countries has led to these vehicles being identified as the prime source of noise in urban areas and on the highways. Polls conducted over the years in Germany show that over 70% of the population currently feel subjected to serious annoyance through traffic noise. This result may also be true for other industrialised countries. Demands on comfort and prevention of noise induced fatigue during long driving periods is becoming an important car purchaser requirement. For the continued acceptance of automobiles in the future, car and utility vehicle manufacturers have to solve the technical problems involved in designing vehicles which are quieter both inside and outside. Even though the degree of discomfort through noise may be subjective, measurable quantities defining noise and means to reduce them are the engineering approach to reduce the annoyance impact of noise. This paper attempts to review the current technology available to predict the noise generated by the various sources on ground vehicles during their motion. The emphasis would be on flow induced noise and analysis of the noise generating mechanisms. From aerodynamic viewpoint, a ground vehicle is a bluff body moving in ground vicinity. The noise generated is the consequence of the complex flow field generated during its motion. A prediction of the overall flow with a detailed and correct physical description of the salient flow features is a prerequisite for an aeroacoustic computation and analysis. Problems and prospects for the CFD simulation of bluff body flows will be addressed.