Advance simulation method for aero-acoustic vehicle design

With the electrification of powertrains, the noise level inside vehicles reach high levels of silence. The dominant engine noise found in traditional vehicles is now replaced by other sources of noise such as rolling noise and aeroacoustic noise. These noises are encountered during driving on roads and highways and can cause significant fatigue during long journeys. Regarding aeroacoustic phenomena, the noise transmitted into the cabin is the result of both turbulent pressure and acoustic pressure created by the airflow. Even though it is lower in level, the acoustic pressure induces most of the noise perceived by the occupants. Its wavelength is closer to the characteristic vibration wavelengths of the glass, making its propagation more efficient through the vehicle's windows. The accurate modeling of these phenomena requires the coupling of high-frequency computational fluid dynamics (CFD) simulations and vibro-acoustic simulations. CFD simulations must reproduce the creation and propagation of acoustic waves in the airflow around the vehicle. The Lattice-Boltzmann method can be used for this purpose. Vibro-acoustic simulations must allow for coupling between the loading from the airflow, the vibration of the outer skin of the windows, and the propagation of the noise inside the cabin to the occupants' ears. This article presents the approach developped at RENAULT Group, based on Dassault Systèmes' PowerFlow and wave6 software, as well as internal tools. This suite of tools allows for the prediction of aeroacoustic noise inside the cabin and the identification of influential parameters such as the shape of the body elements, mirrors, etc. This data is obtained through the automatic generation of experimental plans. The results allow RENAULT's acousticians to collaborate with designers to obtain the quietest vehicle shape.