Tyre/road noise: A piston approach for CFD modeling of air volume variation in a cylindrical road cavity

Abstract This paper deals with air volume variation in a road cavity during the rolling of a slick tyre leading to air-pumping. A numerical model was developed based on Computational Fluid Dynamics (CFD), coupled with a function representing the volume variation due to the tyre tread penetration inside the cavity. A simplified method based on an equivalent piston-like movement of the cavity bottom is derived from a tyre/road contact model and validated by comparison with a membrane approach. This method was used to conduct a parametric study to assess the influence of volume variation and rolling speed on dynamic air pressures and associated signal energy levels. It was found that the overpressure reached during the contact increases with the volume variation of the cavity and with the rolling speed. The pressure signal energy level emitted at the leading edge increases with the velocity but is negligibly influenced by the volume variation. However, the signal energy level at the trailing edge increases with the volume variation without being influenced by the rolling speed. Furthermore, the speed exponent linking the signal energy level with rolling speed was found to be less than 4 at the leading and trailing edges which is consistent with previous work.