Investigating lateral porosity effect on air pumping noise from connected road cavities with CFD simulations

Several mechanisms induced by the tyre/road interaction contribute to the generation of rolling noise. The road texture has a significant role in this process, together with the possible porosity of the road pavement. The latter may influence the noise sources in the high frequency range in which air pumping is supposed to contribute. Even on dense road surfaces with no vertical porosity, possible air flow allowed by the road texture in the contact patch is equivalent to the effect of a so-called 'lateral' porosity which is reckoned to have an influence on the source strength. In this paper, the effect of this lateral porosity is studied with a modelling approach using Computational Fluid Dynamics (CFD). This approach allows the highlighting of some phenomena occurring in the contact patch such as air compression due to the tyre rolling process or air drainage. Simulations are carried out for a smooth tyre and road textures made of more or less connected cavities. A parametric study is presented in the case of a 2D academic configuration to show the influence of air flow resistance in the contact zone on air pumping noise. Finally, air pumping mechanism is simulated for a 3D configuration.