Two aspects of porous materials that substantially influence the turbulent boundary layer convecting over them are surface roughness and permeability, and although their individual effects is well documented, their combined action and non-linear interaction are poorly understood. Nevertheless, nature and engineering are replete with examples of such surfaces where both surface roughness and permeability compete. For example porous foams (rough and permeable) have been used to for passive noise control, however, with limited sucess.
This is because noise reduction obtained by Porous materials is not well understood. Previous research has shown noise reduction with porous materials is obtained only for a specific range pore size and thickness; however, the precise values or range is unkown. Therefore, my current research is focused on finding the values for pore thickness and size for which we can expect a reduction in noise.