Mechanism of stabilization of porous coatings on unstable supersonic mode in hypersonic boundary layers

This study clarifies the fundamental mechanism by which porous coatings suppress supersonic mode instability in hypersonic boundary layer (BL) using Doak's momentum potential theory. The independent energy budget equations for vortical, acoustic, and thermal components of instabilities are derived. Data from direct numerical simulations Mach 6.0 flat plate flows on a solid wall then analyzed. By decomposing density into components, source terms fluxes studied based their corresponding corollaries. results demonstrate role different generation transport total fluctuation enthalpy (TFE) way is transferred between components. In case wall, oscillating disturbance BL consists acoustic vortical Near critical layer, positive component primary producers fluxes. Then, TFE transported outward component, leads to “sound radiation” mode. coating, near surface suppressed significantly. Less thus less transformed energy. Acoustic eventually exhausted due loss TFE, disappears coating.