Investigations of high-speed boundary layer stabilization by using porous coatings (review)

Activities aimed at studying stabilization of a high-speed boundary layer with the use of porous coatings are reviewed. All types of coatings used in experimental research are considered. It is demonstrated that a porous coating with optimal parameters can stabilize the second mode of disturbances to a large extent and delay the laminar-turbulent transition in a high-speed boundary layer. A review of numerical investigations of porous coatings is presented, and it is shown that special boundary conditions are imposed for porous coating modeling; otherwise, the flow has to be calculated in each pore of the coating. The major part of results obtained on the basis of the linear stability theory and in direct numerical simulations agree well with experimental data. Examples of methods of porous coating optimization and of using promising metamaterials are provided.