Effusion Cooling and Flow Tripping in Laminar Supersonic Boundary-Layer Flow

Effusion cooling of a laminar flat-plate boundary-layer flow at Mach 2.7 is investigated using direct numerical simulations. Air is employed as hot and cooling gas and is blown in the wall-normal direction through discrete orifices into the boundary layer to generate a cooling film. In the present investigations, the inclusion of the flow in the blowing pipes enables a comparison with modeled blowing where the coolant mass flux and temperature are prescribed in the respective areas at the wall. Attention is turned to 1) the blowing through multiple rows of holes, under the assumption of a fixed plenum pressure for all pipes; 2) the temperature modeling, which plays an important role when the cooling gas and wall temperature differ; and 3) the flow tripping to turbulence by the blowing. It is demonstrated that simple modeling fails for narrow hole spacing, which lowers (together with the pipe/main-flow interaction) the critical blowing ratio for flow tripping.