Experiments on Supersonic Boundary Layer Laminarization by Means of Foreign-Gas Injection

Abstract

Experimental investigation of the influence of the distributed heavy gas (sulfur hexafluoride, SF6) injection into the near-wall sub-layer of a boundary layer) on the hydrodynamic stability in relation to controlled disturbances of the supersonic flat-plate boundary-layer at free-stream Mach number M = 2 have been performed. It was for the first time in controlled experiments obtained that injection of this foreign gas leads to the boundary-layer stabilization that is manifested in reduction of disturbance amplification rates. Good quantitative agreement of collected experimental data with computations based on the linear stability theory is obtained.