Influence of the Plate Leading-Edge Shape and Thickness on the Boundary Layer Laminar-Turbulent Transition in Hypersonic Flow

The results of an experimental study on the laminar-turbulent transition in the boundary layer on a blunted plate with a leading edge of various shapes and thicknesses at freestream Mach number M∞ = 5 and unit Reynolds numbers Re1 from 1.5 to 9 × 107 m-1 are presented. The Reynolds number Reb, based on the leading edge thickness b, was varied from 0 to 2 × 106. The following leading edge shapes were studied: cylinder, flat face, ellipse, and smoothened cylinder. In general, it was shown that for Reb < 0.5 × 105, the leading edge shape did not affect the transition location. For higher values of Reb, variations of the leading-edge shape significantly changed the transition location. For all of the shapes considered, a transition reversal was observed. It was shown that the length of the laminar run on a flat plate could be increased by a rational choice of the bluntness shape and thickness.