Experimental investigation on the role of boundary layers around a supersonic cylinder in rarefied flows

This paper describes the evolution of the boundary layer around a cylinder and its contribution to the drag force in supersonic rarefied flows. Experiments are performed at two different Mach numbers in the MARHy wind tunnel (formerly known as SR3). Shock-wave visualizations, aerodynamic force measurements and static wall-pressure measurement are compared with the evolution of the boundary-layer thickness and the skin-friction-drag coefficient for a large range of laminar Reynolds numbers and Knudsen numbers in the slip regime. The skin-friction-drag coefficient, together with the thickness of the boundary layer measured near the stagnation point are found to scale with the rarefaction coefficient defined by Tsien [1].