Coefficients of heat transfer to the surface in a laminar hypersonic flow (M ∞ = 21) over plane and axisymmetric models with a compression corner are presented. These coefficients are measured by an infrared camera. The parameters varied in the experiments are the angle of the compression corner and the distance to the corner point. Characteristics of the flow with and without separation in the corner configuration are obtained. The measured results are compared with direct numerical simulations performed by solving the full unsteady Navier-Stokes equations. Experiments with controlled streamwise structures inserted into the flow are described. A substantial increase in the maximum values of the heat-transfer coefficient in the region of flow reattachment after developed laminar separation is demonstrated. Key words: hypersonic flow, laminar separation in the compression corner, streamwise structures, heat transfer to the surface.
Introduction.A large amount of theoretical and experimental studies of heat transfer in a supersonic flow in a compression corner is currently available. These activities are important because corner surfaces are essential elements of inlets of supersonic aviation engines, which create conditions for flow compression and for static pressure increase. This portion of the air duct of the engine displays extremely high heat intensity, and its temperature stability is responsible for reliable operation of the aircraft engine as a whole. This problem is particularly relevant in hypersonic flight with several-fold increased stagnation temperatures and, hence, heat fluxes to the surface.One important feature of a hypersonic flow in a compression corner is the emergence of transversal nonuniformity of the flow, which can be enhanced in the field of centrifugal forces generated by variations of the flow direction. Experimental studies of the flow around plane and axisymmetric configurations at moderate hypersonic Mach numbers revealed the emergence of streamwise structures [1, 2] and a significant increase in the maximum values of the heat-transfer coefficient [3]. An apparent reason for these phenomena is the emergence and development of transversal nonuniformity induced by natural roughness of the leading edge of the model. Experimental and numerical studies without modeling transversal nonuniformity were performed for high Mach numbers, in particular, for conditions of a hypersonic viscous shock layer. It should be noted that numerical simulations (with allowance for three-dimensional effects) of hypersonic flows in corner configurations are rather difficult, and numerical algorithms require experimental verification. It seems of interest, therefore, to measure the heat-transfer coefficient in compression corners at high Mach numbers and in the presence of transversal nonuniformity.