Three dimensional shock induced separated flow

Supersonic flow over 3-dimensional bodies protruding out of the turbulent boundary layer was investigated by means of experiments and numerical computations. A parametric study was performed by varying the shape and dimensions of the protuberance, as well as the freestream Mach number (1.5, 2, 2.5, 2.89, 3.5). Surface streak line visualization, surface pressure measurements, and time-resolved schlieren visualization were employed along with RANS computations to elicit the complex flow features such as separation line, shock pattern, and the horseshoe vortex which greatly influences the flow dynamics in the separated region. The rise in surface pressure at mid-span due to separation (plateau pressure) was dependent only on the incoming flow parameters, and independent of protuberance geometry. The 2-dimensional free interaction theory, applied for normal shock-induced separation, closely predicts the mid-span plateau pressure. Although protuberances are of varying shapes and dimensions, the inviscid bowshock (obtained from Euler computations) provided generalized scales, whose effects on shock boundary layer interactions are analyzed. The radius of curvature of the inviscid shock on the wall plane at the nose, which is theoretically related to the local second derivative (along the shock)of pressure jump, was found to be a determining parameter of mid-span separation length (????sep). Since the spanwise distance of the sonic point on the inviscid shock was found to be strongly correlated to its nose radius of curvature, it follows that the strong portion of the inviscid bowshock fixes the mid-span separation location. These observations concerning mid-span plateau pressure, and the role of strong shock portion in fixing mid-span separation, suggest that the ????sep shall be predicted from a modification of the scaling laws for the length of plateau pressure region in 2-dimensional shock boundary layer interaction, with the inclusion of spanwise relieving effect. A correlation is obtained relating the ????sep with various incoming flow parameters and inviscid shock nose radius. The mid-span vortex core position was found to be linearly related to the ????sep. The radius of curvature of the separation shock is, however, found to be influenced by the entire inviscid shock, including the weak portion.