Rapid expansion of a supersonic boundary layer and its application to the near wake.

Abstract

This paper, based on research done for the Army's Nike X Missile Defense Project, investigates the inviscid behavior of a supersonic vortical flow undergoing a rapid expansion. The origin, character, and strength of the reflected waves produced by the presence of entropy gradients are examined in detail. This work, which is of obvious interest for vortical flows produced by curved bow shock waves, also provides fundamental insights into the role that a supersonic boundary layer plays in a rapid expansion. For weak expansion fans, 6 < 10°, analytical results are obtained which give the variation of flow properties along centered Mach waves in a rotational expansion. For large angle expansions, rotational characteristic solutions are presented for representative laminar and turbulent boundary-layer shear profiles. It is shown also that the method of rotational characteristics is a valuable means of analyzing the detailed behavior of freshly separated flows, e.g., the formation of the separation shock wave and the experimentally observed structure of the free shear layer in the base flow problem.