Shock/Boundary-Layer Interaction Phenomena
We summarize under this title several phenomena which are of interest in hypersonic flight vehicle design. These phenomena can be found for instance:
— at wings, Fig. 6.4, or stabilizers,
— at a the cowl lip of an inlet, Fig. 6.6,
— at the struts of a scramjet, Fig. 6.7,
— at a control surface, in two dimensions this is a ramp, Fig. 6.1 d) or ahead of a canopy (canopy shock),
— on ramps of the external part of the inlet, Fig. 6.5,
— in the internal part of an inlet (oblique shock reflections), e. g., the shock – train in Fig. 6.5, or in a scramjet, Fig. 6.7,
— at the side walls of the internal part of an inlet, or a scramjet (glancing interaction),
— in the longitudinal corners of the internal part of an inlet, or a scramjet (corner flow),
— at the (flush) nozzle of a reaction-control system, see, e. g., .
Shock/boundary-layer interaction phenomena can occur combined with local separation, but can also be connected with global separation. An example for the latter are cross-flow shocks in the leeward-side flow field of a body at large angle of attack, see, e. g., Fig. 3.20.
Interaction phenomena reduce the effectiveness of control surfaces and inlets by thickening of the boundary layer or by causing flow separation. Glancing shocks induce longitudinal vortex separation, oblique reflecting shocks can result in a Mach reflection, see, e. g., , and also . In the attachment region usually an increase of the heat flux in the gas at the wall occurs. Moreover also very large and very concentrated heat flux and pressure peaks can be found locally. The interaction can support laminar-turbulent transition and can induce flow unsteadiness.
We do not discuss here all the mentioned phenomena, and refer instead the reader to the overviews -, and especially . We concentrate on ramp-type (Fig. 6.1 d)) and on nose/leading-edge-type (Figs. 6.4 and 6.6) interactions. These are Edney-type VI (and V), and Edney type III and IV interactions, respectively.
Shock/shock interaction with the associated boundary-layer interaction probably was the first time observed on the pylon of a ramjet engine that was carried by a X-15. At FFA in Sweden B. Edney was prompted by this event to make his by now classical investigations of the phenomenon . He identified and studied experimentally six interaction types, the type IV interaction, see Fig. 9.15 in Sub-Section 9.2.2, being the most severe one.