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., [14].

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., [20], and also [21]. 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 [22]-[24], and especially [25]. 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 [26]. 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.

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