Review of research into shock control bumps

Abstract

This paper presents a review of research on shock control bumps (SCBs), a class of flow control device with potential for application to transonic wings. Beginning with a brief review of the origins of the SCB concept, the primary focus is on the more recent studies from the last decade. Results from both experimental and numerical work are considered and the synergy between these two approaches to SCB research is critically explored. It is shown that the aerodynamic performance enhancement potential of SCBs, namely their capacity for drag reduction and delaying the onset of buffet for transonic wings, has been widely demonstrated in the literature, as has the high sensitivity of SCB performance to flow conditions including shock strength and position, and post-shock adverse pressure gradient. These characteristic features of SCBs are relatively well explained in terms of the flow physics that have been observed for different bump geometries. This stems from a number of studies that have focused on the balance of viscous and inviscid flow features and also the mechanism by which finite span SCBs generate streamwise vorticity. It is concluded that our understanding of SCBs is reaching an advanced level of maturity for SCBs in simple configurations and steady flow fields. However, SCB performance in unsteady flow and on swept wings requires further investigation before the concept can be considered a viable candidate for transonic wings. These investigations should adopt a multi-disciplinary approach combining carefully designed experiments and targeted computations. Finally, two concepts for future SCB research are suggested: the adaptive SCB and SCBs in engine intakes.Communicated by A. Hadjadj.

Optimisation of adaptive shock control bumps with structural constraints

“…Fig. 9 illustrates a set of more realistic pressure distributions that a local (SCB-type) device might produce, consistent with previous research [9]. These profiles include inflection points, where the pressure gradient changes sign.…”

“…stream or downstream of its optimal location) have shown that even small variations in shock position, as would accompany minor changes in Mach number or incidence during flight, can significantly impact performance, through the appearance of undesirable expansions, secondary shock systems, and flow separations [9]. Thus, the dilemma facing wing designers is how to exploit the performance-enhancing potential of SCBs over a narrow range of shock positions (operating envelope) without incurring excessive off-design penalties.…”

The Use of Actuated Flexible Plates for Adaptive Shock Control Bumps

“…The effects of continuously changing deflection angles weaken which has been identified previously. 22 The rear leg of the actuated case shown in figure 17 does not decelerate the flow to subsonic conditions immediately. Starting after the crest of the actuated SCB, the main normal shock does not extend beyond the triple point height suggesting a definitive secondary shock structure below the inferred structure in figure 17.…”

Supersonic flow control

“…In continuation to the research on mechanical control techniques, the review by Bruce and Colliss [41], which once again focuses on flow control in transonic regime, primarily looks at a new class of control devices called shock control bumps (SCB). Since the control in this device is based on the generation of a system of weaker compression waves ahead Fig.…”

“…6 Example of micro-ramp with primary vortex pair of the main shock, this type of control was seriously considered for application on the upper surface of the transonic wing and in supersonic flows for intakes. The effectiveness of this control device is based on the two important criteria [41]: (i) their impact on drag at the optimal design (of SCB) and at the optimal design point (of the aerofoil) and (ii) their impact on off-design phenomena such as buffeting. Although both 2-D and 3-D SCB show beneficial flow characteristics, the performance benefit of the SCBs is mainly realized at high values of lift coefficient (C L ) rather than at lower values, where a clean wing scores better [42,43].…”