SBLI control for wings and inlets

Abstract

The application of flow control to shock wave / boundary layer interactions (SBLIs) has been widely studied in recent decades. Two important practical applications for shock control technology are transonic wings (Fig. 1) and supersonic engine inlets (Fig. 2). In both cases the overall performance is significantly affected by shock wave / boundary layer interactions and it is hoped that flow control can provide considerable benefits.Current methods of SBLI control can be classed into two groups: Shock control and boundary layer control. The latter type modifies the boundary layer ahead of a shock interaction to prevent or delay shock-induced separation. This class of control is particularly suitable in applications where strong shock waves are encountered and flow separation is the prime performance degradation mechanism. Supersonic engine inlets fall into this category. Shock control, on the other hand, attempts to modify the structure of a SBLI with the aim to reduce the overall stagnation pressure loss. This type of control is more relevant to transonic airfoils which are generally operated far from shock-induced separation. To some extent, the two types of control have contradictory effects; boundary layer control often tends to increase stagnation pressure losses through the shock, while shock control often causes a degradation of the boundary layer. This paper presents a brief overview of the current state of the art of flow control for SBLIs.