Computational study of shock-buffet on 3D wings

The paper presents a computational study of the transonic shock-buffet flow instability phenomenon on three-dimensional wings. Reynolds-averaged Navier-Stokes simulations were conducted on three wing configurations, all based on the RA16SC1 airfoil, at shock-buffet flow conditions. The simulated configurations include Infinite-straight, Infinite-swept and Finite-swept 3D wing models of several sweep angles and span lengths. Based on the results, the effects of 3D flow, wing-sweep and span-length on the shock-buffet characteristics are identified. For small wing sweep angles the fundamental shock-buffet instability mechanism remains similar to the 2D mechanism, which is characterized mainly by chordwise shock oscillations. For moderate sweep angles, a phenomenon of lateral pressure disturbance propagation is observed. This phenomenon is essentially different from the 2D shock-buffet mechanism, yet results in oscillations of the sectional aerodynamic coefficients. The paper presents and discusses both phenomena, and suggests a connection between them. For high wing sweep angles the wing is stalled and shock-buffet is eliminated. For low aspect-ratio wings, the flow is dominated by tip vortices, and shock-buffet is eliminated. For high aspect-ratio wings, wingtip effects are minor and limited to the tip region. For intermediate aspect-ratio cases, tip vortices and shock-buffet interaction results in irregular shock oscillations.