A Perspective on Transonic Buffet over an Unswept Finite Wing

Transonic buffet is a well-known aerodynamic instability of shock/boundary-layer interaction in the transonic regime for aircraft. So far, this phenomenon has typically been investigated by modal and correlation analyses. Here, we present a perspective on low-frequency unsteadiness, of the order of [Formula: see text], in transonic buffet, using results from temporal evolution of skin friction lines and correlation analysis on the surface of Benchmark Supercritical Wing (BSCW) with an aspect ratio [Formula: see text][Formula: see text]. Skin friction lines and critical point theory are well established to describe three-dimensional separated flows based on critical points—nodes, foci, and saddles. Dynamics of these critical points are found in a certain topology in separation regions for different angles of attack, Mach 0.85, and Reynolds number [Formula: see text]. The topology of critical points consists of pairs of contrarotating unstable foci that contribute to the mechanism of formation and propagation of buffet cells—pockets of shock foot oscillations. The dynamic nature of these critical points changes the pressure distribution on the surface, which is reflected as wave propagation in correlation plots.