FTLE structure of the unsteady flow around accelerated non-slender swept wings

Previous experiments have shown that for a 45° sweep delta wing with an NACA 0012 cross section, the flow around the wing is fully separated by 25° in steady translation. To study the influence of an axial wing acceleration on the flow structure, time-resolved planar PIV and surface pressure measurement were conducted at angles of attack of 20° and 30°, with axial acceleration 1≤g*≤6, where g*=s_gust/c is the distance over which the acceleration takes place, normalized by the chord. Distance traveled is denoted by s*=s/c. Finite-time Lyapunov exponent (FTLE) analysis, combined with instantaneous pressure and velocity profiles, showed that axial acceleration contributes to flow reattachment under certain conditions. Future work will also study vertical accelerations, and those results combined with the axial acceleration results may provide a foundation to develop methods for predicting forces and moments on wings in highly unsteady environments.