Triglobal resolvent analysis of finite-aspect-ratio swept wing wakes*

We perform triglobal resolvent analysis for laminar flows over finite-aspect-ratio swept wings. Base flows are obtained from direct numerical simulations at a chord-based Reynolds number 400 and a freestream Mach number 0.1 over NACA 0015 wings with an aspect ratio 4 at different post-stall angles of attack and angles of sweep. For the unswept wings, the wake is dominated by the interaction of mid-span vortex shedding, tip vortex and an interaction zone. As we increase the sweep angle, the wake oscillations are stabilized and finger-like structures appear. Through resolvent analysis we are able to identify these phenomena through mode switching over varied frequencies. For wings with sweep angles less than 15 degrees, the mid-span shedding structures are the primary response modes at the vortex shedding frequency. As frequency increases, these modes become secondary while the primary modes develop from the wing tip. For higher sweep angles, the tip modes dominate the response mechanisms for all frequencies. These studies provide fundamental insights on the complex wake dynamics behind finite-aspect-ratio swept wings.