Vortex Gust Interaction With a Freely-Flying Rigid Airfoil

This study employs numerical simulations to investigate the interaction between an isolated vortex gust and a freely-flying airfoil at low Reynolds number. The airfoil is modeled as a NACA0012 airfoil capable of passively heaving in response to incoming disturbances, while the vortex is generated by a prescribed uni-directional flapping motion of an upstream 'vortex-generation' airfoil. The simulations examine the effects of vortex rotation, vertical position, and the airfoil angle of attack by measuring the passive heave motion and the lift coefficient of the freely-flying airfoil. The results show that prior to vortex impingement, the airfoil motion is largely insensitive to vortex vertical position and angle of attack and is due primarily to the induced flow of the vortex (upwash or downwash). During the interaction the airfoil experiences a steep change in lift coefficient and continues its heave motion. Once the vortex leaves, the airfoil rebounds back towards its equilibrium position and lift forces decrease, although its final heave position differs from its original location. Variations are seen between angles of attack, with stronger flow separation observed at high angles of attack with clockwise vortex interactions.