Inflow-Velocity and Rotational Effects on Revolving and Translating Wings

Abstract

An aspect ratio 9.5 rectangular wing is articulated in revolving and translating motions at a 45-degree angle of incidence and Reynolds number Re = O(300). The effects of rotational (Coriolis and centripetal) accelerations and relative inflow velocity profile are independently investigated. For the range of displacements studied (180 deg. rotation and corresponding translational displacement) a stably attached leading-edge vortex (LEV) is observed when rotational accelerations and/or a linearly-varying inflow velocity profile is present; however, the inflow velocity profile has a stronger effect on stability of the LEV. LEV vorticity magnitude and lift are significantly augmented when both factors are included (i.e. the full revolving wing case). Vorticity transport analyses are conducted in a planar control region two chords from the axis of rotation, where three-dimensional vorticity transport is shown to be important in mitigating LEV growth, and at an equivalent distance from the wing root in the translating case. The fully revolving wing case exhibits a substantially larger leading-edge shear-layer vorticity flux than the other cases, whereas Coriolis tilting makes little contribution to regulation of LEV strength. A correlation is found between the spanwise convective flux and tilting flux contributions in all cases. Decomposition of the spanwise convective flux term demonstrates that the two phenomena are kinematically linked and yields a significantly simplified vorticity transport equation with a single term consolidating the three-dimensional transport fluxes, thus providing new physical interpretation of vorticity transport in leading-edge vortices.