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° angle of incidence and Reynolds number Re=O(300). The effects of rotational (Coriolis and centripetal) accelerations and relative inflow velocity profile on vorticity transport within the leading-edge vortex (LEV) system are independently investigated. For the range of displacements studied (180° 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 LEV stability is typically observed on revolving wings at high incidence and at an equivalent spanwise position 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, together, define a new out-of-plane convective flux term that captures the essence of the spanwise convective flux. The role of this term and the effect of rotational accelerations on it are examined.