Characterization of vorticity transport mechanisms during the transient phase of a rotating wing

Studies have demonstrated that in the quasi-steady phase, spanwise convection of vorticity and the Coriolis tilting, among others, lead to the transport of vorticity from the leading-edge vortex (LEV), which mediates the LEV. However, understanding the vorticity transport mechanisms in the transient phase is equally important and has not yet received much attention. This study aims to explore the effect of wing acceleration on the mechanisms that regulate the development of LEV on a rotating wing. As such, the flow field over the wing was experimentally quantified using Rotating Three-Dimensional Velocimetry (R3DV) technique under varying wing acceleration and Reynolds numbers. Vorticity transport analysis in the rotating frame will be used to quantify the in-plane and out-of-plane fluxes of vorticity. Initial findings suggest that when the acceleration is low, the surface diffusive flux (due to secondary vorticity) annihilates the excess vorticity transported by the shear layer, thus mediating the growth of the LEV. At higher acceleration rates, a lag in the production of secondary vorticity is observed, leading to a higher amount of vorticity transfer from the shear layer to the LEV. In this study, along with these in-plane fluxes, the contribution of out-of-plane fluxes to the vorticity transport from the LEV will also be investigated.