Impingement of a Vortex Pair on Static and Dynamic Perturbed Walls

Counter-rotating vortex pair wakes (CRVP) are an unavoidable by-product of aircraft lift generation. Aircraft encountering these wakes can be subjected to unexpected hazardous rolling moments, which can prove fatal. This is especially true in terminal flight phases where there is insufficient altitude to recover. In contrast to terrestrial landings, Naval aircraft in terminal flight phases must also contend with approaches above a highly dynamic oceanic free surface. Understanding the behavior of these wakes near the ground is therefore of peak importance for aircraft operations and safety. This investigation uses a towed delta wing to generate a spatially-evolving CRVP that descends towards the ground plane under its own self-induced velocity. A static perturbed wall is placed at the ground, representative of a perturbed oceanic surface. Laser-induced fluorescence and particle-image velocimetry (PIV) measurements are taken to assess the vortex-wall interaction and quantify the rate of CRVP decay. The spatially-evolving CRVP comprises of both axial and circumferential flows, and approaches the ground plane at an angle. The inclined vortex pair produces three-dimensional secondary vortex structures at the wall, increasing the decay rate of the primary CRVP. Preliminary results show that the interaction of the vortex pair with the dynamic perturbed wall yields highly time-dependent secondary vortex structures.