Flowfield Analysis of Vortex Interactions During Large Sharp-Edged Gusts

Uncrewed air vehicles in urban environments will have flights during terminal operations that are dominated by strong transient aerodynamics. These vehicles are not only lighter and smaller than traditional rotorcraft and helicopters, but in many instances they may be hybrid configurations with lifting surfaces similar to those of fixed-wing aircraft. These differences require further understanding of the physics of these transient aerodynamics, specifically large-amplitude transverse gusts and the resulting vehicle response, where classic indicial theory is no longer valid. This is crucial to the safety and certification of these air vehicles near buildings and populations. Prior efforts identified that gust responses depart from traditional linear theory when the leading-edge vortex (LEV) forms as a distinct feature and departs from the lifting surface, resulting in flow nonlinearities. This paper expands our understanding of the interactional physics of these nonlinear transverse gusts with flow separation. LEV and trailing-edge vortex (TEV) behavior are correlated, and these vortex interactions are studied to understand the impact on flow separation and subsequent aerodynamic behavior. Larger gust ratios are observed to increase the LEV normal translation, while flow separation is driven by the location and magnitude of the TEV.