Analysis of Flowfield Vortex Interactions of Nonlinear Sharp-Edged Transverse Gusts

Abstract

Unmanned and urban 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 fixed-wing aircraft. These difference require further understanding the physics of these transient aerodynamics, specifically large amplitude transverse gusts and the resulting vehicle response. This is crucial to the successful development and certification of safe air vehicles near buildings and populations. Prior efforts identified that gust responses depart from traditional linear theory when the leading edge vortex first forms as a distinct feature and breaks away from the wing, resulting in flow nonlinearities. This paper expands understanding of the interactional physics of these nonlinear transverse gusts with flow separation. Leading edge vortex (LEV) behavior is correlated with trailing edge vortex (TEV), and the vortex interactions are studied to understand their effect on flow separation and subsequent aerodynamic behavior. Higher gust ratios are observed to increase the normal translation leading edge vortex, while separation is driven by location and magnitude of the TEV behavior.