Quantifying the Impacts of the Angle of Attack on the Morphology of Atmospheric von Kármán Vortex Streets

A mesoscale model is used to systematically investigate how the incoming flow incidence angle affects the development of atmospheric von Kármán vortex streets for non-axisymmetric islands. The analysis is focused on an event observed on the leeward side of Guadalupe Island. By keeping the synoptic conditions the same, several simulations are performed for rotated orientations of the island topography, which correspond to a change in the angle of attack (AoA) relative to the upstream flow. The asymmetry of the vortex shedding and the role of the leading and trailing edge are in line with what was observed in laboratory von Kármán vortex streets past a flat plate. The eddies become larger with increasing AoA while the shedding frequency decreases, and the asymmetry between cyclonic and anticyclonic eddies weakens. Cyclonic vortices are more developed and stronger under typical conditions when they are shed from the trailing edge. We also demonstrate that the wake asymmetry is fundamentally between trailing-edge and leading-edge eddies rather than between cyclonic and anticyclonic eddies.