Vortex Dynamics in Axisymmetric Inlet Over a Plane in a Cross Flow

The formation and evolution of a vortex that forms over a horizontal plane due to the suction into an axisymmetric inlet in the presence of a cross flow over the plane and normal to the inlet is investigated in wind tunnel experiments. In these investigations, the speeds of the cross flow and inlet flow and the height of the plane are independently varied and lead to the identification of a critical range at which the shear layer between the inlet (suction) flow and the cross flow leads to the formation of a columnar vortex over the ground plane that is ingested into the inlet. PIV measurements are used to characterize the critical inlet speed required for the onset of vortex formation and it is shown that this speed increases with the height above the plane and/or with cross flow speed. These measurements are used to assess the vortex characteristic cross section and circulation after the formation as the flow parameters continue to vary. It is also shown that the shear that is needed for the plane-normal vortex can be induced in the absence of a cross flow even when the inlet is far from the ground plane. It is anticipated that understanding the development of these vortices and the dependence of their strength and motion dynamics on the formation conditions will allow for development of methods for controlling their evolution and thereby reduce the adverse effects of their ingestion on propulsion systems.