Vortex Surface Collisions

Abstract : Many flows of practical interest contain discrete vortices. These include tornadoes, propeller wakes, and flows over swept wings and missile forebodies. The encounter of a vortex with a solid body is always a complex event involving very large gradients of pressure and velocity. We consider the problem in which a rotor-tip vortex with a helicopter airframe. The primary objective of this work is to describe both experimentally and computationally the interaction when the vortex collides directly with the airframe in the sense that at some point the flow in the vortex core must be altered to accommodate the presence of the airframe. The pressure field caused by the collision is also described. The dominant physics of the collision process may be described by inviscid flow theory and it is the component directed along the tip-vortex axis, termed the axial flow, which is the major cause of the collision.