A theory of vortex-surface collisions

Abstract

The interaction of vortices with solid surfaces occurs in many different situations including, but not limited to tornadoes, propeller wakes, flows over swept wings and missile forebodies, turbomachinery flows, bladevortex interactions and tip vortex-surface interactions on helicopters. Often, parts of a system must operate within such flows and thus encounter these vortices. In the present paper we discuss the nature of a particular subset of interactions called "collisions". A "collision" is characterized by the fact that the core of the vortex is permanently altered; usually the core is locally destroyed. The focus is on fully three-dimensional collisions although two-dimensional collisions are discussed as well. Examples of collisions in helicopter aerodynamics and turbomachinery flows are discussed and the dynamics of the vortex core during a collision process are illustrated for a 90° collision.

Propeller and inflow vortex interaction: vortex response and impact on the propeller performance

“…For the counter-rotating open rotors (CROR), the tip vortex shed form the front rotor may impinge onto the aft rotor, as the two rotors have the same radius [2] or as the rotors operate at an angle of attack [3]. For a turbofan engine, besides the ground vortex impingement [4], the blade vortex interaction can also occur between the rotor and stator [5,6]: the vortex shed from the rotor collides with the downstream stator [5]; the secondary vortex in the stator wake impinges on the rotor [6]. Blade-vortex interaction can also be observed when the vortex shed from the main rotor of helicopter collides with the tail rotor [7], as shown on the right-hand side of Fig.…”