ROTOR WAKE MODIFICATIONS IN HOVER USING UNSTEADY SPANWISE BLOWING

A Computational Fluid Dynamics (CFD) study investigating the effects of unsteady spanwise rotor blade tip blowing on the formation and evolution mechanisms of blade tip vortices shed during hover is presented in this paper. The specific blowing configuration consists of a single jet sheet with modulated mass flow rate controlled through slot area variation, ejected tangentially over a rounded blade tip cap. By using the beneficial Coanda effect of jet attachment to the curved wall of the blade tip cap a downward deflection of the jet sheet direction is obtained. As a consequence the location and formation of the tip vortices are modified in a time dependent manner with reference to a baseline, no-blowing case investigated for the same rotor and flight conditions.