Micro-PIV and ELDV wind tunnel investigations of the laminar separation bubble above a helicopter blade tip

Abstract

Studies of the boundary layer profile and of the characteristics of the flow velocity distribution close to the leading edge of a helicopter blade profile were conducted using the embedded laser doppler velocimetry (ELDV) and stereo-PIV. The relatively small scales of flow structures leading to dynamic stall, motivated an additional 2C-PIV study in which the flow field has been measured with a relatively high spatial resolution. The feasibility of PIV measurements utilizing a mirror telescope in a wind tunnel has been demonstrated successfully. The spatial resolution of approximately 50 (my)m allowed a judgment on the choice of turbulence models and damping coefficients for the improvement of CFD predictions.