On the Detachment of a Leading Edge Cavitation

In the present paper we present an experimental investigation of the onset and detachment of leading edge cavitation. Tests are conducted in the LMH high speed cavitation tunnel on a 2-D Naca0009 hydrofoil having 100 mm chord length. Both Particle Image Velocimetry and flow visualisation are conducted for different test conditions. At low incidence angles, in the case of non cavitating flow, the velocity field do not show any laminar separation of the boundary layer in the suction side of the hydrofoil. In the case of well developed attached cavitation, we have clearly shown that the distance between the separation and the cavity detachment points is less than our PIV spatial resolution (5.10 m). We have also shown through flow visualisation that an increase of the incidence angle of the hydrofoil leads to an unstable transition from bubble cavitation to attached cavitation. These observations let us believe that, in our specific experimental set-up, the flow separation is generated during the transition process from bubble to attached cavitation with a significant influence of the surface roughness and physical properties of the hydrofoil material as well as the wall pressure distribution along the suction side of hydrofoil.