Analysis of scale effects on tide turbine cavitation

Cavitation can appear on the rotating blades in water. Facilities built for testing models of cavitating marine propellers and methods developed for extrapolation of their test results to full-scale conditions has been frequently used for tide turbines. However, a significant difference in the scale effects on cavitation for propellers and tide turbines exists. Flows on turbine blades takes place at much smaller Reynolds numbers, whereas their blades are much thicker and laminar-turbulent transition more significantly impacts their cavitation inception. Variation of submergence of the turbine blade sections during their rotation has the greater impact on cavitation inception and growth than the inflow non-uniformity because of the greater impact of buoyancy of cavities. On the other hand, there are no regular spirals of cavitating vortices downstream of tide turbines due to this variation.Here scale effects on tide turbine cavitation inception are analyzed using a simplified model of the flow. The substantial effects of transition in the boundary layer and of the axis submergence on full-scale turbine cavitation are manifested. Estimations of pressure pulsations caused by periodical collapse of cavities on blades is provided and the submergence impact on frequencies of flow-induced noise is shown. Also, biofouling impact on cavitation considered.