Numerical Study of Cavitation for Horizontal Axis Hydrokinetic Turbine*

Horizontal axis hydrokinetic turbines are numerically studied to assess the deployment and operating conditions for which cavitation may play an important detrimental role to both turbine performances and its structural integrity. For some critical, yet practical conditions, the turbine performances may be dramatically decreased due to cavitation. The effects of cavitation are studied with 3D URANS numerical simulations using the Volume of Fluid approach and the Schnerr-Sauer cavitation model. Two different 3-bladed turbine designs are considered at large and small scales in different inflow conditions and blockage. The turbines differ with their blade profile and chord distribution. The present research is mainly focused on the effects of the cavitation number, tip-speed ratio, confinement level and Reynolds number. These parameters are shown to impact the inception and extent of the region of cavitation which in turn may affect more or less strongly the turbine performances. The presentation also discusses some design choices that can be made to restrain the vapor region, especially near the blade tip where cavitation usually takes place.