Comparative study of the cavitation resistance of the traditional and high-lift hydrofoils for hydrokinetic application

Abstract

The cavitation phenomena should be considered during the design of hydrokinetic turbines due to cavitation could cause surface erosion, mechanical vibrations, undesirable noise and efficiency reduction in the energy transformation. Therefore, the aim of this work is to conduct a numerical comparison of the cavitation resistance of 3 hydrofoils (NACA0015, Eppler420 and S822) with the purpose of selecting the best foil for the blade cross-section design. For each hydrofoil, the traditional and the high-lift configurations were evaluated. The hydrodynamic factors, including the lift and the drag (CL and CD, respectively) coefficients were determined by using JavaFoil software for several angles of attack (α). Additionally, for the computational fluid dynamics (CFD) study in ANSYs Fluent software, the SST and the Schnerr and Sauer turbulence and cavitation models were respectively utilized to validate the values of CL and CD, and to calculate the pressure coefficient (CP). The values of CP were compared with the cavitation number (σ) for identifying cavitation on the blade and comparing the cavitation resistance of the hydrofoils studied. The methods used and the numerical results obtained were subsequently analyzed and validated using relevant experimental values available in the literature for the NACA0015 hydrofoil. CFD simulations revealed that the NACA0015 traditional hydrofoil and the high-lift configuration of the Eppler420 hydrofoil have the best resistance to cavitation inception in comparison with the traditional hydrofoils and the high-lift configurations studied, respectively.