Investigation of wave–current interaction for a tidal current turbine

Abstract

Due to linear wave theory limitations, higher-order theories have been coupled with the Blade Element Momentum (BEM) model to predict the time behavior of the dynamic loading on the combined wave–current field. Second-order, third-order approximations and fifth-order stokes theory have been used to check their effects on the predicted wave kinematics and on the resulting dynamic loadings. To overcome the problem of linear superposition method, a wave–current interaction model was implemented. A significant change in the wave length and wave height was obtained, whereas a negligible change was observed for the current velocity and water depth. By implementing a wave–current interaction model for a wave train and inflow current in the same direction of the wave propagation, the loading ranges of blade root bending moments significantly decreased, whereas their wave lengths increased. Furthermore, a parametric study was performed through increasing the wave height and current velocity to reveal their effects on the dynamic loadings with and without considering the wave–current interaction. Big differences were obtained between the maximum predicted loads for cases with and without interaction, which would help in the proper selection of tidal current turbine’s structural design.