A Vortex-Lattice Method for the Prediction of Unsteady Performance of Marine Propellers and Current Turbines

In this paper, the unsteady hydrodynamic analysis of marine propellers and horizontal-axis tidal current turbines is performed by using a vortex lattice method (VLM). A fully unsteady wake alignment algorithm is implemented into the VLM to satisfy the force-free condition on the propeller and turbine wake surfaces. It was found that the position of the trailing wake is very important in predicting the performance of propellers or turbines in steady or unsteady flow. The effects of a non-linear interaction between the inflow and the propeller/turbine blades have been taken into account by using a hybrid viscous/potential flow method, which couples the potential flow solver for the unsteady analysis of the propeller/turbine and a viscous flow solver for the prediction of the viscous flow field around them. The present method is then applied to predict unsteady hydrodynamic performance of a propeller and a horizontal-axis tidal current turbine. The predicted unsteady forces of a propeller subject to an inclined inflow are compared with those from experiments. The hydrodynamic performance of tidal turbine in yawed flow for various yaw angles is investigated. The numerical results are compared with existing experimental data.