Viscous-Flow Calculations On An Axial Marine Current Turbine

In this paper, the flow over a marine current turbine is studied. As a test case, the benchmark turbine published in [1, 2] is selected. A bibliography review shows a variety of numerical methods applied to this specific turbine, of which a viscous-flow RANS approach seems to be the best suitable for simulations over a broad range of inflow conditions. Therefore, MARIN’s RANS solver ReFRESCO is used to study the flow over this turbine. ReFRESCO results show a good agreement with the experiments, the calculated results and associated uncertainties overlapping the model-tests results. A numerical procedure is followed to estimate these calculation uncertainties, including an estimation for the numerical, domain and geometrical uncertainties. The flow-field analysis reveals significant viscous effects. Large separation zones at the suction side of the blade are seen in the model-scale results. At model scale, the turbulence level indicates that the turbine is operating in the transitional regime between laminar and turbulent flow, leading to early flow separation. Calculations at full scale show a large scale effect. The separation zones present at model scale are significantly smaller at full scale, resulting in a higher power production and axial loading. This is explained by the fully-turbulent boundary layer.