Fluid dynamic performance of a vertical axis turbine for tidal currents

This paper is concerned with the study of a novel design of turbine for tidal currents or fast-flowing streams, called the ‘Hunter Turbine’. The turbine consists of several flapping blades that are hinged on a revolving drum. Flow visualization experiments on a small model were conducted to provide some basic rules from which the movement of every flapping blade at every drum position could be determined. Two-dimensional quasi-steady CFD was then used to obtain detailed information about the flow field, including pressure and velocity contours, and the pressure distribution on the surface of the blades. It was found that the Hunter Turbine gives very satisfactory performance over a restricted range of flow coefficient. Under these conditions, the kinetic energy of the incident flow can be effectively transferred into the movement of the rotor, so that the average power coefficient (based on the projected area with an open blade) reaches a value of 0.19. Using the CFD results, a polynomial function is fitted to the dependence of an effective force coefficient for all blades on the rotational angle and the flow coefficient. The net forces acting on the surfaces of the blades can thus be interpolated between the calculated data points.