Near wake hydrodynamics and structural design of a single foil cycloidal rotor in regular waves

We present a hydrodynamic and structural model to design a single foil wave cycloidal rotor in regular waves. The hydrodynamic part considers potential flow and represents the foil as a point vortex. Unsteady effects are accounted for through Theodorsen's function. The structural part utilises beam theory to compute the bending moments and stresses on the foil of the cyclorotor. The validity of the hydrodynamic model is explored with the aid of CFD, and the CFD results are bench marked versus experimental measurements. Results show that the hydrodynamic model estimates the mean radial loading on the foil within 20-25% in attached flow conditions, whilst it is accurate to predict the mean tangential loading only when operating close to stall, at maximum lift conditions. Because the optimal structural operation of the rotor is in attached flow conditions, and close to stall, we utilise the coupled model to design a rotor that operates optimally for a range of different sea conditions. We find that with careful dimensioning of the radius and span, power extraction in regular waves can be optimised, whilst the structural penalty is kept constant at the allowable stress level.