In this paper, we describe developments of the AMAZON-3D numerical wave tank (NWT) for a study of wave loading on a wave energy converter (WEC) device in heave motion. The NWT, based on a two fluid free surface capturing and Cartesian cut cell method, is being developed for the simulation of wave loadings on a Manchester Bobber WEC device under regular wave conditions with a view ultimately to facilitating a study of the behaviour of such devices in extreme wave conditions. The method has been validated by comparison with experimental data for various cases including water entry of a rigid wedge and cases involving focused waves. Results include free surface elevations, the vertical displacement of the body, vertical velocity and calculations of heave force for a typical Bobber-type geometry.
The design of a wave energy converter, ship or other floating structure requires due consideration of its operation and survivability in a hostile environment. Both the motion of the free surface and the geometry of the body or structure can be complicated in practical cases. For example, the Manchester Bobber, designed by project partners at the University of Manchester in the UK, is a novel heaving point absorber device comprising a float with a hemispherical base generating oscillatory shaft motion which is converted to unidirectional rotation through a freewheel/clutch which in turn drives an electricity generator. The Bobber represents a generic class of floating buoy device that involving unique combinations of the object motion and incident wave conditions. In order to assess the design and performance of the Bobber, proper specification of a set of input conditions and a full set of flow variables is needed, e.g. pressure and velocity field, as well as integrated effects like forces and response which are usually the output parameters from physical experiments or CFD codes.
