This paper presents a discussion on the characterisation of the wake of horizontal axis marine current turbines. Understanding the effect devices have on the flow is critical in determining how one device may modify both the performance of and loading experienced by another device in a farm or array. It is the aim of this work to identify and investigate the parameters which govern the wake structure and its recovery to the free-stream velocity profile. An experimental and theoretical investigation of the flow field around small-scale mesh disc rotor simulators is presented. Wake characteristics of the rotor simulators have been measured in the 21m tilting flume at the Chilworth hydraulics laboratory, University of Southampton. The experimental results are at present being used to develop a numerical wake model for Marine Current Energy Converter (MCEC) devices. Based on an industry standard wind turbine wake model, developed by Garrad Hassan over the last 15 years, an eddy-viscosity model is presently being developed to model device wakes.
This work has been conducted as part of a DTI-funded project to develop a tool which will assist in the layout design of arrays, ensuring they are optimally spaced and arranged to achieve the maximum possible energy yield at a given tidal energy site.