In order to capture significant energy,hydrokinetic turbines need to be built in large arrays within regions such as rivers,man-made channels or tidal straits where the local bathmetry focuses the flow.The layout of these arrays of turbines can significantly change the amount of energy captured from the flow.The Power output expected form specific array must be predicted with high level of certainty to minimize the risks taken by developers and stake holders.These predictions can be achived through experimental studies on small scale deployments in laborataries.For instance simple farm models composed of a few turbines have been studies in a water channel[3][4].It is however expensive to perform such experimental works to study the device parameters in large scale turbine arrays and in real environmental conditions.On the other hand,numerical modelling simulations lower the risk and cost for power output prediction,although there remains a need to validate the results against measured data.
The explicit modelling of turbine blades can be achived through the (URANS) approach,As demonstrated by Zanatte[5] for Darrieus type turbines,this approach is useful for evaluating,in the immediate vicinity of turbines,the complex flow conditions including high levels of turbulence,shear and variable flow directions.However,its cost is high even for an isolated turbine and such a high fidelity numerical modelling is not applicable to describe turbines at the farm array scale.
Serveral fast calculation models, base on simplified models of turbines,have thus been presented to predict turbine performance within an array.