Wake characteristics of a TriFrame of axial-flow hydrokinetic turbines

An effective way to develop arrays of hydrokinetic turbines in river and tidal channels is to arrange them in TriFrame™ 1 configurations where three turbines are mounted together at the apexes of a triangular frame. This TriFrame can serve as a building block for rapidly deploying multi-turbine arrays. The wake structure of a TriFrame of three model turbines is investigated using both numerical simulations and experiments. In the numerical part, we employ large-eddy simulation (LES) with the curvilinear immersed boundary method (CURVIB) for fully resolving the turbine geometry details to simulate intra-turbine wake interactions in the TriFrame configuration. First, the computed results are compared with the experiments in terms of mean flow and turbulence characteristics with overall good agreement. The flow-fields are then analyzed to elucidate the mechanisms of turbine interactions and wake evolution in the TriFrame configuration. We found that the wake of the upstream TriFrame turbine exhibits unique characteristics indicating presence of the Venturi effect as the wake encounters the two downstream turbines. We finally compare the wakes of the TriFrame turbines with that of an isolated single turbine wake to further illustrate how the TriFrame configuration affects the wake characteristics and power production in an array of TriFrames.