Marine and hydro-kinetic (MHK) energy hold promise to become significant contributor towards sustainable energy generation. Despite the promise, commercialization of MHK energy technologies is still in the development stage. While many simplified models for MHK site resource-assessment exist, more research is needed to enable efficient energy extraction from identified MHK sites. A marine energy company named Verdant Power Inc. was granted first federal license to install up to 30 axial hydrokinetic turbines in the East River in New York City under what came to be known as Roosevelt Island Tidal Energy (RITE) project. Therefore, in this study we investigate issues of relevance to post-site-identification stage for a real-life tidal energy project, the RITE project, using high-fidelity numerical simulations. An effective way to develop arrays of hydrokinetic turbines in river and tidal channels is to arrange them in TriFrame configurations where three turbines are mounted together at the apexes of a triangular frame. The TriFrames serve as the building block for rapidly deploying multi-turbine arrays. The wake structure of a TriFrame of three model turbines is investigated. We employ large-eddy simulation (LES) with the curvilinear immersed boundary method (CURVIB) for fully resolving the turbine geometry details to simulate turbine-turbine wake interactions in the TriFrame configuration. First, the computed results are compared with experiments in terms of mean flow and turbulence characteristics with overall good agreement with bed-flume experiments. 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. Lastly, we propose a large eddy simulation (LES)-based framework to investigate the site-specific flow dynamics past MHK arrays in a real-life marine environment. To this end, the new generation unstructured Cartesian flow solver, coupled with a sharp interface immersed boundary method for 3D incompressible flows, is used. Optimized data-structures and efficient algorithms were developed to enable faster simulation on high-resolution grids. Multi-resolution simulations on locally refined grids are then employed to model the flow in a section of the East River with detailed river bathymetry and inset turbines at field scale. The results are analyzed in terms of the wake recovery and overall wake dynamics in the array. Comparison with the baseline flow in the East River reveal the effects of tidal array installation.
University of Minnesota Ph.D. dissertation. April 2017. Major: Mechanical Engineering. Advisors: Fotis Sotiropoulos, Lian Shen. 1 computer file (PDF); x, 148 pages.
Multi-resolution Modeling and Simulation of Marine Hydrokinetic Turbine Arrays at Site Scale.
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