Large eddy simulation of tidal turbines

Understanding of hydrodynamics involved in the flow around tidalturbines is essential to enhance their performance and resilience, asthey are designed to operate in harsh marine environments. Dur-ing their lifespan, they are subjected to high velocities with largelevels of turbulence that demand their design to be greatly opti-mised. Experimental tests have provided valuable information aboutthe performance of tidal stream devices but these are often conductedin constricted flumes featuring turbulent flow conditions different tothose found at deployment sites. Additionally, measuring velocitiesat prospective sites is costly and often difficult. Numerical methods arise as a tool to be used complementary to theexperiments in investigations of tidal stream turbines. In this the-sis, a high-fidelity large-eddy simulation computational approach isadopted and includes the immersed boundary method for body repre-sentation, due to its ability to deal with complex moving geometries.The combination of these numerical methods offers a great balance between computational resources and accuracy. The approach is ap-plied and validated with simulations of vertical and horizontal axistidal turbines, among other challenging cases such as a pitching air-foil. An extensive validation of predicted hydrodynamics, wake de-veloped downstream of the devices or structural loadings, outlinesthe accuracy of the proposed computational approach. In the simu-lations of vertical axis tidal turbines, the blade-vortex interaction is highlighted as the main phenomenon dominating the physics of these devices. The horizontal axis tidal turbine is simulated under differ-ent flow and turbulence intensity conditions, in both flat and irregular channel bathymetries. his thesis seeks to assess and enhance the per-formance, resilience and survivability of marine hydrokinetic devicesin their future deployment at sea