Multiscale Analysis of Flows Past Marine Hydrokinetic Devices Using Numerical Simulations

In this work, we seek to understand the effects that a farm of Marine Hydrokinetic (MHK) devices would have on the flow in the Chacao channel, Chile. We adopted a multi-scale approach to study the flow at the turbine scales and propose a parameterization for representing a group of turbines in the mesoscale. In Chapter II , we used the hybrid turbulence model DES coupled with the actuator disk approach to simulate staggered turbine configurations with different separations between devices and channel depths on an idealized domain. Using the time-averaged results, we obtained an expression for a new thrust coefficient representative of an entire farm of turbines, CtFarm, which only depends on the lateral and longitudinal separation of the devices and the number of rows of turbines. In Chapter III, we incorporated CtFarm into the ocean circulation model FVCOM, representing a specific finite farm of turbines in the Chacao channel. Firstly, we simulated a base case without devices to choose three suitable locations for installing a farm of turbines according to a commercial device's specifications. Then, we characterized the local bathymetry of the chosen locations to design an appropriate computational grid that considers the dominant bedforms. After simulating turbines, we observe variations in the velocity, turbulent kinetic energy (TKE), and shear bottom since these factors could affect the local ecosystem. The results showed that in flatter bathymetries, the magnitude of the percentage change in TKE and bottom shear is higher than in complex bathymetries since the presence of turbines represents a more significant alteration of the initial conditions. On the other hand, the absolute changes show that the initial conditions in velocity and TKE dominate the momentum extraction despite the bedforms because they have more power available. In this research, we were able to take the thrust force of a specific farm of turbines using high-resolution simulations and bring it to a larger scale model with realistic tides and bathymetries, which provides more insights to predict and mitigate the possible negative impacts of an MHK farm installation.