Abstract
To study the performance and environmental impacts of marine hydrokinetic (MHK) turbine arrays, we carry out an investigation based on laboratory experiments and numerical models able to resolve the dynamics of turbulent wake interactions and their effects on the river bed. We investigate a scaled Sabella D10 mounted on a mobile bed for a single and two aligned turbines, measuring the flow velocity, the rotor angular velocity, and the scour on the sediment bed. Numerical simulations are performed using a detached-eddy simulation (DES) turbulence model coupled with the blade-element momentum (BEM) approach, which can capture the mean flow and resolve the dynamics of turbulent coherent structures in the wakes. The simulations show a good agreement on the velocity statistics obtained experimentally. Power and thrust coefficients for the downstream turbine show an average decrease and a larger variability due to the turbulent intensity produced by the upstream turbine, as compared to the single turbine case. Results of this investigation also provide a framework to assess the predictive capabilities, scope, and applicability of computational models parameterizing the turbines using BEM, for testing different turbine designs and siting strategies within the MHK array.
Highlights
Tidal currents have a significant potential to contribute to the global energy supply in the near future
We combine the analysis of experiments and simulations with two main objectives: (1) characterizing the flow fields in the wakes downstream of Sabella D10 turbines, for a single device and two devices installed in tandem, analyzing the hydrodynamic features of the wake generated by these horizontal-axis tidal turbines (HATTs), which are characterized by a large hub and nacelle and six symmetrical blades; and (2) evaluating the advantages, accuracy, and scope of the detached-eddy simulation (DES)-blade-element momentum (BEM) model for these turbines, identifying under which conditions we can consider this approach to simulate turbine arrays accurately
The results obtained from the simulations suggested that some characteristics of the turbine interaction could be represented by DES-BEM model, while the bed elevation asymmetry in the wake, coincident with the skewed location of the maximum velocity deficit shown in Figure 4, suggested including the support structure in the simulation to better capture the effects of the turbine on the bathymetry
Summary
Tidal currents have a significant potential to contribute to the global energy supply in the near future. It is important to define the scientific question that motivates the development of the model to determine the level of detail required for the specific modeling approach In this investigation, we carry out an experimental study coupled with numerical simulations of a Sabella D10 MHK turbine. (1) characterizing the flow fields in the wakes downstream of Sabella D10 turbines, for a single device and two devices installed in tandem, analyzing the hydrodynamic features of the wake generated by these HATTs, which are characterized by a large hub and nacelle and six symmetrical blades; and (2) evaluating the advantages, accuracy, and scope of the DES-BEM model for these turbines, identifying under which conditions we can consider this approach to simulate turbine arrays accurately.
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