Steady State and Transient Computational Study of Multiple Hydrokinetic Turbines

Computational fluid dynamics (CFD) simulations have been conducted for different configurations of pre-designed multiple hydrokinetic turbines. The turbines are modeled physically within the fluid domain instead of low fidelity actuator lines or actuator disk modeling approaches. The turbulence model, k-o Shear Stress Transport (SST) was employed to resolve turbulent flow field. The primary focus of this study is to investigate transient behavior of multiple turbines and providing solutions to enhance downstream turbine performance in close proximity to the upstream turbine wake. The wake interaction behind the upstream turbine reduces downstream turbine performance with inline configurations being the most severe cases. One of the many suggested solutions is staggering downstream units beyond the wake region. Other solutions for an inline array: increasing the longitudinal distance between units and modifying downstream turbine rotation speed to move turbine operation point to the best efficiency point.;The CFD simulations revealed that the upstream turbine power generation is nearly the same with the single unit power generation for each multiple turbine arrangement. The downstream turbine relative power obtained was 0.18 for the unit placed inline and 0.98 when it was placed outside the wake region. For inline configurations, increasing the stream-wise spacing between the units from 6Dt to 10Dt improved relative power from 0.16 to 0.60, while reducing the rotation speed from 150 rpm to 100 rpm resulted relative power increment from 0.24 to 0.55.