Hydrokinetic turbine array characteristics for river applications and spatially restricted flows

Highlights

Hydrokinetic turbine operation in multiple array configurations.

Steady state simulations using multiple reference frames to capture flow field.

Slight power reduction is predicted for lateral turbines as they get closer.

Downstream turbines produces significantly less power compared to upstream units.

Increased accuracy compared to lower fidelity, linear momentum actuator disk models.

Agreement between experimental results and numerical predictions.

Abstract

Multiple hydrokinetic turbines in three array configurations were characterized computationally by employing Reynolds Averaged Navier-Stokes equations. The simulations were conducted for pre-existing turbines operating at their optimum power coefficient of 0.43 which was obtained by design and optimization process. Mechanical power for two adjacent units was predicted for various lateral separation distances. An additional two-by-two turbine array was studied, mimicking a hydro-farm. Numerical simulations were performed using actual physical turbines in the field rather than using low fidelity models such as actuator disk theory. Steady state simulations were conducted using both Coupled and SIMPLE pressure-velocity solvers. Steady three dimensional flow structures were calculated using the kω Shear Stress Transport (SST) turbulence model. At a lateral separation distance of 0.5Dt, the turbines produced an average 86% of the peak power a single turbine producing. Interaction effects at lateral separation distances greater than 2.5Dt were negligible. The wake interaction behind the upstream turbines causes a significant performance reduction for downstream turbines within 6Dt longitudinal spacing. Downstream turbines employed for the present study performed around 20% or less of a single unit turbine performance for the same operating conditions. Downstream turbines yielded comparable reductions in power to that of experimental results.

Keywords

  • Micro-hydrokinetic turbines;
  • River applications;
  • Turbine performance;
  • Computational fluid dynamics;
  • Turbine array;
  • Hydro-farms

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