Transient analysis of micro-hydrokinetic turbines for river applications

Transient simulations are conducted to characterize a single turbine and multiple turbines in an inline and a staggered array using k-ω shear-stress transport (SST) turbulence model. Performance characteristics predicted by transient analysis at various operating conditions were compared to those predicted by steady-state analysis. Transient results indicated that a power coefficient of 0.43 would be generated at the best efficiency point which corresponds to 1.4% deviations between transient and steady-state solutions for a single unit. Flow separation is observed at the tip speed ratio lower than that at the design point. The relative power of the upstream turbine is obtained to be nearly unity in both inline and staggered arrays. The relative power of the downstream turbine in the staggered array is not influenced by the presence of the upstream turbine and it is the same as that of the upstream turbine. On the other hand, the relative power of the downstream turbine in an inline array is reduced to 0.18 at a downstream separation of 6Dt. The massive drop in the power generation by the downstream turbine resulted from the presence of strong wake flow induced by the upstream turbine.