Assessment of turbulence correction for actuator-line model of a horizontal-axis tidal stream turbine in near-wake region

Abstract

Near-wake characteristics of a turbine play an important role in turbine-wake interactions and performance assessment in turbine arrays. In this study, the near-wake flow behind a laboratory-scale tidal stream turbine is simulated and compared with experimental data. An actuator-line model is used to represent the rotating blades. Further, two physics-based turbulence corrections are proposed for unsteady Reynolds-averaged Navier-Stokes (URANS) modeling of the tidal stream turbine. These corrections seek to model additional turbulent production near the blade boundary layer and in the tip shear region. The data analysis for the fluctuating velocity spectrum in the experiment highlights that the turbulence kinetic energy (TKE) can be decomposed into three parts: the background turbulence from the onset flow, rotor-scale turbulence, and blade-induced turbulence. The blade-induced turbulence dominates near the rotor plane and decreases sharply beyond one diameter downstream. Near-wake profiles of velocity and TKE are compared with experimental data. The results show that turbulence corrections in the URANS model enhance the production of turbulence induced by the blade rotation. It can improve turbulence prediction in the near-wake region with a minor impact on the loads and wake velocity.