Unsteady Reynolds-averaged Navier–Stokes investigation of free surface wave impact on tidal turbine wake

Abstract

Tidal current is a promising renewable energy source. Previous studies have investigated the influence of surface waves on tidal turbines in many aspects. However, the turbine wake development in a surface wave environment, which is crucial for power extraction in a turbine array, remains elusive. In this study, we focus on the wake evolution behind a single turbine and its interaction with surface waves. A numerical solver is developed to study the effects of surface waves on an industrial-size turbine. A case without surface wave and two cases with waves and different rotor depths are investigated. We obtain three-dimensional flow field descriptions near the free surface, around the rotor, and in the near- and far-wake. In a comparative analysis, the time-averaged and instantaneous flow fields are examined for various flow characteristics, including momentum restoration, power output, free surface elevation and vorticity dynamics. A model reduction technique is employed to identify the coherent flow structures and investigate the spatial and temporal characteristics of the wave–wake interactions. The results indicate the effect of surface waves in augmenting wake restoration and reveal the interactions between the surface waves and the wake structure, through a series of dynamic processes and the Kelvin–Helmholtz instability.

Single and multi-row turbine performance in bounded shear flow

“…The internal sub-problem is characterised by a range of turbine-scale features; these include local flow boundaries from neighbouring devices, the sea surface or seabed (for tidal). These boundaries can constrain the flow (Garrett & Cummins 2007) or even produce additional fluid dynamical phenomena like surface gravity waves (for tidal) which can have a direct impact on the turbine-scale flow and wake development (Li et al 2021). Note that, although gravity waves can impact wind farms as well (Ollier, Watson & Montavon 2018) they are considered as part of the external sub-problem for wind (unless they are strong enough to have a direct impact on the local flow pattern around each turbine).…”

Detent Force Reduction in Linear Interior Permanent Magnet Generator for Direct-Drive Wave Power Conversion

“…Considering the fact that 70% of the earth's surface is covered by oceans, wave energy has attracted increasing attention from scholars due to its higher energy density and global availability. Compared to the other sources of renewable energy, wave power is supposed to be the ideal and most promising energy resource [3][4][5]. The total wave energy resource around the world is estimated to be 10 TW, which is comparable to the world's power consumption.…”