Experimental Analysis and Evaluation of the Numerical Prediction of Wake Characteristics of Tidal Stream Turbine

Yuquan Zhang,Jisheng Zhang,Chunxia Yang,Wei Zang,E Fernandez-Rodriguez,Yuan Zheng

doi:10.3390/en10122057

Abstract

It is important to understand tidal stream turbine performance and flow field, if tidal energy is to advance. The operating condition of a tidal stream turbine with a supporting structure has a significant impact on its performance and wake recovery. The aim of this work is to provide an understanding of turbine submerged depth that governs the downstream wake structure and its recovery to the free-stream velocity profile. An experimentally validated numerical model, based on a computational fluid dynamics (CFD) tool, was present to obtain longitudinal, transverse and vertical velocity profiles. Wake characteristics measurements have been carried out in an open channel at Hohai University. The results indicate that varying the turbine proximity to the water surface introduces differential mass flow rate around the rotor that could make the wake persist differently downstream. CFD shows the same predicted wake recovery tendency with the experiments, and an agreement from CFD and experiments is good in the far-wake region. The results presented demonstrate that CFD is a good tool to simulate the performance of tidal turbines particularly in the far-wake region and that the turbine proximity to the water surface has an effect on the wake recovery.

Highlights

Ever-increasing pollution emissions from energy supplies derived from fossil fuels are considered as one of the most critical threats for society, and the release of greenhouse gases is responsible for the change of climate [1]
Among various forms of ocean energy, tidal energy is much more stable and predictable compared with wave energy and others
One of the categories to extract tidal energy is the tidal stream generator, in which water flow is interrupted by the tidal stream turbine (TST) to drive a generator, which minimises the impact on the marine environment

Summary

Introduction

Ever-increasing pollution emissions from energy supplies derived from fossil fuels are considered as one of the most critical threats for society, and the release of greenhouse gases is responsible for the change of climate [1]. It is paramount to exploit sustainable resources to satisfy our needs [3]. The ocean covers almost 71% of our earth and has a huge amount of energy resources of more than 2 × 103 TW [4]. Among various forms of ocean energy, tidal energy is much more stable and predictable compared with wave energy and others. One of the categories to extract tidal energy is the tidal stream generator, in which water flow is interrupted by the tidal stream turbine (TST) to drive a generator, which minimises the impact on the marine environment. The TST has no visual impact as it is usually fully submerged

Objectives

Methods

Results

Conclusion