Abstract

A 2D coupled numerical model based on TELEMAC is established to simulate the hydrodynamics and sediment transport around tidal stream turbines in Zhoushan water, China. The effects of an array with 18 turbines on hydrodynamics and sediment transport are studied. The results show that the deployment of turbines results in an increase of velocity at the channel between Hulu Island and deploying area, which further leads to the increase of Suspended-sediment concentration (SSC). It is also demonstrated that bed erosion behind the array is significantly reduced, and even turns to deposition within the range of 20D on the north side of the turbine array.

Introduction

As a green, renewable and predictable marine energy, the rational development and utilization of tidal stream energy has been an important means to alleviate the energy crisis and reduce environment pollution. The coastal areas of China are abundant in tidal energy resource, estimated at 13.95GW, half of which is distributed in the water of Zhejiang province (Wang et al., 2011). The first tidal stream energy demonstration project is located in Zhoushan water, Zhejiang. The maximum tidal stream velocity there is above 1.7m/s and the water depth about 20m-60m (Wang et al., 2011). Although tidal stream generation has attracted much interests, the scientific basis on the effect of tidal stream turbines on the environment is still lacking (Frid et al., 2012). The environmental monitoring is an important way to study the influence of tidal stream turbines on hydrodynamics and sediment transport, but it needs a couple of years to get the feedback. Therefore, numerical modeling becomes an effective alternative for this purpose.

To date, many research works have been done on the impacts of tidal stream turbines on the surrounding hydrodynamics. Neill et al. (2009) investigated the influence of a tidal turbine farm in the Severn estuary (UK) by using a 1D numerical model. It is proposed that the energy extraction is analogous to increasing the bottom friction in the region of extraction, and then altering the hydrodynamic of the surrounding area.

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