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A prerequisite in undertaking large-scale developments and utilisation of tidal current energy is to comprehend the hydrodynamic characteristics of the wake field of tidal current turbines. The wake of an upstream turbine can strongly affect the power output of downstream turbines and their arrangement. The structure of turbine wakes was investigated. One experiment was conducted on a two-bladed horizontal turbine in a laboratory flume. Actuator disc momentum theory, combined with Reynolds-averaged Navier–Stokes equations, was used to parameterise the tidal turbine. The numerical model was validated using experimental data. The degree of wake mixing improved when the axial distance was eight times the turbine diameter (8D) or larger. The influence of the arrangement and spacing of turbines was investigated at two tidal farms, one with three aligned turbines and one with seven staggered turbines. The incoming flow velocity of the downstream turbine was reduced by 31% when turbines were linearly aligned. The extent of influence of the third column was larger than that of the second column, indicating an expanding wake. Different lateral spaces of staggered turbines were analysed. Different distances between rows strongly influenced both the incoming velocity of downstream turbines and the expansion of the whole wake. The incoming flow of the third column reduced by 31, 17 and 16% with increasing lateral space. The flow velocity increased as water passed over the turbine tip. For staggered turbines, a centreline spacing of up to 1.5D for adjacent rows is recommended.

The effect of stanchion and reverse flow on turbine power performance is studied based on Computational Fluid Dynamics (CFD). The turbine in this paper is developed by National Ocean Technology Center (NOTC), the experiment study has been carried out in year 2014. The simulation model is validated based on experimental results. The CFD model can simulate the marine current conditions up to an acceptable accuracy and is cost-effective compared with experimental work. The mesh dependent including prism layer cell mesh has been studied. There are two methods in simulating the turbine power performance which aer steady-state and transient model. We compared the results of these two methods, the difference of Cp was within 2% based on the same mesh size. The results of two methods showed little difference. We chose the steady-state method in the rest of the calculation to maintain the better economically computational model. The effect of different size of the rotating zone is calculated in the model. The results showed that the biggest gap is 1.06%, the size of rotation zone has little impact to the turbine performance. We simulated cylindrical stanchions with different distance against to turbine. Simulation model is established based on the validated model. The power coefficient curves were given based on simulation results. The results showed that the largest drop reached 25.3% between different distances. The effect of bi-directional flow to turbine power performance is studied through simulation model. The power decrease could reach 21.7% when the turbine is backward to the tidal flow is calculated and graphed. The numerical model established in this paper can simulate the performance of turbine well, The result can provide technical support for engineering application of tidal turbine.