The impact of evaluation method on the performance of the horizontal axis marine current turbine

There are several methods currently available to characterise and analyse the hydrodynamics of a marine current turbine. Selection of an appropriate and accurate method is important at all stages of turbine research, development and implementation. Blade Element Momentum (BEM) theory is a useful tool to attain a quick power prediction of a marine current turbine [1]. Numerical simulation is highly useful for the analysis of different hydrodynamic problems, including turbine performance; however, they need to be validated by experimental data. Experiments can provide detailed results on scale models and allows the characterisation of turbine performance by controlling different parameters during tests. However, some intrinsic characteristics of a facility may limit the applicability of model experimental results.

In this work, an experimentally validated BEM model developed by Walker, et al. [2] was utilized to assess the performance of a horizontal axis marine current turbine in steady condition and then developed to account for shear flow profile. The Reynolds number effect was also studied using QBlade software. The numerical simulation was performed using ANSYS CFX and the experiments were implemented in the Towing Tank and Circulating Water Channel (CWC) of the Australian Maritime College (AMC), providing steady and unsteady condition of the flow respectively. To have consistency in the comparison study, all the evaluation methods were applied on two scale model turbines with 800 mm and 500 mm diameter, shown in Figure 1.

The different turbine performance assessment methods are compared in Figure 2 for the 800 mm diameter turbine model. In this figure, the CFD simulations and the towing tank experiments are at an inflow velocity of 2 m/s, whilst the CWC experiments are at 1.3 m/s. The experimental results on a same turbine model at the United States Naval Academy are also shown for comparison. The BEM result is based on lift and drag coefficients from the 2D wind tunnel tests and the flow velocity profile of the CWC.