Abstract
Abstract. The aim of the present study is the validation of the implementation of an actuator disc (ACD) model in the computational fluid dynamics (CFD) code PHOENICS. The flow behaviour for three wind turbine cases is investigated numerically and compared to wind tunnel measurements: (A) the flow around a single model wind turbine, (B) the wake interaction between two in-line model wind turbines for a uniform inflow of low turbulence intensity and (C) the wake interaction between two in-line model wind turbines at different separation distances in a uniform or sheared inflow of high turbulence intensity. This is carried out using Reynolds-averaged Navier–Stokes (RANS) simulations and an ACD technique in the CFD code PHOENICS. The computations are conducted for the design condition of the rotors using four different turbulence closure models and five different thrust distributions. The computed axial velocity field as well as the turbulence kinetic energy are compared with hot-wire anemometry (HWA) measurements. For the cases with two in-line wind turbines, the thrust coefficient is also computed and compared with measurements. The results show that for different inflow conditions and wind turbine spacings the proposed method is able to predict the overall behaviour of the flow with low computational effort. When using the k-ε and Kato–Launder k-ε turbulence models the results are generally in closer agreement with the measurements.
Highlights
The study of wake properties is important for assessing the optimal layout of modern wind farms
The main conclusions of this study are summarized as follows: (i) the present results, considering the simplicity and low computational needs of the method, generally show satisfactory agreement between the simulations and the measurements used for both the set-up with one wind turbine and the set-up with two in-line wind turbines. (ii) The effect of using different thrust distributions on the profiles is generally present in the near wake and fairly absent in the far wake
The impact on the near wake is more pronounced for the set-up with a single wind turbine than in the set-up with two wind turbines. (iii) The uniform and undistributed thrust distributions generally outperformed the other distributions in terms of the estimated wake
Summary
The study of wake properties is important for assessing the optimal layout of modern wind farms. Wind turbine wake development may be studied using field experiments, smallscale wind tunnel measurements or numerical simulations with computational fluid dynamics (CFD). There are several advantages of CFD over field experiments and small-scale wind tunnel measurements, e.g. no violation of similarity requirements, control over inflow conditions and information about the relevant parameters, e.g. wind velocity, over the entire flow. Previous work on validating CFD wake models using a wind turbine tested in wind tunnels has been presented by Simms et al (2001) and by Schepers et al (2012). These studies demonstrated that there was a significant deviation between the various prediction tools and the wind tunnel measurements. Similar results for a small-scale model wind turbine are reported by Krogstad and Eriksen (2013) and by Pierella et al (2014), indicating the importance of validating existing wind turbine modelling tools and methodologies
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