Numerical Simulation of Wind Turbine Wake Characteristics by Flux Reconstruction Method

In the paper, a CFD method that employs the flux reconstruction (FR) method and the actuator line (AL) method is proposed, to develop a novel numerical framework to improve the efficiency and accuracy of turbulent wake predictions of horizontal axis wind turbines (HAWT). The PyFR solver, which is an open-source program that uses the FR method is applied. The actuator line method is for the first time implemented in the FR solver to simulate HAWTs. To increase the fidelity of the wake prediction, the nacelle and tower of the HAWT are also modeled, and the proposed numerical simulation method is named as AL-PyFR(N&T) model. The NTNU “Blind Test 1” wind turbine is used to validate the proposed model. First, the mesh and time step dependence of the AL-PyFR(N&T) model are verified. Second, the accuracy of the proposed model is verified by comparing the velocity deficits and turbulent kinetic energy results at different downstream locations with the measured values and the results from other CFD studies. The characteristics of the wake velocity deficits are analyzed by using the numerical simulation results. By comparison of the results with and without the effect of the nacelle and tower, it is found that the wake asymmetry is mainly due to the influence of the tower. Through this study, it is demonstrated that by using the proposed AL-PyFR(N&T) model, accurate HAWT wake predictions can be achieved with fewer mesh numbers than conventional CFD solvers, which is suitable for high-fidelity numerical simulations of offshore wind farms.