The CFD Investigation of Two Non-Aligned Turbines Using Actuator Disk Model and Overset Grids

In this study flow over two axially non-aligned wind turbines is investigated via 3-D CFD analysis by solving Navier-Stokes equations. This setting is the test case geometry for the NTNU's "Blind-Test" Workshop 3 (BT3) and it aims to predict the performance of the wind turbines and their wake development under asymmetrical flow conditions. The performance of the turbine in the wake of the other turbine is numerically studied for different tip speed ratios. The measurements of velocity profile which is severely disturbed by both turbines are also carried out at the several locations of the wind tunnel. The computational results for NTNU wind turbine test case were obtained by 3-D CFD simulations with two different approaches. The first approach is to employ the actuator disk model, which is used in order to approximate the pressure jump across the rotor disk to simulate the impact of the wind turbines. At the second approach, the actual geometry of the turbine rotor was used, and the rotor blades were rotated using an overset grid methodology over the background grids. The thrust coefficients and the velocity profiles are calculated with two different approaches and the results are compared to experimental data presented in BT3.