Numerical simulation of the effect of axial distance between two rotors in counter-rotating wind turbines

The counter-rotating wind turbines (CRWT) is a wind turbine model developed from a single rotating wind turbine (SRWT) model with a horizontal axis. CRWTs have two rotors rotating in opposite directions on the same axis. The purpose of this research is to find the optimal power that can be produced by CRWTs, as related to the change of the axial distance between the front and rear rotors. The flow around CRWTs is simulated using computational fluid dynamic (CFD) with ANSYS Fluent. The simulation consists of two steps: obtaining the optimum rotation and rotor torque, respectively. These two values are used to calculate the mechanical power of the rotors. In this simulation, the wind velocity is 3 m/s and the variations of axial distance are 0.2d; 0.3d; 0.44d; 0.61d; 0.7d; 0.8d; 1d; 1.5d; 2d (with d standing for front rotor diameter). The result of the simulation shows that axial distance between 0.2d– 0.7d has the most optimal mechanical power.