703 Numerical simulation of flow around Vertical Axis Wind Turbine with Large Eddy Simulation(2)

The final goal of this investigation is to develop high performance vertical axis wind turbines for clean energy supply systems. For this purpose, we attempted to simulate flow around a vertical axis wind turbine with LES. Since the angles of attack of VAWT are widely changed during rotor rotation, the large scale separation and interaction between the turbulent wakes are occurred. Therefore, unsteady and high accuracy simulation is necessary to simulate flow around the VAWT. Large Eddy Simulation with sliding mesh technique was utilized to solve the complicated flow around the VAWT. The numerical results show the large separation occurred and unsteady aerodynamic forces were observed in the wake of VAWT. The ratio of negative torque generated period to rotor rotation time was small at tip-speed ratio (TSR) of 3. Therefore, the maximum power coefficient can be obtained at TSR of 3. In the case of high TSR ratio, the predicted results were reasonably agreement with that of the momentum theory. However, the discrepancy of torque coefficient between the results of LES and momentum theory were large at low tip-speed ratio. The discrepancy seems to occur with the effect of dynamic stall. It revealed that the LES is suitable method to estimate the performance of VAWT..