Analysis of DMD for the Unsteady Transition Flow of the Wind Turbine Airfoil

The flow around the airfoil has a significant impact on the performance of the wind turbine. In this paper, large eddy simulation is used to obtain the unsteady transition flow of a wind turbine airfoil. Through the DMD analysis of the unsteady pressure flow field, the generation and the development of laminar separation bubble are found to be the main unsteady flow characteristics with a dominant frequency. The frequency of the highest amplification rate T-S wave is close to the frequency of the DMD mode. Therefore, the T-S wave at the downstream of the point of separation lead to the characteristic of K-H instability which dominants the periodic separation bubble. The DMD modes with middle and low frequencies are found to represent the turbulent structures caused by T-S waves. With the increase of the angle of attack, the separation bubble of the suction surface becomes shorter and moves to the leading edge while the separation bubble of the pressure surface changes little. © 2021, Science Press. All right reserved.