采用计算流体动力学(CFD)方法,在恒定大攻角工况下,对风力机翼型的非定常流场进行数值模拟,并采用动力模态分解(DMD)方法对其模态进行辨识,以得到非定常流场的频率和相应的主要模态.结果表明:DMD方法可用于分析非定常流场的变化过程;DMD的各阶模态描述了非定常流场的主要流动特征,流场中非定常流动主要集中在近尾迹区域;采用包含主要流动信息的前4阶模态重构的流场能够反映不同时刻的时域流场;第2阶DMD模态重构的流场可以直观地描述尾迹区域内2个方向相反的涡依次脱落并向下游传播的非定常流动特征.
The unsteady flow field is calculated by the computational fluid dynamics (CFD) method, around a wind turbine airfoil at high angle of attack, and its modes are identified by using the dynamic mode decomposition (DMD) method. The dominant modes and corresponding frequencies are obtained. The results show that the DMD method can be used to analyze the changing process of the unsteady flow field; the DMD modes capture the main flow structure of the unsteady flow field, and the main unsteady flow is around the near wake region; the flow field, reconstructed by 4 DMD modes, could describe the original unsteady flow field; the flow field reconstructed by the second DMD mode describe that two vortexes, whose rotating directions are opposite, shed and spread into downstream in turn.
[1]RIVAL D, TROPEA C. Characteristics of pitching and plunging airfoils under dynamicstall conditions[J]. Journal of Aircraft, 2010, 47(1): 8086.
[2]GARDNER A D, RICHTER K, MAI H, et al. Experimental investigation of dynamic stall performance for the EDIM109 and EDIM112 airfoils[J]. Journal of the American Helicopter Society, 2013, 58(1): 113.
[3]ZANON A, GIANNATTASIO P, SIMOF C J. A vortex panel model for the simulation of the wake flow past a vertical axis wind turbine in dynamic stall[J]. Wind Energy, 2013, 16(5): 661680.
[4]YU G H, ZHU X C, DU Z H. Numerical simulation of a wind turbine airfoil: Dynamic stall and comparison with experiments[J]. Proceedings of the Institution of Mechanical Engineers. Part A: Journal of Power and Energy, 2010, 224(5): 657677.
[5]TISSOT G, CORDIER L, BENARD N, et al. Model reduction using dynamic mode decomposition[J]. Comptes Rendus Mécanique, 2014, 342(6/7): 410416.
[6]BAROCIO E, PAL B C, THORNHILL N F, et al. A dynamic mode decomposition framework for global power system oscillation analysis[J]. IEEE Transactions on Power Systems, 2015, 30(6): 29022912.
[7]SCHMID P J. Dynamic mode decomposition of numerical and experimental data[J]. Journal of Fluid Mechanics, 2010, 656: 528.
[8]MULD T W, EFRAIMSSON G, HENNINGSON D S. Flow structures around a highspeed train extracted using proper orthogonal decomposition and dynamic mode decomposition[J]. Computers and Fluids, 2012, 57: 8797.
[9]LIU Y, ZHANG Q. Dynamic mode decomposition of separated flow over a finite blunt plate: timeresolved particle image velocimetry measurements[J]. Experiments in Fluids, 2015, 56(7): 117.
[10]DUNNE R, MCKEON B J. Dynamic stall on a pitching and surging airfoil[J]. Experiments in Fluids, 2015, 56(8): 115.
[11]SCHMID P J. Application of the dynamic mode decomposition to experimental data[J]. Experiments in Fluids, 2011, 50(4): 11231130.