基于剪切应力输运湍流模型的SST-DDES混合方法对NACA0012翼型大迎角分离流动进行非定常数值模拟,采用动力学模态分解(Dynamic Mode Decomposition,DMD)数学工具对失速初始状态、浅失速状态以及深失速状态的流场进行稳定性分析.结果表明:DMD方法准确地提取了翼型大迎角流动中的主频和高阶倍频及对应的流场模态结构;与FFT分析结果相比,频率最大差异小于0.16％;且发现两者提取的频率在流动中的主导作用顺序也一致.通过特征值对相应的模态进行稳定性分析,所有模态的放大率均非常小,所有模态处于弱发散、弱收敛或稳定极限环状态.DMD提取的一阶模态主要表现为分离涡演化过程中最主要的静止分离涡结构,前三阶低频对应的模态涡结构与流动中以此频率进行演化的涡结构比较一致,更高阶的倍频主要表现为尾涡和尾迹区的涡结构.且发现不同模态系数之间存在相位差,说明分离涡流动中不同频率对应的涡结构运动不同步.%The NACA0012 airfoil at high angle of attack is simulated by the hybrid SST-DDES method based on the shear stress transport (SST)turbulence mode.The stability of the flow field is analyzed by using the mathematical tool dynamic mode decomposition (DMD)in the initial stalled state,shallow stalled state,and deeply stalled state.The results show that the DMD method can be used to accurately extract the dominant frequency,high order frequency doubling,and the corresponding flow field mode structures in the airfoil flow at high angle of attack.Compared with the fast Fourier transform (FFT)analysis results,the maximal difference of the frequency is less than 0.16％,and the leading role order of both extracted frequencies in the flow is the same.By analyzing the stability of the corresponding mode through eigenvalue,the growth rates of all modes are very small.All modes are weak divergent,weak convergent or in the stable limit cycle state.The first order mode reflects the main static separation vortex structure in the vortex evolution process.The mode vortex corresponding to the first three low frequencies is consistent with the vortex structure evolved in this frequency.The higher order frequencies mainly reflect the trailing vortex and the vortex structure in the wake region.It is found that there are phase differences between the different mode coefficients.This indicates that the movement of the vortex structures of different frequencies is asynchronous in the separated flow.
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