RESEARCH on CHAOTIC FEATURES of A FLOW FIELD over A PLUNGING AIRFOIL BASED on DYNAMIC MODE DECOMPOSITION

Periodic motion of a plunging airfoil causes continuous changes in the surrounding flow field. The time-dependent thrust coefficient depends entirely on unsteady characteristics of the flow field. On the contrary, the time-dependent thrust coefficient may also reflect the unsteady characteristics of the corresponding flow field. With the fast Fourier transform (FFT) and dynamic mode decomposition (DMD), unsteady aerodynamic forces can be correlated with the flow field characteristics in the frequency domain. In the present paper, DMD is performed to analyze the unsteady characteristics of the flow field around a plunging NACA0012 airfoil at the Reynolds number of 20 000.