Experimental study on transition of dynamic airfoil in pitching oscillation

Abstract The transition characteristics of dynamic airfoil have significant effects on the aerodynamic performance wind turbines, helicopter rotor blades, jet engine compressor etc. time domain and time-frequency a NACA0012 during its pitching oscillation were experimentally studied using wall pressure measurement technology with high accuracy in this paper. variable slip window was used to detect position, proper orthogonal decomposition (POD) method wavelet analysis combined perform analysis. In gradual forward movement transition, low-frequency instability is gradually enhanced by main flow inverse gradient, significantly submerges high-frequency fluctuated feature. higher order moments deviate from Gaussian characteristics, which caused burst. POD able distinguish reduced frequency had transition. With increase frequency, hysteresis effect became more significant, component concentrated energy stronger.