OUTPUT-ONLY SYSTEM IDENTIFICATION OF LOW-FREQUENCY FLOW OSCILLATIONS OVER AN AIRFOIL NEAR STALL
We present output-only system identification of the self-sustained low-frequency flow oscillations over an LRN (1)-1007 airfoil at a chord-based Reynolds number of Re = 10 near stall conditions. We model the lift force fluctuations with a Van der Pol oscillator subjected to stochastic white noise, which represents the effect of intrinsic turbulence. The parameters of this low-order model are identified from the time series of the lift force acquired by a load cell. We extract the drift and diffusion coefficients of the resulting Fokker-Planck equation and optimize them with an adjoint-based algorithm. Based on these coefficients, the linear growth rate, non-linear saturation coefficient and noise intensity are identified, enabling reconstruction of the probability density functions of the oscillation amplitude. Moreover, by extrapolating the parameters found in the pre-bifurcation regime, we are able to predict the location of the Hopf point as well as the post-bifurcation behaviour. This framework can thus provide early warning indicators of low-frequency flow oscillations, facilitating the design of new control strategies.
|Document Type||Conference paper|
|Department||Department of Mechanics and Aerospace Engineering|
1.Division of Emerging Interdisciplinary Areas,Hong Kong University of Science and Technology,Clear Water Bay,Hong Kong
2.Department of Mechanics and Aerospace Engineering,Southern University of Science and Technology,Shenzhen,518055,China
3.Department of Mechanical and Aerospace Engineering,Hong Kong University of Science and Technology,Clear Water Bay,Hong Kong
Zhai，Xiangyu,Gupta，Vikrant,Redonnet，Stephane,et al. OUTPUT-ONLY SYSTEM IDENTIFICATION OF LOW-FREQUENCY FLOW OSCILLATIONS OVER AN AIRFOIL NEAR STALL[C],2023.
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