Parametric Modal Decomposition of Dynamic Stall

Abstract

The chordwise, unsteady pressure difference field for harmonically oscillating airfoils operating in the attached flow, light dynamic stall, and deep dynamic stall regimes has been modally decomposed to identify well-defined modal structures that persist across a vast parameter space of pitching parameters (i.e., reduced frequency, mean angle of attack, and oscillation amplitude). The pressure difference fields were acquired at a chord Reynolds number and Mach number of and , respectively, demonstrating results applicable to rotorcraft flight conditions. Notably, only four mode shapes were required to reconstruct the aerodynamic loads anywhere within the parameter space. Likewise, the same mode shapes showed a remarkable ability to reconstruct the aerodynamic loads of other (non-native) airfoil geometries with a similar precision. The parametric modal decomposition outlined provides a foundation to elucidate the physics of the dynamic stall phenomenon as well as reduced-order modeling techniques for the aerodynamic loading.