Computational investigations of vortex dynamics and dynamic stall of pitching airfoils at high Reynolds number

Abstract

This study employs high-fidelity Detached Eddy Simulations (DES) and modal decompositions to elucidate dynamic stall mechanisms on a pitching NACA 0018 airfoil at 𝑅𝑒 = 160000. Proper Orthogonal Decomposition (POD) isolates leading‐edge separation bubbles, shear‐layer instabilities, and wake vortices by energy content, while Dynamic Mode Decomposition (DMD) and multiresolution DMD (mrDMD) reveal mode‐specific growth/decay rates and frequencies across reduced frequencies (𝑘 = 0.1,0.2,0.3) and amplitudes (𝛼=15−30°). DMD captures key events—LSB bursting, LEV formation, and DSV convection—with global modes sufficient for most cases, whereas mrDMD improves reconstruction only under deep stall (𝑘 = 0.1,𝛼=30°) These findings provide a low-order framework for predicting unsteady loads and guiding stall mitigation strategies.