Mechanisms of rotational curvature correction in separated flows through modal decomposition

This study investigates the influence of rotational curvature correction on the SST-DDES in predicting high angle of attack separated flows over the NACA4412 airfoil, as well as the underlying mechanisms. The DDES method used (Gritskevich and Menter) employs globally unified model equations with modified dissipation only, thereby ensuring the RANS-based rotational curvature correction remains effective throughout the flow field, including in massive separation. The findings reveal that the rotational curvature correction enables improved capture of vortex structures and mitigates unphysical model behavior. The proper orthogonal decomposition analysis demonstrates that the correction enables a more accurate depiction of the energy distribution of wake vortices, with particular emphasis on the precise identification of secondary energy structures. Furthermore, spectral proper orthogonal decomposition highlights that correction significantly improves the spatial distribution of eddy viscosity, particularly in terms of its ability to reasonably capture high-frequency fluid squeeze and separation bubble breakdown patterns near the trailing edge. Additionally, the correction modifies critical terms in the turbulent kinetic energy(TKE) transport equation, optimising the predictions of the eddy viscosity and the TKE. This study employs multiple analytical perspectives to extract critical information embedded within different modes.