Comparative Evaluation of Vorticity Transport Modeled Distortions and High-Fidelity ANSYS Solutions Using Modal Assurance Criterion

Abstract

Swirl of any magnitude present at the AIP has been shown to have the potential to drastically impact the performance of fan-based propulsion systems. This work presents the evaluation of a vorticity transport based reduced order model (ROM) in comparison to similar data created through Ansys CFX simulation for three canonical swirl flow profiles: Bulk Swirl, Twin Swirl, and Quad Swirl. Modal decomposition through singular value decomposition (SVD) is performed on the resulting in-plane velocity profiles for both the ROM and high-fidelity RANS simulations. The accuracy of the ROM is assessed through both conventional error analyses and a novel-energy-weighted modal assurance criterion (MAC) methodology. The MAC based error methodology is proposed to distinguish ROM performance across dominant and minimally contribution mode content. The results and conclusions for this research effort show through conventional L1 error analysis a growth of absolute error with respect to propagation distance. However, the effectiveness of the ROM across dominant low wavenumber flow features with near perfect MAC agreement (MAC = 1.0) is simultaneously observed. Further MAC analysis of the high wavenumber modes shows a reduction in modal matching as wave number increases suggesting the ROM's sensitivity to viscous effects.