Aerodynamic interference and flow field mechanisms of three-dimensional tandem square cylinders based on proper orthogonal decomposition and high-order dynamic mode decomposition modeling

This work proposes a novel reduced-order model that integrates proper orthogonal decomposition (POD) and high-order dynamic mode decomposition (HODMD) to explore the dominant aerodynamic modes and interference mechanisms of three-dimensional finite-length tandem square cylinders. By leveraging POD to extract spatially dominant mode characteristics and integrating HODMD's amplitude-dominant modes to identify those significantly contributing to interference effects, results demonstrate that the POD-HODMD model can be effectively applied to the study of interference effects in three-dimensional finite-length tandem square cylinders, providing a robust method for reduced-order analysis of complex flow field data. The interference effects significantly influence the aerodynamic characteristics of the structures within the vortex shedding frequency bandwidth, and various structural spacings modify the positions of shear layer separation and reattachment, as well as their combined effects with the inter-structural flow field on the pressure distribution patterns on each surface of the structures. The interference effects on the flow field patterns vary across different frequency ranges. Low-frequency modes reshape gap vortex distributions and velocity orientations at structural ends, while high-frequency modes modify gap vortex distributions at the mid-span plane and wake continuity of the disturbed structure. The vortex shedding mode causes separation and wake vortices to become fuller and larger in scale. This technology not only provides a systematic method for analyzing aerodynamic and flow field characteristics for tandem structures but also deepens insight into the intricate dance of fluid–structure interactions within such configurations.