Yemeng Xu

Fluid–structure interaction (FSI) in wind-sensitive structures arises from a closed exchange among separated flow, surface traction, structural motion, and wake reorganization. This review compares experiments, numerical methods, reduced-order models, and learned surrogates through the feedback and interface quantities they retain. Mono-directional analysis is distinguished from bi-directional FSI according to whether the computed structural motion is returned to the flow. That distinction determines which pressure phase, wake state, and aerodynamic work can be represented. The synthesis leads to two conclusions. First, agreement in force or response amplitude alone is insufficient near an instability boundary because an error in load–motion phase can reverse the inferred aerodynamic work. Second, neither fine flow field resolution nor a learning architecture guarantees power-consistent transfer across a moving interface; this property must be imposed or verified separately. Experimental methods are therefore assessed through synchronized load, motion, and flow observables, and numerical and learned models through interface consistency, response regime coverage, and uncertainty. These criteria guide model selection for bluff-body vibration, bridge and building response, flexible membranes, and related wind-sensitive systems.

Highly flexible bluff-body structures are susceptible to nonlinear wind-induced vibrations, which may cause serviceability loss. Fluid–structure interaction (FSI) is central to this process. However, most existing studies focus on the aerodynamics of rigid structures, and the evolution of structural flow fields and underlying mechanisms under FSI remains insufficiently clarified. To address this gap, this study examines a finite-length square cylinder with a large height-to-width aspect ratio (18:1). Using a moving-mesh large-eddy simulation framework, we systematically investigate the effects of uniform inflow at reduced velocities Vr = 10, 26, 30 on pressure distribution, mean pressure coefficients, time-averaged flow, time-averaged vorticity, and coherent vortical structures. The results indicate that FSI markedly alters both the surface pressure distribution and the surrounding flow features. On the leeward face, the negative-pressure zones near the top and bottom edges expand, and the suction intensity is weakened by structural vibrations. At the fixed end, the compression of the windward recirculation bubble is significantly reduced. The downstream recirculation region elongates and becomes less sensitive to wind speed, and the upwash within the wake weakens appreciably. Away from the base region, vibration shifts the flow's topological focus, leading to reduced negative pressure at mid-height on the leeward face and near top of the side face. Vibration also modifies the periodic spatial pattern of the wake. This study systematically elucidates the coupled effects of structural motion and inflow conditions, overcoming the limitations of previous studies that mainly focused on the aerodynamic response of rigid structures, and further deepening the understanding of the overall FSI response mechanism.

Fluid–structure interaction (FSI) is a fundamental problem in fluid mechanics, which is prevalent across diverse practical engineering applications and has a significant impact on the safety and reliability of structures. In this study, large eddy simulation is employed to perform numerical simulations of a three-dimensional finite-length isolated square cylinder under varying incoming flow velocities and prescribed crosswind vibration states in a turbulent inflow. This configuration, combining finite-length structure, structural vibration, and turbulent flow, is designed to closely mimic realistic wind-resistant conditions encountered in engineering practice. Based on the mean pressure coefficients and flow field phenomenology, the FSI mechanisms are systematically examined in two distinct regimes. Within the vortex-induced vibration (VIV) velocity range, structural vibration markedly modifies the behavior of the separated shear layers, leading to significant changes in the distributions of mean pressure coefficients, wake topology, vortex shedding, and three-dimensional vortex structures compared with the rigid square cylinder. At high wind velocity, however, the influence of structural vibration becomes weak and the FSI response is instead governed predominantly by the incoming flow, and the flow field exhibits characteristics that are different from those in the VIV regime. This study is expected to deepen understanding of how both structural motion and inflow conditions jointly control the global FSI response under this realistic configuration, and to provide a reference for subsequent related studies.

This study integrates Proper Orthogonal Decomposition (POD) and High-Order Dynamic Mode Decomposition (HODMD) reduced-order model (POD-HODMD), combining POD's energy-ranking capability with HODMD's frequency uniqueness, which establishes systematic correlations, energy, and frequency. Using POD-HODMD as a tool, the study analyzes the flow characteristics of a three-dimensional square prism through integrated wind tunnel tests and computational fluid dynamics simulations. The results reveal three dominant frequency bands: the vortex shedding band, the low-frequency band, and the high-frequency band. The vortex shedding band governs the crosswind force, driven by flow separation and reattachment at the structure's edges, forming a C-shaped pressure gradient and periodic vortex shedding in the wake. The low-frequency band dominates the along-wind force, manifested through a significant pressure difference between the windward and leeward sides, accounting for large-amplitude low-frequency vibrations. The high-frequency band induces instantaneous vortex generation and dissipation, leading to turbulent fluctuations. The reduced-order model effectively identifies dominant modes in both the pressure and velocity fields and facilitates quantitative characterization of the dynamic interactions between wind and structure. This research offers a robust tool for improving structural safety and wind load predictions in wind engineering.

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.

The current research primarily focuses on interference effects in rigid structures, with the omission of the feedback impact of structural vibration on the flow field preventing the disclosure of the intrinsic mechanisms behind interference effects. Therefore, this study analyzed the aerodynamic characteristics and flow field phenomena of the finite-length side-by-side square prisms under vibration through the large eddy simulation, unveiling the flow field morphology and disturbance mechanisms. The results show that the three-dimensional effect of the side-by-side square prisms effectively suppresses the deflection of the gap flow. Structural vibration increases the curvature of the shear layers on both sides of the interfering structure, weakens its end effect, and destroys the integrity of the axial vortex in the wake region. With the increase in the spacing between the side-by-side square prisms, the “narrow pipe effect” is weakened, the flow acceleration is relatively slowed down, and interference of the vortices in the wake region is weakened. In addition, some typical flow field phenomena are observed, such as gap flow instability, coupled vortex street, interaction of wakes, and different flow regimes. This study is of great significance for understanding mechanisms of the flow interference around the finite-length side-by-side square prisms under fluid–structure interaction.

This study conducts large eddy simulations (LES) to investigate the aerodynamic interference effects and flow field characteristics of the flow around square cylinders, taking into account the inclination of the disturbed structure. The configurations of the structures involve tandem and side-by-side arrangements with the inclination angles of the disturbed structure including +15°, 0°, and −15°. The identification of flow field characteristics involves the examination of multiple components, particularly time-averaged velocity streamlines, axial flow patterns, instantaneous spanwise vortices, and time-averaged wake vortex structures. The results indicate that the vortex structure features of the flow field are significantly influenced by the arrangement type and the inclination angle of the disturbed structure. In contrast to the tandem arrangement, structures arranged in the side-by-side arrangement undergo a considerably reduced intensity of influence from aerodynamic interference effects. The blocking effect of the tandem arrangement and the channel effect of the side-by-side arrangement are undermined when the inclination angle is positive (α > 0). This study enhances the comprehension of aerodynamic interference in inclined prisms and simultaneously establishes a theoretical foundation for the wind resistance design of building structures.

Existing research on interference effects predominantly focuses on rigid structures. However, studies based on rigid models tend to overlook the feedback of structural motions on the flow field, thus failing to capture the intrinsic dynamics of the interference effect induced by wind-induced structural vibrations. This paper provides a comprehensive analysis of the fluid–structure interaction mechanisms considering interference effects involving two parallel square prisms, employing large-eddy simulation (LES). Various factors, including wind speed, arrangement, and vibration amplitude, are meticulously considered in the analysis. The study utilized three-dimensional LES simulations, incorporating the narrowband synthesis random flow generator method for inlet turbulence generation and adjusted through the “feedback” approach to ensure accuracy and efficiency. The research highlighted different structural arrangements exhibited distinct interference effects, and the end effect of the structure could substantially modify the flow pattern at various heights. In the tandem arrangements, the study observed several flow phenomena, including early reattachment, attenuation of the end effect, premature formation of roll structures, increased turbulence in the flow field due to vibration, resulting in wider second leading-edge separation, and a fragmented wake flow on the downstream structure. For side-by-side arrangements, the “acceleration effect” was identified and found to be further intensified by structural vibrations. The vibration of the interfering structure was noted to cause changes in vortex shedding frequencies and alterations in the wake flow pattern. In addition, vibration would enhance the interference effect but increasing amplitude and wind speed might diminish the interference effect. Overall, this study offers valuable insight into the intricate interplay of factors influencing the aerodynamics of parallel structures across diverse arrangements and under varying conditions.