Numerical Analysis of Fluid–Structure Interaction in Open and Closed Saddle-Shaped Membrane Structures: A New Framework Based on Vortex Dynamics

Abstract

The strong fluid–structure interaction (FSI) between the membrane structure and the surrounding airflow directly impacts the wind pressure distribution and structural stability, which are concerned with structural safety. This paper comparatively investigates the FSI of open and closed-type saddle-shaped membrane structures under wind loads, in terms of wind pressure distribution and flow field characteristics. First, a bidirectional FSI numerical simulation, integrated into this vortex dynamics-based framework, was implemented for the spatial membrane structure in laminar flows. The accuracy of the simulation was verified based on previous wind tunnel tests, from the perspective of both structural vibration and flow field. Subsequently, leveraging the framework's ability to track vortex evolution, a comparative analysis of wind pressure distribution and velocity trajectories was conducted for both configurations. Finally, the framework enabled a deep analysis of how vortex structures–their formation, development, and dissipation–influence structural vibration. The results indicate that the peak wind pressure coefficients of the open membrane structure at the leading edge under 0° and 90° wind directions reach 0.5 and 0.7, respectively. At a 45° wind direction, the flange area becomes a risk focus due to conical vortices. For closed membrane structures, the minimum average wind pressure coefficients under 0° and 90° wind directions were −0.52 and −1.0, respectively, with significant overall wind suction force. The open-type membrane structures exhibit both positive and negative pressure zones at all wind directions. Airflow separation results in wind pressure peaks at the leading edge of the windward side. Wind direction obviously affects the type of vortex structure, and the more sufficient vortex development would lead to increased trailing edge amplitude. Then, the local dynamic response of open-type membrane structures should be paid more attention. However, closed-type membrane structures experience upward lifting at all wind directions. The enhanced stiffness of the internal gas would reduce pulsations, and therefore the risk of structural overall instability should be considered as priorities.