Fluid-Structure Interaction Analysis and the Detection of Wind Induced Vibration of Triangular Lamella

The use of very thin, subtle and light structures as an external part of buildings causes many problems related to wind induced vibration. Constructions of this type occur mostly as a part of roofs or design facades. The principal idea of this paper is to show dynamic response of triangular lamella exposed to wind gusts, which frequency is equal to the first natural frequency of the lamella. By the two-way software fluid-structure interaction (FSI) analysis, oscillation of the lamella was detected. The solution of two-way FSI analysis requires co-simulation between computational fluid dynamics and structural mechanics. In the simulation, it was essential to simulate conditions that if met, create resonant vibration of the lamella caused by vortex shedding on the leeward side of the structure. If the frequency of vortex shedding matches the resonance frequency of the structure, the structure begins to resonate and vibrates in harmonic oscillations driven by the energy of the flow. In this case, vibration rises and structure can be damaged or deformed permanently. For the long-term vibration, fatigue stress and subsequently fatigue failure is significant. By the usage of empirically derived equations, input data for the software simulation were obtained. It was important to consider mainly natural frequency of lamella, frequency of vortex shedding behind the structure and also correct properties of air such as wind speed, frequency of wind gusts, density of an air and Strouhal number. As a conclusion, dynamic response of lamella in the form of deformation and wind stream pattern depending on time is shown. It has been also shown that if the inputs are specified correctly to software simulation it is possible to analyse time history of many variables such as deformation, wind speed, and acceleration. By this method, it is possible to determine not only the maximum variables such as deformation or wind speed, but also its entire time history. In practice, it is therefore possible to create different design situations and, on their basis, design the lightweight non-bearing structures exposed to the wind. (paper)