Assessment of discrete wind gust parameters: Towards the worst-case scenario of a FSI application in form of an inflated hemisphere

Abstract

The paper is a step towards the evaluation of the worst-case scenario caused by strong wind gusts impacting civil engineering air-inflated lightweight structures. These extreme events with short durations but high strengths are responsible for short-term highly instantaneous loads endangering the structural integrity of the design. For this purpose, a generic test case is defined which includes a discrete wind gust model, the approaching turbulent boundary layer and a flexible structure exposed to the resulting fluid flow. The simulation framework relies on a partitioned coupled solver for fluid–structure interaction extended by two source-term formulations which allow to inject the wind gusts as well as the background turbulence. To save CPU time, a part of the investigations is conducted for the rigid case as a physical meta-model. The particularly critical cases found in this way were examined for the case of the flexible structure. Under varying system parameters such as the strength, length and position of the gust the following objective functions are evaluated: Force coefficients, maximal deflections and local inner stresses. The worst case occurs for maximal gust strength and length, when the gust hits the membrane at half height. Furthermore, the effect of the superposition of the discrete gust with background turbulence is analyzed for two scenarios. The gust is first superimposed to different inflow turbulences of the same intensity leading to non-negligible deviations of force coefficients and deflections. Second, the level of the turbulence intensity is successively increased up to a factor of five showing only a minor effect on the flexible structure not generating a new worst case.