For structures surrounded by or subjected to flow, there is generally an interaction between fluid dynamics and structural mechanics, the intensity of which can vary greatly depending on the problem. In cases of significant interaction, a fully bidirectional coupling (modeling level S4) is required, considering both directions of the interaction. With a sufficient understanding of the phenomenon, this complex coupling can be simplified through appropriate physical assumptions. Such simplification results in a one-sided fluid-structure response (modeling level S3), where the feedback effect on the flow is neglected. The validity of these simplified models must always be evaluated in the context of the specific phenomenon and, if necessary, validated through comparisons with more complex approaches.
In reduced modeling (modeling level S3), the structural response is typically determined using quasi-static wind coefficients, considering the time-varying inflow and structural deformations. Further simplifications are possible, such as using time-invariant wind loads through quasi-static wind coefficients. The choice of modeling approach depends significantly on the type and strength of the physical interaction between wind flow and structural behavior.
