Establishing direct phenomenological connections between fluid and structure by the Koopman-Linearly Time-Invariant analysis

In this work, we introduce a novel data-driven formulation, the Koopman-Linearly-Time-Invariant (Koopman-LTI) analysis, for analyzing Fluid-Structure Interactions (FSI). An implementation of Koopman-LTI on subcritical free-shear flow over prism at Re=22,000 corroborated configuration-wise universal Koopman system, which approximated configuration's nonlinear dynamics with stellar accuracy. The also successfully decomposed entwined morphologies raw measurement into linear superposition frequency-based constituents. Most importantly, random and anisotropic turbulence, yielded frequency-wise identical modes structure response fluid excitation, thus establishing direct constitutive relations between phenomenology structure.