Co-Analysis Experimentation of Synchronous Fluid-Structure Modes*

Fluid-Structure Interactions (FSI) describe the interplay between movable or compliant solids and surrounding fluid environments. Experimental FSI problems have historically been addressed through individual analyses of the fluid and structural responses in isolation, creating challenges in correlating fluid flows with associated structural dynamics.

This research presents a co-analysis procedure to visualize synchronous fluid-structure modes present in FSI. It uses Kinematic Shape Sensing (KSS), Stochastic Subspace Identification (SSI), and Spectral Proper Orthogonal Decomposition (SPOD) to identify and visualize energetic modes shared by the fluid and structural domains. The objective of this work is to use the resulting meta-algorithm to assign cause-and-effect relationship in dynamic FSI that are otherwise challenging to deduce.  

In this talk, we present an experiment consisting of a flexible beam in the turbulent wake of a circular cylinder, where it is excited by oscillatory vortices and broad-banded turbulence. KSS and Particle Tracking Velocimetry (PTV) are used to measure the beam motions and the surrounding flow simultaneously. The co-analysis procedure unambiguously separates the beam’s vibratory responses due to resonance and exogenous inputs, which are confirmed by comparison of the beam’s motion in undisturbed flow to that with a periodic excitation.