Spatiotemporal mode extraction for fluid–structure interaction using mode decomposition

A fluid–structure interaction (FSI) analysis model was developed based on the partitioned coupling approach. The study analyzed the fluid and structure behavior in a well-established validation case known as the Turek–Hron FSI benchmark test. This test involves strong, unsteady interaction between fluid flow and an elastic flap behind a rigid cylinder. Comparison of the elastic flap displacement frequencies and amplitudes from the present FSI model with reference data showed good agreement, validating the model. Dynamic mode decomposition (DMD) was employed to extract fundamental structures from the complex spatiotemporal data obtained from the FSI analysis. In addition, a mode–sensing technique based on a greedy algorithm was developed, and significant modes were extracted with elastic flap displacement as a feature. The crucial modes for the elastic flap displacement were the second bending modes at specific frequencies. However, these results differed significantly from the natural frequencies of the second bending modes obtained via eigenmode analysis. This discrepancy can be attributed to the close coupling between the fluid and structure, which alters elastic deformation behavior. The study demonstrates the potential for straightforward extraction of essential fluid–structure coupling using FSI-DMD.