Experimental Investigation for a flapping flag using coupled POD for FSI

Proper Orthogonal Decomposition has been extensively used to study complex fluid dynamic flows. However, for experimental Fluid-Structure Interaction (FSI) studies, the application of POD has been limited to fluid flow only. Goza and Colonius [JF&S:2018] developed the coupled modal analysis formulation encompassing fluid and structure together for the computational FSI studies. For this study, we used the approach provided by Goza and Colonius and developed a framework for coupled POD applied to the experimental FSI study. For this study, 2D PIV experiments were performed for flapping flags with dimensionless rigidity 4.3 x10^-3, and 2.6 x 10^-3. The flag's mass and aspect ratios were 1.47 and 0.25, respectively. The Reynolds number for this study is 6.7 x 104 and 8.7 x 104. For coupled POD analysis, the illumination of the membrane from the raw PIV images was used to estimate the structure energy for the coupled kernel. The coupled POD formulation for the FSI study was validated using synthetic data. The results demonstrated a coupling between the modes that captured the limit-cycle oscillations and observed the change in the modal energy distribution with a change in the flag oscillations.