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Title: Experimental Fluid-Structure Interaction of Airflow Over a Cylinder with an Attached Cantilever Plate in a Wind Tunnel

Abstract: The phenomenon of fluid-structure interaction (FSI) is prevalent in many engineering fields, including aerospace and civil structures, maritime applications, and flow control problems. This novel study examines the FSI of a stiff cantilever plate attached to a cylinder in an AEROLAB Educational Wind Tunnel under airflow excitation. First, a comprehensive analysis of the structure's vibration modes sans airflow is performed. A detailed computer-aided design model and the finite element analysis (FEA) modal simulation are introduced. A roving hammer, accelerometer-based experimental modal analysis (EMA) method and a non-contact, full-field, high-speed digital image correlation (DIC)-based operational deflection shape (ODS) analysis method are thoroughly discussed, and the first seven out-of-plane mode shapes and operational deflection shapes are captured. The modal assurance criterion (MAC) values along the diagonal are 84.5% or greater between the EMA and FEA, 72.8% or greater between the ODS analysis and FEA, and 50.5% or greater between the EMA and ODS analysis. The natural frequency percent differences are less than or equal to 4.731% for the EMA and FEA, 3.365% for the ODS analysis and FEA, and 3.437% for the EMA and ODS. Next, 37 accelerometers are mounted to the structure, and an EMA is performed using a single hammer impact location to determine the first seven out-of-plane mode shapes. A constant temperature anemometry experiment is performed at free-stream velocities of 10, 20, and 30 m/s with 48 measurement locations. The captured data allows for visualization of the mean velocity, and a frequency domain analysis identifies the vortex shedding frequencies. An operational modal analysis (OMA) is performed and excellent correlation between the EMA and OMA mode shapes is observed, with MAC values along the diagonal greater than or equal to 96.723%, 95.293%, and 97.411% for the 10, 20, and 30 m/s cases, respectively.

Excellent agreement between the natural frequencies captured between the methods is achieved, with percent differences less than or equal to 1.158%, 2.480%, and 3.373% for the velocities tested. Lastly, using a transfer function and its coherence function, the airflow excitation is observed to have a causal relationship with the vibration response at a point on the plate.