Combining constant temperature anemometry and modal analysis for the experimental investigation of fluid-structure interaction of airflow over a cylinder with an attached cantilever plate

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 (EWT) under airflow excitation. The 37 accelerometers mounted to the structure are considered to be part of the structure itself, and an experimental modal analysis (EMA) is performed using a single hammer impact location to determine the first seven out-of-plane natural frequencies and mode shapes, where the results are shown to validate the finite element analysis (FEA) modal analysis. A constant temperature anemometry (CTA) experiment is performed at a free-stream velocity of 30 m/s with 48 measurement locations. The captured data allows for visualization of the mean velocity and turbulence intensity, and a frequency domain analysis at 24 measurement locations identifies the vortex shedding frequencies. Additional test results are provided for velocities of 20 m/s and 10 m/s. An operational modal analysis (OMA) is performed at an airflow velocity of 30 m/s and excellent correlation between the EMA and OMA mode shapes is observed, with modal assurance criterion (MAC) values along the diagonal greater than or equal to 97.41%. Excellent agreement between the natural frequencies captured between methods is achieved, with a percent difference of 3.384% or less. Lastly, using a transfer function and its coherence function, the airflow excitation is observed to partially correlate with the vibration response at a point on the plate.