Flow Estimation Using Cross-Flow-Induced Vibration

Abstract

Flow passing around an object can create vertices behind it and static and dynamic pressure variation across it. Due to the dynamic pressure variation, the object/beam will be getting excited and vibrate. The major excitation frequency due to flow depends upon the flow velocity. The frequency range of excitation depends upon the type of flow regime (i.e., laminar or turbulent). When flow passes through, the beam is not only subjected to induce vibration, it will also damp the vibration and is also proportional to the flow velocity. In this paper, vibration induced on cantilever beams subjected to cross-flow is studied by numerical methods and by experiments. Vibration response of the cantilever beam at the free end is measured, using underwater accelerometer, and reported as waterfall spectrum and overall rms values. Recorded data are further analyzed in power spectral density (PSD) scale and amplitude at its fundamental frequency. It was done in three geometric configurations of beams with thirteen flow rates at each. For numerical simulation, ANSYS fluid and structural analysis package are used and results are reported. Close correlation in vibration levels is observed between the experiment and predicted results. Experimental values are plotted with polynomial regression curve for various flow velocities and acceleration levels. Obtained R2 values are better than 0.99 for two samples and for one sample it is in the order of 0.95. In all the analysis methods, i.e., PSD, amplitude at fundamental frequency and overall rms value, same order of, R2 values are obtained and repeated.