Phase averaged transport in the vortex-induced oscillation of a cylinder: Experiment and modeling.

摘要

High resolution Digital Particle Image Velocimetry experiments have been conducted for the vortex-induced vibration of a circular cylinder mounted like an inverted pendulum in a water tunnel. There are two drivers for this study. The first is to advance the state-of-the-art in reduced order analytical modeling by integrating highly resolved measurements into the model development process. At the same time we advance the physical understanding of beating behavior observed in low mass-damping ratio fluid-structure interactions.; The reduced-order analytical method represented a unique application of McIver's extension of Hamilton's principle to extend flow problems. Phase-averaged time-resolved measurements of terms in the integral kinetic energy transport equation have been used to generate fluid forcing functions. Experiments were conducted for a 2.54cm cylinder at a Reynolds number of 2400.; The analytical cylinder oscillation response has been obtained with the processed experimental input. A frequency and amplitude comparison has been made between the modelled response and the cylinder response acquired from the cylinder amplitude and frequency measurements, which verified the feasibility of the energy-based approach. A more traditional force-based approach was also implemented with equally accurate results.; DPIV data were also used to directly examine fluid-structure interaction physics. Features of the energy transport terms have been presented. Spectral analysis of the phase-averaged energy transport data were performed. This analysis revealed a slight mismatch between the fluid kinetic energy flux and the time rate of change of fluid kinetic energy. This was interpreted as a competition between vortex shedding and cylinder oscillation frequencies which, in turn, give rise to observed beating phenomena.