کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
792266 | 1466585 | 2016 | 9 صفحه PDF | دانلود رایگان |
• Amplitude response of a streamwise oscillating cylinder is examined.
• Phase and amplitude of unsteady drag force estimated using equations of motion.
• No change in phase of drag force observed in low amplitude, lock-in region.
• Low amplitude region coincides with sudden drop in amplitude of unsteady drag force.
• Influence of choice of damping ratio is examined.
This brief communication examines the fluid forces acting on a cylinder free to move in the streamwise direction throughout its response regime. The amplitude and phase of the unsteady drag coefficient are estimated from the displacement signals and a simple harmonic oscillator model. We examine the counter-intuitive reduction in vibration amplitude observed in streamwise vortex-induced vibrations (VIV) at resonance, which has remained one of the most poorly understood aspects of VIV. Our results show that it is not caused by a change in the phase of the fluid forcing with respect to the cylinder displacement, as suggested by previous researchers; instead, we show that there is a sudden decrease in the amplitude of the unsteady drag coefficient in this region. The possible cause of this result, relating to three-dimensionality in the wake, is briefly discussed.
Journal: Journal of Fluids and Structures - Volume 62, April 2016, Pages 147–155