Damping forces on a cylinder oscillating in a viscous fluid

Abstract

To study the damping crisis encountered in offshore structures composed of circular members, the damping forces acting on a harmonically oscillating circular cylinder were determined. An experimental setup, in which representative values of the shear-wave number together with a sufficient amplitude-to-diameter ratio can be met is very difficult to realize. This might explain the lack of experimental data so far.

Oscillating cylinder in viscous fluid: calculation of flow patterns and forces

“…These include [6] and one of the data sets by Johanning [28]. The same has been found in an unpublished experimental data set for β = 20000 (JR Chaplin (2010), personal communication), and also in other computational attempts than those presented here (JR Chaplin (2010), personal communication).…”

“…We note a fundamental difference between U-tube experiments such as those performed by Sarpkaya [5]-oscillating the water while keeping the cylinder fixed, and the experiments by Otter [6]-keeping the water at rest, oscillating the cylinder: it may be speculated if the input oscillatory channel flow gets polluted by turbulence in the former experiments. Present simulations fit well to the experiments by Otter.…”

“…This has, however, not been found in experiments with a smooth cylinder oscillating in still water. With β = 61400, Otter [6] showed that the damping forces are close to the Stokes-Wang solution for K < 1.88 and that the drag coefficient then increases for larger K because of flow separation at the cylinder. In Otter's experiment, theoretical instability value of transition to Taylor-Görtler instability [4] occurred at a Keulegan-Carpenter number of 0.37.…”

“…Chaplin and Mouazé [11] have presented a collection of available experimental measurements of the drag coefficient for 100 < β < 2×10 6 and K (about) below the theoretical stability bound of Taylor-Görtler vortices given by Hall [4]. Experiments by Otter [6] and one of the data sets by Johanning [28] exhibit drag coefficients corresponding to the Stokes-Wang solution (JR Chaplin (2010), personal communication).…”

“…Experiments by Otter [6] and one of the data sets by Johanning [28] exhibit drag coefficients corresponding to the Stokes-Wang solution (JR Chaplin (2010), personal communication). This is also true for parts of the data set of Sarpkaya [5].…”