An Investigation of a Fundamental Mechanism Controlling Interaction Between Sheared Fluid FLow and Slender Cylinders

海洋缆索和系缆涡激运动的控制机制是海洋工作者非常感兴趣的问题。在几乎所有的海洋应用中，引起运动的流体由于局部电流的变化而被剪切，或者由于电缆的曲率而被有效地剪切。剪切流使拖缆的振幅响应受到行波的调制。我们将研究切变流作用下系绳中影响调幅行波形成的基本机制。实验将在被强迫以调制运动振荡的圆柱体上进行，同时测量圆柱体的运动、作用在圆柱体上的力以及流体力的幅度和相位。这种信息的一个应用是预测长缆索上的力。该实验将包括对圆柱体周围的二维流动的数值计算，该圆柱体被强迫以调幅运动振荡。实验测量和数值计算的结合应有助于更好地理解剪切流和细长圆柱体的相互作用。

The mechanism controlling vortex-induced motion of marine cables and tethers is of great interest to those who work in the ocean. In almost all marine applications, the fluid flow, which induces themotion, is sheared due to local current variations or is effectively sheared due to curvature of the cable. Shear flow causes the amplitude response of a tow cable to be modulated by a traveling wave. The basic mechanism affecting the formation ofamplitude-modulated traveling waves in a tether subjected to a shear flow will be investigated. Experiments will be performed on a cylinder that is forced to oscillate with a modulated motion, measuring simultaneously the motion of the cylinder, the forces acting on the cylinder, and the amplitude and phase of the fluid forces. One application of such information is in the prediction of the forces on long cables. The experimental will include numerical calculations of two-dimensional flow around a cylinder that is forced to oscillate with amplitude-modulated motion. The coupling of experimental measurements and numerical calculations should lead to an improved understanding of how shear flows and slender cylinders interact.