低应力拖缆瞬态动力学分析与实验研究(英文)

Transient Dynamic Analysis of Towed Low-tension Cable with Experimental Verification

文章进行了低应力拖缆瞬态动力学的数值分析与实验研究。在低应力拖缆的建模中,包括了几何,流体的非线性和弯曲刚度。在数值分析中,广义α时域积分法用于求解低应力拖缆的三维动力学方程。为了验证数值分析的结果,观察实际的物理现象,进行了拖曳实验。测量了低应力拖缆顶端处的张力,剪切力和拖曳过程的速度变化。稳态拖曳速度下张力和剪切力的波动及其 FFT 变换证明了涡激振动现象的存在。在瞬态过程中,对于稳态拖曳速度为 1.01,1.5 m/s情况,无论张力还是剪切力都存在一个明显过冲区域,但是这一现象在稳态速度为 0.55 m/s 时并不明显。定常系数法和变系数法被用于瞬态动力学的仿真分析,分析结果表明变系数法与实验结果具有较好的一致性。

A numerical and experimental investigation into the transient dynamic behavior of a towed low tension cable is presented. Fluid and geometric non-linearity is considered and bending stiffness terms are included to ensure a well posed problem when tension becomes very low. In the numerical study, the generalized α method is employed for solving the three-dimensional cable equations. In order to verify the numerical results and to observe real physical phenomena, an experiment was carried out for 3 m cable in towing tank. Cable tension and shear forces were measured at the top end, towed velocities were recorded as well. The tension and shear force fluctuation and their FFT spectrum under steady towed velocity demonstrate the effect of vortex shedding. During trainsient process, whatever tension or shear force, there is an overshot domain for towing velocity at 1.01m/s and 1.5m/s. However, this phenomenon does not happen at 0.55m/s. Constant coefficient method and variable coefficient method are employed to simulate transient behavior. Excellent numerical and experimental agreement is reported when variable coefficient method is employed. The solution of this problem is of practical significance in the calculation of the transient forces acting on mooring and towing lines which are subjected to arbitrarily prescribed motions.