基于时域解耦算法的多液舱浮式结构物运动模拟

张崇伟; 宁德志

doi:10.6052/0459-1879-19-210

基于时域解耦算法的多液舱浮式结构物运动模拟

大连理工大学海岸和近海工程国家重点实验室, 大连 116024

基金项目: 1) 国家自然科学基金(51709038);国家自然科学基金(51679036);中国博士后科学基金(2019T120209);中国博士后科学基金(2018M630289);中央高校基本科研业务费专项资金资助项目(DUT19RC(4)027)

详细信息

通讯作者:
宁德志

中图分类号: U661.1
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出版历程
- 收稿日期: 2019-07-29
- 刊出日期: 2019-11-17

MOTION SIMULATION OF FLOATING STRUCTURE WITH MULTIPLE SLOSHING TANKS BASED ON TIME-DOMAIN DECOUPLING ALGORITHM

State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China

摘要

摘要: 对于带有多个晃荡液舱的浮式结构物, 浮体的运动、外场水动力以及各舱内的液体晃荡力会实时相互决定, 发生复杂的耦合作用. 为准确模拟多液舱浮式结构物的运动, 本文引入一种有效的时域解耦算法. 该方法以模态分解法为基础, 通过对浮式结构物所受外域水动力和各液舱内非线性晃荡力进行模态分解, 最终形成时域解耦运动方程, 无需迭代求解过程即可显式计算浮式结构物的瞬时加速度. 该方法可避免传统迭代求解方法在迭代次数、截断误差和收敛特性等方面的不足, 减少解耦过程的计算耗时. 本文进一步结合边界元数值方法, 分别对单液舱浮式结构物和多液舱浮式结构物的工况开展数值模拟研究. 通过与单液舱浮式结构物的实验结果对比, 验证了本文时域解耦算法的有效性. 本文详细分析了晃荡力对单液舱浮式结构物运动的影响, 发现存在一个共振影响区间: 当外场波浪频率在该区间之外时, 可以在时域计算结果中观察到稳定的浮体运动; 在比该区间更低频的波况下, 液舱晃荡力与外场波浪力相位相反甚至可以相互抵消, 此时晃荡液舱的存在可以减弱浮体运动; 在比该区间更高频的波况下, 液舱内晃荡力与外场波浪力可以具有相同相位, 此时晃荡液舱的存在会加剧浮体的运动. 本文进一步研究了四液舱浮式结构物在波浪中的纵荡、垂荡和纵摇运动情况, 发现非线性液舱晃荡可对纵荡和纵摇运动产生影响, 但对垂荡运动影响很小.
- 晃荡 /
- 耐波性 /
- 流固耦合 /
- 浮式结构物 /
- 边界元
Abstract: For a floating structure with multiple sloshing tanks, the structure motion, external hydrodynamics and sloshing dynamics of liquid tanks are mutually determined with complex coupling mechanism. This study introduces an effective time-domain decoupling algorithm for an accurate motion simulation of floating structure with multiple sloshing tanks. The algorithm is derived based on the modal decomposition approach. By decomposing the external hydrodynamic force and nonlinear sloshing forces in each liquid tank of the floating structure, this study gives a time-domain decoupling motion equation. With this algorithm, the instantaneous acceleration of a floating structure at any instant is calculated explicitly without iterations. Limitations of the conventional iterative method in terms of the iteration number, truncation errors and numerical convergences can be avoided. The CPU time consumption on dealing with the coupling effects can be greatly reduced. Combined with the boundary element method, the algorithm is applied to time-domain simulations of a floating structure with either a single liquid tank or multiple tanks. For single-tank cases, the time-domain decoupling algorithm is validated by comparing with the experimental measurements. This study first analyzes effects of the sloshing dynamics on a single-tank floating structure. A specific frequency range is found, outside which the floating structure shows a steady motion in the time domain. For lower wave frequency cases around this range, the sloshing force and external wave force can be in anti-phase or even cancelled, so that the motion of the structure is weakened. For higher wave frequency cases, the sloshing force can be in the same phase with the external wave force, and the liquid sloshing can eventually amplify the structure motion. Further, a floating structure with four liquid tanks is further investigated. It shows that the nonlinear sloshing forces can affect the surge and pitch motion of the structure, but with little effect on the heave motion.
- sloshing /
- seakeeping /
- fluid-structure interaction /
- floating structure /
- boundary element

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