Sparse Modal Decomposition Method Addressing Underdetermined Vortex-Induced Vibration Reconstruction Problem for Marine Risers

When investigating the vortex-induced vibration(VIV)of marine risers,extrapolating the dynamic response on the entire length based on limited sensor measurements is a crucial step in both laboratory experiments and fatigue monitoring of real risers.The problem is conventionally solved using the modal decomposition method,based on the principle that the response can be approximated by a weighted sum of limited vibration modes.However,the method is not valid when the problem is underdetermined,i.e.,the number of unknown mode weights is more than the number of known measurements.This study proposed a sparse modal decomposition method based on the compressed sensing theory and the Compressive Sampling Matching Pursuit(Co Sa MP)algorithm,exploiting the sparsity of VIV in the modal space.In the validation study based on high-order VIV experiment data,the proposed method successfully reconstructed the response using only seven acceleration measurements when the conventional methods failed.A primary advantage of the proposed method is that it offers a completely data-driven approach for the underdetermined VIV reconstruction problem,which is more favorable than existing model-dependent solutions for many practical applications such as riser structural health monitoring.

混合多策略改进的斑点鬣狗优化算法及应用

针对基本斑点鬣狗算法求解精度低、易陷入局部最优值等缺点,提出一种混合多策略改进的斑点鬣狗优化算法。通过Fuch混沌映射实现鬣狗种群的多样性,利用自适应惯性权重平衡斑点鬣狗算法的全局搜索和局部开发能力,引入拉普拉斯算子进行动态交叉操作,提高SHO算法跳出局部最优的能力,将小孔成像反向学习和逐维反向学习机制相结合,使种群更符合迭代规律,提高算法的收敛速度和寻优能力。通过若干基准函数的仿真实验进行比较,其结果表明,LPSHO具有更优越的寻优性能。将改进后LPSHO运用在机械优化设计和桁架结构优化工程问题上,与其它算法对比进一步表明LPSHO能够很好解决这类结构优化问题。

Passive Control of Flow-Induced Vibration(FIV)by Helical Strakes for Two Staggered Flexible Cylinders

Helical strake is a widely-used device for passive flow-induced vibration(FIV)control of cylindrical structures.It is omnidirectional and can effectively reduce FIV response amplitude.Studies on the passive FIV control for cylindrical structures are mainly concerned with a single isolated cylinder,while the influence of wake interference between multiple cylinders on FIV suppression devices is less considered up to now.In engineering applications,multiple flexible cylinders with large aspect ratios can be subjected to complex flow forces,and the effects of wake interference are obvious.The FIV suppression effect of helical strake of a common configuration(17.5D pitch and 0.25D height,where D is the cylinder diameter)in two staggered cylinders system is still unknown.This paper systematically studied the FIV response of multiple cylinders system fitted with the helical strakes by model tests.The relative spatial position of the two cylinders is fixed at S=3.0D and T=8.0D,which ensures the cylindrical structures in the flow interference region.The experimental results show that the helical strakes effectively reduce the FIV response on staggered upstream cylinder,and the suppression efficiency is barely affected by the smooth or straked downstream cylinder.The corresponding FIV suppression efficiency on the downstream cylinder is remarkably reduced by the influence of the upstream wake flow.The wake-induced vibration(WIV)phenomenon is not observed on the staggered downstream cylinder,which normally occurs on the downstream straked cylinder in a tandem arrangement.

船用惰性气体系统技术专利分析

考虑到惰性气体系统在油船及化学品船的货物操作及运输过程中的作用,采用Innography和Soopat知识产权分析平台,对船用惰性气体系统技术领域全球专利发展趋势、主要国家和重点研发公司的专利布局进行分析,引入专利强度指标来评价专利的价值,对比分析各公司核心技术竞争力,为未来我国船用惰性气体系统的技术发展提供战略决策依据。