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An immersed body boundary method is adopted to track the motions of a towing cylinder, and a homogenous multiphase Eulerian-Eulerian fluid approach is used to capture the free surface. The Reynolds average Navier-Stockes (RANS) solver is applied to all gird nodes to deal with different velocities of the nodes that are in the body boundary, near the boundary and out of the boundary and their effect on the fluid. The towing cylinder resistance at different submerged depths in the tank is presented. The simulation results are compared with the experimental data, and the method is verified and validated. Finally, the hydrodynamic characters of the cylinder are discussed further. The numerical and experimental results show that at high speeds, the deeper the cylinder submerges, the lower resistance it suffers. The resistance coefficient trough is obtained at Froude number in the range of 0.3 < F r < 0.4. These phenomena can provide some suggestions on the small waterplane area twin hull (SWATH) design. 相似文献
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介绍了基于米切尔Michell瘦船理论的一种小水线面双体船SWATH兴波阻力计算基本原理.运用敞篷函数对船体表面及流场进行了线性近似,建立了数值计算模型,对一类直/斜支柱SWATH兴波阻力进行计算,重点分析了支柱间距、倾角变化对兴波阻力的影响,并将计算结果与实验测试进行对比,二者基本吻合,证明该方法用于计算SWATH的兴波阻力是可行和有效的. 相似文献
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In the traditional method for the reliability analysis of fault-tolerant system, the system structure is described by means
of binary decision diagram (BDD) and Markov process, and then the reliability indexes are calculated. However, as the size
of system augments, the size of state space will increase exponentially. Additionally, Markov approach requires that the failure
and repair time of the components obey an exponential distribution. In this study, by combining dynamic fault tree (DFT) and
numerical simulation based on the minimal sequence cut set (MSCS), a new method to evaluate reliability of fault-tolerant
system with repairable components is proposed. The method presented does not depend on Markov model, so that it can effectively
solve the problem of the state-space combination explosion. Moreover, it is suitable for systems whose failure and repair
time obey an arbitrary distribution. Therefore, our method is more flexible than the traditional method. At last, an example
is given to verify the method. 相似文献
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传统的设计螺旋方法由于割裂了学科间耦合,得到的设计往往是满足设计要求的设计而不是最优的设计.多学科设计优化(MDO)方法正是一种能得到最优设计的新设计方法,MDO目前被广泛应用于复杂工程系统的设计中.文中对多学科设计优化的理论进行了简要综述,在此基础上为了演示MDO方法应用于舰船设计,采用iSIGHT对国外的CGX巡洋舰概念设计的13个模块进行了集成,建立了MDO模型并优化,得到了较好的优化解.在此基础上采用神经网络重新建立了该MDO模型,将优化结果和原MDO模型优化结果进行了比较. 相似文献