共查询到20条相似文献,搜索用时 9 毫秒
1.
Ince-Strutt stability chart of ship parametric roll resonance in irregular waves is conducted and utilized for the exploration of the parametric roll resonance in irregular waves. Ship parametric roll resonance will lead to large amplitude roll motion and even wreck. Firstly, the equation describing the parametric roll resonance in irregular waves is derived according to Grim’s effective theory and the corresponding Ince-Strutt stability charts are obtained. Secondly, the differences of stability charts for the parametric roll resonance in irregular and regular waves are compared. Thirdly, wave phases and peak periods are taken into consideration to obtain a more realistic sea condition. The influence of random wave phases should be taken into consideration when the analyzed points are located near the instability boundary. Stability charts for different wave peak periods are various. Stability charts are helpful for the parameter determination in design stage to better adapt to sailing condition. Last, ship variables are analyzed according to stability charts by a statistical approach. The increase of the metacentric height will help improve ship stability. 相似文献
2.
Moving-Particle Semi-Implicit Method for Vortex Patterns and Roll Damping of 2D Ship Sections 总被引:2,自引:1,他引:1
A meshless method, Moving-Particle Semi-hnplicit Method (MPS) is presented in this paper to simulate the rolling of different 2D ship sections. Sections S. S. 0.5, S.S. 5.0 and S. S. 7.0 of series 60 with CB = 0.6 are chosen for the simulation. It shows that the result of MPS is very close to results of experiments or mesh-numerical simulations. In the simulation of MPS, vortices are found periodically in bilges of ship sections. In section S. S. 5.0 and section S. S. 7.0, which are close to the middle ship, two little vortices are found at different bilges of the section, in section S. S. 0.5, which is close to the bow, only one big vortex is found at the bottom of the section, these vortices patterns are consistent with the theory of Ikeda. The distribution of shear stress and pressure on the rolling hull of ship section is calculated. When vortices are in bilges of the section, the sign clmnge of pressure can be found, but in section S. S. 0.5, there is no sign change of pressure because only one vortex in the bottom of the section. With shear stress distribution, it can be found the shear stress in bilges is bigger than that at other part of the ship section. As the free surface is considered, the shear stress of both sides near the free surface is close to zero and even sign changed. 相似文献
3.
研究有缆遥控潜水器(Remote Operated Vehicles)的脐带缆受到轴向激励所产生的大幅横向振动,即参量共振.ROV脐带缆的参激现象发生会影响ROV的安全性.针对ROV脐带缆的结构特性,推导出其在轴向激励力下的非线性振动方程.运用希尔无穷行列式的方法分析脐带缆的参量不稳定性.以稳定性图为基准分析脐带缆在多... 相似文献
4.
《中国海洋大学学报(自然科学版)》2015,(8)
为提高系统运行的可靠性以及安全性,故障检测技术已经成为很多技术流程中必不可少的部分。在系统的数学模型中,故障可分为加性故障和参数故障,参数故障是较加性故障更为复杂的一种故障类型。本文针对一类带乘性噪声的复杂系统,建立了其参数故障模型。并在传统最优滤波的基础上推导出该系统的常增益最优滤波公式,研究了参数故障在新息中的表现形式并给出了相关证明。基于故障发生前后新息序列的变化规律,本文设计了一类参数故障检测方法。仿真结果表明该方法能够及时有效的识别出故障的发生点。 相似文献
5.
Parametric rolling is one of five types of the ship stability failure modes as proposed by IMO. The periodic change of the metacentric height is often considered as the internal cause of this phenomenon. Parametric rolling is a complex nonlinear hydrodynamic problem, often accompanied by large amplitude vertical motions of ships. In recent years,the Reynolds-averaged Navier–Stokes(RANS) equation simulations for viscous flows have made great progress in the field of ship seakeeping. In this paper, the parametric rolling for the C11 containership in regular waves is studied both experimentally and numerically. In the experiments, parametric rolling amplitudes at different drafts, forward speeds and wave steepnesses are analyzed. The differences in the steady amplitudes of parametric rolling are observed for two drafts. The effect of the incident wave steepness(or wave amplitude) is also studied, and this supports previous results obtained on limits of the stability for parametric rolling. In numerical simulations, the ship motions of parametric rolling are analyzed by use of the potential-flow and viscous-flow methods. In the viscousflow method, the Reynolds-averaged Navier–Stokes equations are solved using the overset grid method. The numerical accuracies of the two methods at different wave steepnesses are also discussed. 相似文献
6.
Hyeon Kyu Yoon Nam Sun Son Gyeong Joong Lee 《Oceanic Engineering, IEEE Journal of》2007,32(4):798-806
When a fast container ship or a naval vessel turns, accompanying roll motions occur. This roll effect must be considered in the horizontal equations of the motion of the ship to predict the maneuverability of the ship properly. In this paper, a new method for determining a model structure of the hydrodynamic roll moment acting on a ship and for estimating the hydrodynamic coefficients is proposed. The method utilizes a system identification technique with the data from sea trial tests or from free running model (FRM) tests. To obtain motion data that is applied to the proposed algorithm, an FRM of a large container ship was developed. Using this model ship, standard maneuvering tests were carried out on a small body of water out of doors. A hydrodynamic roll moment model was constructed utilizing the data from turning circle tests and a 20-20 zig-zag test. This was then confirmed through a 10-10 zig-zag test. It was concluded that a model structure of the hydrodynamic roll moment model could be established without difficulty through a system identification method and FRM tests. 相似文献
7.
A boundary element method is developed for calculating the flare ship hull slammingproblem.The nonlinear free surface elevation and the linear element assumption are employed.The meth-od has been verified by comparisons with results for the water entry of wedges with various deadriseangles.Numerical results show that the pressure distribution varies greatly with the ship hull with differentcurvilinear equations,and the slamming features are also different.From the numerical simulation,the au-thors found that the structural damage of the flare hull might be caused by the increasing hydrodynamicpressure over an extensive area on the flare when the upper part of the flare comes into contact with water. 相似文献
8.
9.
Research on Design Method of the Full Form Ship with Minimum Thrust Deduction Factor 总被引:1,自引:1,他引:0
In the preliminary design stage of the full form ships, in order to obtain a hull form with low resistance and maximum propulsion efficiency, an optimization design program for a full form ship with the minimum thrust deduction factor has been developed, which combined the potential flow theory and boundary layer theory with the optimization technique. In the optimization process, the Sequential Unconstrained Minimization Technique(SUMT) interior point method of Nonlinear Programming(NLP) was proposed with the minimum thrust deduction factor as the objective function. An appropriate displacement is a basic constraint condition, and the boundary layer separation is an additional one. The parameters of the hull form modification function are used as design variables. At last, the numerical optimization example for lines of after-body of 50000 DWT product oil tanker was provided, which indicated that the propulsion efficiency was improved distinctly by this optimal design method. 相似文献
10.
随着海上交通运输业业务需求的不断增加,传统的目标检测方法已无法满足实际需求。由于卫星遥感技术的快速发展,基于合成孔径雷达(Synthetic Aperture Radar,SAR)图像舰船目标自动识别具有显著的应用潜力。近年来,深度学习技术在目标检测领域逐渐显现出优势,特别是YOLO (You Only Look Once)模型以其较高的精度和计算效率,为SAR舰船目标的识别提供了一种新的方法。为对比不同的YOLO模型在舰船目标识别领域的性能及其相比于两阶段深度学习算法的优势,本文首先对YOLO系列的结构进行了归纳总结;其次对当前广泛使用的数据集进行了对比分析,并基于SAR图像数据集(SAR Ship Detection Dataset,SSDD)的样本进行重新标注构建出本文的数据集;然后将YOLO系列模型与两阶段目标检测方法——更快速的区域卷积神经网络(Faster Region-based Convolutional Neural Network,Faster R-CNN)在SAR舰船目标检测的精度和速度两方面进行对比实验;最后在YOLOv5模型的基础上对主干网络(Backbone... 相似文献
11.
无人船测深系统被越来越广泛地应用于采集水深数据。在复杂水域环境中进行作业时,无人船受到工作底图及导航方式的限制,难以采用自动航行模式进行测绘,因此提出了一种无人机正射影像辅助无人船测深的作业方法。通过无人机快速获取测区正射影像成果,利用正射影像辅助进行测区划定和测线布设,避开可能造成作业风险的水上障碍物和岸滩。并在此基础上进行自动航行线路的规划设计,在水位不低于正射影像获取水位时开展无人船测深作业。经验证,采用该方法能够最大限度的完成测绘任务,同时降低作业强度与风险,具有较好的应用价值。 相似文献
12.
13.
14.
The maximum bending moment or curvature in the neighborhood of the touch down point (TDP) and the maximum tension at the top are two key parameters to be controlled during deepwater J-lay installation in order to ensure the safety of the pipe-laying operation and the normal operation of the pipelines. In this paper, the non-linear governing differential equation for getting the two parameters during J-lay installation is proposed and solved by use of singular perturbation technique, from which the asymptotic expression of stiffened catenary is obtained and the theoretical expression of its static geometric configuration as well as axial tension and bending moment is derived. Finite element results are applied to verify this method. Parametric investigation is conducted to analyze the influences of the seabed slope, unit weight, flexural stiffness, water depth, and the pipe-laying tower angle on the maximum tension and moment of pipeline by this method, and the results show how to control the installation process by changing individual parameters. 相似文献
15.
16.
17.
18.
根据舰船辐射噪声频域特性,从舰船辐射噪声线谱、谱密度的发展变化趋势、特征频段信号能量 3 个方面考虑,对舰船辐射噪声仿真数据和实测数据进行一致性分析,综合评估舰船辐射噪声仿真模型置信度。通过对舰船辐射噪声仿真模型置信度分析,为舰船辐射噪声仿真信号源置信度提供理论支撑。 相似文献
19.
Knowledge-Based Engineering (KBE) is introduced into the ship structural design in this paper. From the implementation of KBE, the design solutions for both Rules Design Method (RDM) and Interpolation Design Method (IDM) are generated. The corresponding Finite Element (FE) models are generated. Topological design of the longitudinal structures is studied where the Gaussian Process (GP) is employed to build the surrogate model for FE analysis. Multi-objective optimization methods inspired by Pareto Front are used to reduce the design tank weight and outer surface area simultaneously. Additionally, an enhanced Level Set Method (LSM) which employs implicit algorithm is applied to the topological design of typical bracket plate which is used extensively in ship structures. Two different sets of boundary conditions are considered. The proposed methods show satisfactory efficiency and accuracy. 相似文献
20.
张钰 《数字海洋与水下攻防》2020,3(4):314-322
为了掌握高海况下舰船的纵摇运动规律并对其进行准确预报,分析了舰船的纵摇运动规律。运用谱分析原理和频率响应法,分别在 4 级、5 级和 6 级海况下,根据海浪谱密度函数和舰船的纵摇频率响应函数,求得其纵摇运动谱密度函数;再运用公式推导,得到其纵摇运动的时域函数;使用 MATLAB 仿真软件对舰船进行纵摇运动仿真,得到 3 种高海况条件下的舰船纵摇运动时域函数图像,并验证仿真结果的准确性。 仿真结论:在高海况下,海况等级对舰船纵摇影响显著,海况等级越高,舰船纵摇的角度值范围就越大。以某型舰船为例的预报结果:在 4 级海况下,舰船纵摇的幅度在±6°之间;在 5 级海况下,舰船纵摇的幅度在± 15°之间;在 6 级海况下,舰船纵摇幅度可以达到±30°之间。 相似文献