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随机波中船舶参数横摇研究 总被引:2,自引:0,他引:2
针对随机波中船舶参数横摇,提出一种数值预报方法。采用新的随机波成形方法,求解出船舶无横倾时在随机波中时间序列垂荡和纵摇运动,确定出船-波相对位置。利用3个坐标系之间的转换关系确定船体各横剖面左右舷与波面瞬时交点,然后对波浪压力沿船长湿表面积分,得出船舶复原力的Froude-Krylov部分。提出复原力之辐射力和绕射力部分和横摇角的非线性假定。确定一个参数横摇数学模型,实现随机波中参数横摇计算;通过试验和数值模拟对一艘巴拿马型集装箱船进行了参数横摇预报,研究了随机波中参数横摇的实际非各态历经的特点。 相似文献
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High speed catamarans are used for pleasure, racing as well as passenger transportations. Optimal design of these crafts requires knowledge of sea loads exerted on their structures. The total load may be estimated by integration of loads exerted on a series of two-dimensional sections along the hull. In order to access the cross-sectional loads, the problem may be simplified to solve the water-entry problem of a twin hull. In this paper, water-entry problem of a twin wedge at constant vertical water-entry speed is studied. The problem is solved in the framework of potential theory using boundary element method where gravity effect on the flow is neglected. A simplified model based on Wagner theory is employed. Free surface elevation and pressure distribution on the body in different deadrise angles have been evaluated. A parametric study has been done to investigate effects of deadrise angle, distance between demi-hulls and free surface elevation on maximum pressure coefficient. Finally, a regression formula for maximum pressure coefficient has been proposed. Results of parametric study reveal that as time advances the interaction between two demi-hull gets more severe, besides the interaction effect on pressure coefficient is nonlinear. 相似文献
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国际海事组织(IMO)船舶设计建造分委会(SDC)第4次会议把参数横摇稳性直接评估提上议程,如何准确预报和评估不规则波中的参数横摇是亟待解决的问题。文章提出采用一种三维时域面元法进行不规则波中参数横摇的预报和评估,该方法首先采用混合源法,即在内域采用Rankine源,在外域采用瞬态的时域Green函数,该混合源法充分考虑了船体的定常和非定常运动,以及定常运动对非定常运动的影响;其次考虑了船体与不规则波浪的瞬时相对位置,沿船体瞬时湿表面进行压力积分求解Froude-Krylov力和静水力;然后通过时域求解垂荡—纵摇—横摇三自由度耦合方程计算参数横摇。文中以国际标模C11集装箱船为研究对象,研究了不同随机波浪谱下参数横摇的发生规律,进行了统计分析,并通过已有的试验结果验证了文中采用方法的有效性。结果表明,该文采用的三维时域面元法可有效用于顶浪不规则波中参数横摇的直接数值预报。 相似文献
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随着在滩涂之上建设人工沙滩的举措逐渐增多,人工沙滩剖面横向输沙研究有非常重要的现实意义。在与海岸动力相互适应的原岸滩上建造人工沙滩是较为复杂的问题,并且实际工程中的人工沙滩还受到工程措施的影响,剖面形态较难预测。在原海滩上建造人工沙滩较复杂,它适应了海岸的力量;实际工程中的新滩受工程测量的影响,因此其剖面形状难以预测。针对这个问题,采用物理模型试验的方法,针对受挡沙坝及护岸限制的人工沙滩剖面在不同水位及波浪条件下的形态变化进行试验研究,并应用工程中常用的平衡剖面模型对相对稳定的剖面进行计算比较,得出了形成稳定的剖面形态所需要的条件。试验结果验证了初始岸滩坡度1∶15的适用性,得出了当波浪受结构物影响较小时可以形成均衡沙滩剖面的结论。 相似文献
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In this paper, the dynamic responses and energy dissipation characteristics of polyvinyl chloride (PVC) foam core sandwich plates under ice impact are investigated. The ice impact tests of PVC foam core sandwich plates were conducted by employing the horizontal impact experimental apparatus. The finite element simulations were conducted to analyze the dynamic response of PVC foam core sandwich plates based on soil and concrete material model for ice impactor. It was demonstrated that numerical results were in good agreement with experimental results. The deformation modes of the top facesheets were coupling of local indentation with global bending deformation, while the deformation modes of bottom facesheets were overall bending deformation. The permanent deformation of face sheets show that the impact resistance of sandwich plate is better than that of equivalent weight hull plate (EWHP). In addition, based on the actual navigation environment of ship, the effect of impact angle and ice floe shape on dynamic response and energy dissipation are analyzed. 相似文献
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对舰船用大型水幕进行了防火分隔效果的试验研究和模拟计算,证明水幕能有效阻止火灾蔓延,降温隔热效果明显。试验验证了舰船水幕防火分隔的可行性和有效性,影响水幕防火分隔效果的主要因素是水幕用水量、厚度以及水幕水滴的直径,结果对舰船水幕防火分隔设计具有重要的参考作用。 相似文献
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In the present study, aiming to provide practical guidance for the structural design, the effects of the small bottom and sidewall stiffeners on sloshing loads in shallow and intermediate liquid conditions are investigated numerically. The interaction between the highly nonlinear free surface flow and a large number of small stiffeners is modeled based on the Moving Particle Semi-implicit method. 2D models of a rectangular clean tank and tanks with small sidewalls or bottom stiffeners are considered. For filling ratios ranging from 5% to 20%, harmonic angular motions with periods around the analytical sloshing resonant ones are applied. Simulation snapshots and computed pressure time series, pressure variation, wave run-up, maximum fluid velocity, and kinetic energy were provided to clarify the complex interaction between the small baffles and the shallow free surface flow. As a result, except for the tanks with bottom stiffeners in shallow liquid conditions, in which the response under actual resonant frequency should be considered, the response computed using the clean tank excited by its resonant period can be adopted as a conservative estimation for the sloshing loads of actual tanks with small stiffeners. 相似文献
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文章研究了多蛋形交接耐压壳屈曲行为。基于壳体开孔处的变形量与完整壳体一致的设计理念,优选多蛋壳结构参数,制作多蛋壳比例模型,并对其制作误差进行了检测。此外,还进行了静水压力试验,验证真实多蛋壳破坏形式,检验环肋参数的合理性,比较了考虑真实形状和厚度的非线性有限元分析结果。结果表明:基于变形协调理念设计的多蛋壳,最终破坏远离环肋交接处,蛋形壳单元破坏形式及载荷与完整单蛋壳基本相同,试验验证了多蛋壳继承了完整蛋形壳较好的耐压特性;基于弧长法的数值计算与试验结果具有良好一致性,考虑真实形状和厚度的非线性有限元分析可用于分析预测真实壳体的屈曲特性。 相似文献
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小面积掩护水域波浪物理模型与数学模型对比研究 总被引:2,自引:2,他引:0
通过物理模型和数学模型2种研究手段,对印度尼西亚PLTU2 JAWA BARAT 3×350 MW电厂码头工程波浪传播进行对比研究,分析港内外波高和波浪增水引起的水平面的变化。结果表明:对港内波高的分布情况数学模型模拟结果和物理模型试验结果基本吻合,从物理模型试验结果分析得出港内存在水平面的上升情况,MIKE21的BW波浪数学模型不能模拟波浪增水。分析了长周期波引起港内波浪共振的条件,港口的自振周期远远大于试验波要素的周期,故在此波浪作用下不会引起港内的共振。 相似文献
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Locally pitted tubular members are usually considered as stub columns to assess the ultimate strength. However, it is not suitable for those with relatively larger slenderness ratios as their failure behavior is more complex and closely related to corrosion features of localized pitting. This paper presents compressive column tests on locally pitted tubular members of a moderate slenderness ratio. Corrosion pits were artificially introduced on local surface of the members, forming corrosion patches with various corrosion features. A numerical modelling method was proposed to reproduce the test specimens. Localized pitting damage was proven to cause substantial declines in the load deformation capacity and ultimate strength, and have a significant effect on the failure mode. The failure of a pitted member is mostly initiated by local buckling after yielding occurs in the corrosion patch, concurrent with pitting closure, and even shear cracking of member wall due to the perforated pits. Moreover, shape change of the corrosion patch most likely results in the failure mode to alter from column buckling to local buckling or interactive buckling. The shape ratio of the corrosion patch is one of the critical factor to influence the ultimate strength of locally pitted members. The proposed modelling method is applicable for extensive stochastic simulations so as to develop an empirical formula and to clarify the probabilistic characteristics of ultimate strength. 相似文献
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以实尺度制作了疲劳试验的试件,对45000DWT江海直达散货船船底纵骨与水密及非水密实肋板连接处进行了双轴恒幅循环载荷下的疲劳试验,记录了热点处的疲劳裂纹扩展长度和对应循环次数,获得船底纵骨疲劳特性;根据不同节点处裂纹萌生和扩展情况,得出非水密节点处是疲劳危险处;用动态应变仪记录热点处的应变,根据新版《船体结构疲劳强度指南》中的热点应力法计算热点应力,用试验数据拟合了一条S-N曲线,与指南提供的D曲线进行了对比分析,验证了D曲线的合理性。同时用MSC.Patran软件建立有限元模型,选取2007版《船体结构疲劳强度指南》中名义应力法对应结构形式的F曲线,用MSC.fatigue模块计算了相应节点的总疲劳寿命,将有限元结果和试验结果进行对比,验证了热点应力法的准确性。 相似文献
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In oil and gas transportation, the compliant vertical access riser (CVAR) system conducts economic and operational advantages due to its special configuration. In this paper, the static performance of the CVAR is studied by an efficient numerical method. According to the unique configuration of the CVAR, the mathematical model is established based on minimum total potential energy principle. The equilibrium equations are discretized by finite difference method and then solved by Newton-Raphson technique. The accuracy of the numerical method is verified by OrcaFlex software. Detailed parametric analysis is carried out based on practical engineering requirements. The effects of buoyancy section's configuration including buoyancy factor, buoyancy section's length and buoyancy section's location, and external environmental factors including wellhead offset distance, water depth and current velocity on installation shape and mechanical properties of the CVAR are analyzed. The research shows that the presented numerical method has good applicability and flexibility for the early installation configuration design of marine risers which have no touchdown section but only one touchdown point and are equipped with multiple buoyancy blocks subjected to forces of different directions and magnitudes, such as CVARs. 相似文献