船模阻力数值水池试验不确定度评估

文章针对水面船模阻力数值水池试验,开展了不确定度分析与评估研究。不确定度分析中,验证方法和流程基于正交设计和方差分析方法,确认方法和流程基于统计推断理论。以水面船标模DTMB5415为对象,进行了船模阻力数值水池试验不确定度分析评估的实例计算,给出了对数值试验结果有重要影响的试验因素和交互作用以及各类不确定度分量的大小,并提出了降低船模阻力数值试验不确定度的建议。     

航行于波浪中的肥大型船波浪增阻计算研究(英文)

Under the background of the energy saving and emission reduction, more and more attention has been placed on investigating the energy efficiency of ships. The added resistance has been noted for being crucial in predicting the decrease of speed on a ship operating at sea. Furthermore, it is also significant to investigate the added resistance for a ship functioning in short waves of large modern ships. The researcher presents an estimation formula for the calculation of an added resistance study in short waves derived from the reflection law. An improved method has been proposed to calculate the added resistance due to ship motions, which applies the radiated energy theory along with the strip method. This procedure is based on an extended integral equation (EIE) method, which was used for solving the hydrodynamic coefficients without effects of the irregular frequency. Next, a combined method was recommended for the estimation of added resistance for a ship in the whole wave length range. The comparison data with other experiments indicate the method presented in the paper provides satisfactory results for large blunt ship.     

Comparison of the crashworthiness of various bottom and side structures

The purpose of this work is to compare the resistance with damage of various types of double bottom structures in a stranding event. The comparative analyses are made by use of a commercial, explicit finite element program. The ship bottom is loaded with a conical indenter with a rounded tip, which is forced laterally into the structures in different positions. The aim is to compare resistance forces, energy absorption and penetration with fracture for four different structures. Those four structures are: a conventional double bottom, a structure (presently protected through a patent) with hat-profiles stiffened bottom plating, a structure where all-steel sandwich panel is used as outer shell and a bottom structure stiffened exclusively with hat-profiles. The paper shows that it is indeed possible to elevate the crashworthiness of side and bottom structures with regards to the loading considered here without increasing the structural weight.     

内河船舶的浅水阻力计算

本文提供了一种估算内河船舶浅水阻力的方法。根据184条船模浅水阻力曲线及部分相应的深水阻力曲线,计算了经济航速、临界航速和不同航速下的兴波阻力系数。应用经修正的Prohaska方法计算了深、浅水形状因子。将上述这些量视为H/T、L/B、B/T和C_B的幂函数方程,应用回归分析确定其指数值。利用求得的回归公式即可进行深、浅水阻力计算,协助选择优良船型,进行主尺度分析,选配经济航速以提高营运经济性。本方法具有计算简便、适应范围广、计算精度高等优点。     

Analysis of structural crashworthiness of double-hull ships in collision and grounding

A conceptual design framework for collision and grounding analysis is proposed to evaluate the crashworthiness of double-hull structures. This work attempts to simplify the input parameters needed for the analysis, which can be considered as a step towards a design-oriented procedure against collision and grounding. Four typical collision and grounding scenarios are considered: (1) side structure struck by a bulbous bow, (2) side structure struck by a straight bow, (3) bottom raking, (4) bottom stranding. The analyses of these scenarios are based on statistical data of striking ship dimensions, velocities, collision angles and locations, as well as seabed shapes and sizes, grounding depth and location. The evaluation of the damage extent considers the 50- and 90-percentile values from the statistics of collision and grounding accidents. The external dynamics and internal mechanics are combined to analyse systematically the ship structural damage and energy absorption under accidental loadings.     

Hydrodynamic hull form optimization using parametric models

Hydrodynamic optimizations of ship hull forms have been carried out employing parametric curves generated by fairness-optimized B-Spline form parameter curves, labeled as F-Spline. Two functionalities of the parametric geometry models are used in the present study: a constrained transformation function to account for hull form variations and a geometric entity used in full parametric hull form design. The present F-Spline based optimization procedure is applied to two distinct hydrodynamic hull form optimizations: the global shape optimization of an ultra-large container ship and the forebody hull form for the hydrodynamic optimization of an LPG carrier. Improvements of ship performance achieved by the proposed F-Spline procedure are demonstrated through numerical experiments and through correlations with experimental data. The ultra-large containership was built and delivered to the ship owner. The present study validates the effectiveness of the proposed hydrodynamic optimization procedure, ushering in process automation and performance improvement in practical ship design practices.     

Study on the form factor and full-scale ship resistance prediction method

To consider the resistance component due to hull geometry, the International Towing Tank Conference (ITTC) adopted the resistance test method in 1978, introducing the form factor concept with two basic assumptions, i.e., the form factor of a model ship is the same as that of a full-scale ship and the form factor is independent of ship speed. However, it is not only very difficult to determine the form factor using the ITTC ’78 method, but also there have been questions regarding the basic assumptions. Therefore, the authors carried out three basic studies on the form factor concept and proposed a new extrapolation procedure for the prediction of full-scale ship resistance performance. The validity of the proposed procedure is being investigated by comparing sea trial and model test results. The results of this investigation will be presented in the near future.     

Verification of a simplified analytical method for predictions of ship groundings over large contact surfaces by numerical simulations

In this paper, a verification is presented of a simplified analytical method for the predictions from numerical simulations of structural performance during ship groundings over seabed obstacles with large contact surfaces and trapezoidal cross-section. This simplified analytical method was developed by Lin Hong and Jørgen Amdahl and calculates grounding characteristics, such as resistance and distortion energy, for double-bottomed ships in shoal grounding accidents. Two finite-element models are presented. One was built for a hold, and the other was built for a hold and a ship hull girder and also considers sectional properties, ship mass, added mass and the hydrodynamic restoring force. The verification was completed by comparing horizontal and vertical resistances and the distortion energy between seven numerical-simulation cases and a set of corresponding cases computed by a simplified analytical method. The results show that the resistances obtained by the simplified analytical method are close to the mean values of the resistance curves obtained by numerical simulations. The comparisons prove that the energy dissipation-prediction capability of the simplified analytical method is valuable. Thus, the simplified analytical method is feasible for assessing ship groundings over seabed obstacles with large contact surfaces and trapezoidal cross-section. Furthermore, studies of the influence of ship motion during groundings ascertained that ship motion affects structural performance characteristics. Resistances are lessened at the end of the grounding due to the reduction of indentations caused by heave and pitch motions of the ship hull girder. Finally, a new method for predicting the structural performance of the time-consuming complete-ship model by applying a combination of normal numerical simulations and ship-motion calculations is proposed and proven.     

Analysis of ship–ship collision damage accounting for bow and side deformation interaction

This paper presents a procedure to analyse ship collisions using a simplified analytical method by taking into account the interaction between the deformation on the striking and the struck ships. Numerical simulations using the finite element software LS-DYNA are conducted to produce virtual experimental data for several ship collision scenarios. The numerical results are used to validate the method. The contributions to the total resistance from all structural components of the collided ships are analysed in the numerical simulation and the simplified method. Three types of collisions were identified based on the relative resistance of one ship to the other. They are denoted Collision Types 1 and 2, in which a relatively rigid ship collides with a deformable ship, and Collision Type 3, in which two deformable ships are involved. For Collision Types 1 and 2, estimates of the energy absorbed by the damaged ships differ by less than 8% compared to the numerical results. For Collision Type 3, the results differ by approximately 13%. The simplified method is applicable for right angle ship collision scenario, and it can be used as an alternative tool because it quickly generates acceptable results.     

Behavior of a double hull in a variety of stranding or collision scenarios

A series of nine tests was conducted to investigate the behavior of a double hull in a variety of stranding or collision scenarios. Cones of five different nose radii were made to model accident scenarios ranging from grounding on a sharp rock to stranding on a relatively flat seabed or shoal, and collision with a sharp bulbous bow of a fast ship to collision with a large bow of a VLCC. Three sub-series were designed in which the cones pressed shell plating, main supporting members and intersections of main supporting members. The test results reveal that the nose radius and the location of penetration have a very strong influence on the behavior of a double hull. Therefore, careful definition of accident scenarios is of crucial importance to assess the strength of ship hulls in accidents, and it is necessary to base the assessment on probability of accidents. Characteristics of the response of structural members were identified and idealized as simple theoretical models. Analytical formulae were derived and discussed. Primary damage mechanisms include membrane stretching of shell panel, onset of rupture, crack propagation, folding of main supporting members, and crushing of intersections of main supporting members. The new plate punching model captures the phenomenon that the load-carrying capacity of a plate depends on the size of the striking object. The plate perforating model predicts the reduced strength of plates with cracks. It reflects the observed test phenomenon that loads do not drop to zero even after rupture occurs in shell plating. A simple analytical method was developed to calculate the global strength of a double hull. The method takes geometrical parameters of seabed rocks or bulbous bows into account, and can be used for a wide range of different accident scenarios. Calculations using this method compared satisfactorily with the test results. This method can be easily incorporated into a probability-based framework to properly assess structural performance for a variety of damage scenarios. Similar to the Wang et al. (J Ship Res 41 (1997) 241) paper on raking damage, which uses only four analytical models, this method also requires only a common calculator to carry out the calculations.     

双桨船Lucy Ashton轴系附体阻力的尺度效应

本文对Lucy Ashton带附体美人架和轴包架的几何相似船模试验结果重加分析。分别将带附体的和相应裸体的船模阻力试验结果绘成以C_r为纵坐标对C_F为横坐标的Froude数等值线。假定: C_r=(1 k)C_F C_W可发现全部Froude数等值线都是直线。可见三因次外插法可推广应用于带轴系附体的船模。 带轴系附体船模与相应裸体船模的1 k之差,乘以足足C_F后,可认为是轴系附体的粘性阻力系数。带轴系附体船模与相应裸体船模的C_w之差可认为是轴系附体的兴波阻力系数。以上粘性阻力系数和兴波阻力系数之和可认为是足尺轴系附体的总阻力系数。 由此三因次外插法计得的足尺轴系附体总阻力系数与由实船试验测得者间的最大误差可发现小于10％。假定船的附体阻力为裸船体阻力的10％,则最大误差小于裸船体阻力的1％。可见应用三因次外插法预估轴系附体阻力可给出十分满意的结果。     

内河双壳油船舷侧结构耐撞性分析

提出了内河双壳油船舷侧结构耐撞性能的简化分析方法,详细讨论了球鼻艏撞击作用下内河双壳油船舷侧结构的总体破坏模式及其渐进破坏过程.在考虑舷侧外壳板发生断裂破坏后的剩余抗撞能力的基础上,给出了双壳舷侧结构的撞击力―撞深曲线和吸收能量-撞深曲线,并与有限元仿真分析结果进行了比较.简化分析方法得到的结果与有限元分析基本上是一致的,这表明该方法能对内河双壳油船结构的耐撞性能做出合理预报,可用于这类油船耐撞性能的评估.     

基于CFD与三因次法结合的低速多用途船的阻力预报

为了实现对低速多用途船舶的阻力性能进行准确预报,提出将基于CFD的数值模拟与三因次法相结合的总阻力预报方法,采用Solidworks三维软件对某低速多用途船进行三维建模,依据Gambit软件对模型进行流域划分和网格划分,应用CFD理论选取合理的湍流模型和求解方法进行数值模拟计算,得到对应航速下船模的总阻力值系数,根据普鲁哈斯卡假设和三因次方法,利用最小二乘法拟合形状系数,进而计算出实船的总阻力,并且分析数值模拟的速度云图.最后与传统阻力估算方法-艾亚法进行比较,说明本文采用的阻力计算方法是可行性,给今后低速多用途肥大型船的阻力研究提供借鉴.     

舰船搁浅应急计算方法

根据舰船静力学原理提出搁浅而未破舱情况下的有关搁浅部位与海底的摩擦力以及搁浅位置确定的应急计算算法；该应急算法对快速处置搁浅具有较高的应用价值，同时为搁浅自动判析系统的研制提供了合理数学模型。     

基于离差最大化方法的船舶操纵性综合评价

将离差最大化方法应用到船舶操纵性综合评价中,引入加权向量和规范化决策矩阵,考虑各个操纵指标的权重和规范化决策矩阵对操纵性评价的影响,建立船舶操纵性综合评价体系,阐述该方法的构造原理和操作步骤。选取两个试验船模作为评价对象,以回转角速度、相对回转直径、初转期、第一超越角和第二超越角作为操纵性评价指标,分别求取两船模的操纵性评价指标的加权向量和规范化决策矩阵,并对计算得到的综合评价指标进行了分析,其结果与船模K,T,P指数一致,可以将离差最大化方法用于船舶操纵性综合评价中。     

Fourier NUBS method to express ship hull form

This article presents a method of numerical expression to draw ship hull forms. Recent developments in research into ship hull optimization need a method to express ship hull form as precisely as possible with a small number of design parameters. This method is based on a combination of the Fourier–sine series expansion and nonuniform B-spline (NUBS) interpolation. The merit of the combination is that it removes the wiggles which are often found when generating a rectangular-type curve, such as the midship section of tanker ship, with a simple Fourier series expansion. Here, the procedure is explained, and then a tanker ship hull is generated. Through the discussion, we show the effectiveness of the method.     

A simplified analytical method for estimating the crushing resistance of an inclined ship side

This paper provides a new contribution to the simplified analytical treatment of collisions between two ships. It is directly connected to the well-known super-elements method, which is a simplified procedure allowing for a quick estimation of the damages caused to both the striking and struck vessels during such events. In this article, a new analytical formulation is presented for estimating the impact resistance provided by inclined ship side panels. Two different scenarios are treated. We first deal with the case of an impact between the oblique plate and the stem of the striking ship, and then we consider the situation where the inclined panel is impacted by the bulb. For these two scenarios, an analytical formulation relating the force and the penetration is provided and these developments are validated by comparing them to the results of finite elements simulations. Finally, the new inclined plate super-element is integrated in a simplified model of a frigate collided by another ship, and the resistance given by the super-elements method is then compared to the one obtained by a numerical simulation of this collision.     

基于模板的船舶消防设计

介绍了模板及其在工程设计领域的应用情况。分析船舶消防设计的特点 ,研究了基于模板进行船舶消防设计的具体方法 ,并以AutoCAD 2 0 0 0为平台 ,开发了相应的程序。初步的研究表明 ,该方法能够较大地提高设计效率 ,并减少失误。