共查询到19条相似文献，搜索用时 156 毫秒
1.
针对已建成科考船加装中水多波束的实际技术需求,结合中水多波束加装科考船的船舶线型及其系统安装要求,通过设计两种不同类型的导流罩线型,并与船体线型一体化进行计算流体动力学(Computational Fluid Dynamics,以下简称CFD)仿真分析,了解实船舶航行过程中船体型线和导流罩型线之间的相互影响,分别对圆弧型导流罩和折角型导流罩的防气泡性能和阻力性能进行了CFD预报和分析。最后经海试验证折角型导流罩能够完全满足中水多波束的安装线型流线及湍流动能的性能指标,为科考船多波束导流罩的设计安装或加装提供一定的借鉴和参考作用。 相似文献
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基于BP神经网络的变形三体船布局优化研究 总被引：1，自引：0，他引：1
针对以DTMB5415为基础船型提出的高速可变形三体船,以CFD软件计算结果为样本值,利用BP神经网络方法对三体船静水阻力进行多次训练,在保证精度的基础上模拟预测了多组不同航速、不同布局下的单位排水量阻力值,从而得出了随航速变化下该船型可调节的适航布局。BP神经网络法较之传统CFD计算不仅能极大的缩短计算时间,而且能快速可靠的搜索到任意航速下能耗最小的布局,打破了CFD方法必须通过限定布局和航速求得阻力值来进行比较的固有模式,真正实现了三体船"可变形"的优势,工程适用性强,为计算机辅助三体船布局优化研究提供了一种新思路。 相似文献
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通过主机轴功率的测试判断船体,主机,螺旋桨三者的匹配状况 总被引：3，自引：0，他引：3
渔船主机是渔船的心脏，其技术状况的好坏直接影响到船舶的性能，而船体，主机，螺旋桨三者的匹配情况对船舶的航速，拖力以及经济效率都具有重要的影响。 相似文献
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随着我国能源需求越来越大,能源形势越来越严峻,各大班轮公司开始精耕细作,积极寻找降低运营成本的方法。以LPG型船舶为例,对船舶纵倾优化技术进行研究,符合当下节能减排的要求。传统的纵倾优化依据船模试验来分析,项目耗时长而且费用较高。运用CFX和FLUENT等商业软件计算LPG船的阻力数值,再用船模实验结果来验证,找到比较合理的数值计算方法,再对LPG船不同吃水、不同速度、不同纵倾下的阻力进行数值模拟计算。结果表明,排除水深的影响,LPG船舶在不改变船舶航速、载重量的前提下可以通过纵倾调节来减少船舶阻力,这对于LPG型船舶类似的肥大型船舶也有一定的指导意义。 相似文献
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水下拖曳航行器是被广泛应用的水下监测平台。为掌握水下拖曳航行器的水动力及其拖揽姿态，文章通过CFD仿真分析计算其零攻角下的阻力系数，并通过多刚体-球铰模型建立其运动数学模型，分析不同航速下拖曳系统的总拉力、拖缆长度和航行器位置等的参数变化。研究结果表明：随着船舶航速的变化，拖曳系统各项参数变化的差别很大；在200 m深度时，6 kn航速相比4 kn航速的总拉力增加73%，而所需的拖缆长度仅增加1%。该数学模型可对不同航速下的水下拖曳系统的总拉力和拖缆姿态等做出预测，为拖曳系统设计提供技术支撑。 相似文献
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船舶在冰区航行中,冰荷载是船舶结构设计和安全航行的重要影响因素。采用具有黏结破碎特征的离散单元法对船舶在平整冰区的航行过程进行了数值分析。在船舶破冰过程的离散元模拟中,平整冰由球形颗粒黏结而成,同时考虑了海水浮力和拖曳力对海冰单元的作用,颗粒间的黏结作用可在海冰与船体的相互作用过程中发生破碎;船体由三角形单元构造,分析了在海水浮力、推进器推力及海冰共同作用下船体的六自由度运动特性。通过船体与海冰相互作用的离散元分析,确定了船舶在破冰过程中海冰作用在船体上的冰荷载,探讨了船舶推进器推力和海冰厚度对冰荷载的影响,并与Lindqvist船体冰阻力经验公式进行了对比。 相似文献
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采用CFD方法模拟船体纵横摇工况下船舶海面风测量过程,分析船体、上层建筑造成的气流畸变以及船体摇摆对海面风测量数据偏差的影响规律,利用海上实船实验数据对仿真结果进行验证,结果表明:考虑船体摇摆工况的仿真结果更接近实验数据;船体、上层建筑对海面气流的影响不可忽略,仅通过船体姿态校正相对风测量数据是不充分的;船体纵横摇工况下测风点处平均相对风速偏差不仅与迎风角度有关,还与海况有关。随着相对风速增大,同一迎风角度条件下的平均相对风速偏差趋于稳定,船体周围瞬态气流场在时间平均后呈现雷诺数无关性。 相似文献
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潜艇指挥台围壳对阻力和伴流场影响数值研究 总被引：2，自引：0，他引：2
采用Reynolds平均Navier-Stokes(RANS)方法计算潜艇三维粘性流场,分析潜艇指挥台围壳对潜艇水动力性能的影响.采用全附体SUBOFF模型验证了CFD方法,通过将螺旋桨盘面处的实效伴流场、艇体表面压力分布以及模型总阻力的模拟结果与Taylor船池的实验结果进行对比.比较结果显示CFD计算结果与实验数据具有很好的一致性,表明CFD方法可以用于潜艇指挥台围壳设计的水动力计算.通过数值计算研究指挥台围壳的高度和在艇上的分布位置对其后方的流场、螺旋桨盘面处的伴流场和阻力的影响. 相似文献
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船体曲面几何表达及水动力性能计算的NURBS方法 总被引：1，自引：1，他引：0
采用非均匀有理B样条(NURBS)对船体曲面形状进行几何表达,所生成的网格直接用于后续的有关船体水动力性能计算工作中。对Wigley船型的线性兴波阻力和斜航操纵运动的船体,结合近似的Kutta条件作了相应的数值计算,从与试验结果的比较来看,该方法具有较好的工程精度,对船舶及海洋工程领域中的计算机辅助设计(CAD)与计算流体动力学(CFD)之间的相互集成,具有推动与促进作用。 相似文献
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Increasing propulsion efficiency, safety, comfort and operability are of the great importance, especially for small ships operating on windy sites like the North Sea and the Baltic Sea. Seakeeping performance of ships and offshore structures can be analysed by different methods and the one that is becoming increasingly important is CFD RANS. The recent development of simulation techniques together with rising HPC accessibility enables performance of advanced seakeeping simulations for ships in a full scale. The paper presents CFD seakeeping analysis for a case study vessel in two variants: V-shaped bulbous bow hull form (as built) and innovative hull form (X-bow type). The study presents the influence of redesigning the ship on selected seakeeping aspects. The advanced CFD model, with the application of overset mesh technique, was described in detail. Selected numerical results were validated on the basis of experimental testing in a towing tank and showed good agreement. The approach demonstrated here of performing the CFD seakeeping simulations for the analysis of ship performance in a full scale and close to real loading conditions has direct application to the design process as well as in determination of optimal operational parameters of any ship. 相似文献
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This paper proposes a Computational Fluid Dynamics (CFD) based unsteady RANS model which enables the prediction of the effect of marine coatings and biofouling on ship resistance and presents CFD simulations of the roughness effects on the resistance and effective power of the full-scale 3D KRISO Container Ship (KCS) hull.Initially, a roughness function model representing a typical coating and different fouling conditions was developed by using the roughness functions given in the literature. This model then was employed in the wall-function of the CFD software and the effects of a typical as applied coating and different fouling conditions on the frictional resistance of flat plates representing the KCS were predicted for a design speed of 24 knots and a slow steaming speed of 19 knots using the proposed CFD model. The roughness effects of such conditions on the resistance components and effective power of the full-scale 3D KCS model were then predicted at the same speeds. The resulting frictional resistance values of the present study were then compared with each other and with results obtained using the similarity law analysis. The increase in the effective power of the full-scale KCS hull was predicted to be 18.1% for a deteriorated coating or light slime whereas that due to heavy slime was predicted to be 38% at a ship speed of 24 knots. In addition, it was observed that the wave resistance and wave systems are significantly affected by the hull roughness and hence viscosity. 相似文献
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The homotopy method is utilized in the present inverse hull design problem to minimize the wave-making coefficient of a 1300 TEU container ship with a bulbous bow. Moreover, in order to improve the computational efficiency of the algorithm, a properly smooth function is employed to update the homotopy parameter during iteration. Numerical results show that the homotopy method has been successfully applied in the inverse design of the ship hull. This method has an advantage of high performance on convergence and it is credible and valuable for engineering practice. 相似文献
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In order to reduce the total resistance of a hull, an optimization framework for the bulbous bow optimization was presented. The total resistance in calm water was selected as the objective function, and the overset mesh technique was used for mesh generation. RANS method was used to calculate the total resistance of the hull. In order to improve the efficiency and smoothness of the geometric reconstruction, the arbitrary shape deformation (ASD) technique was introduced to change the shape of the bulbous bow. To improve the global search ability of the particle swarm optimization (PSO) algorithm, an improved particle swarm optimization (IPSO) algorithm was proposed to set up the optimization model. After a series of optimization analyses, the optimal hull form was found. It can be concluded that the simulation based design framework built in this paper is a promising method for bulbous bow optimization. 相似文献
15.
To improve the energy efficiency of ships and to predict ship motion response under actual sea conditions, the far-field theory, strip theory, and Fujii and Takahashi’s modified semi-empirical method are based and studied to calculate the wave-induced added resistance. Firstly, a new modified formula based on the Maruo method is presented to calculate the radiation added resistance for the ship with a complex surface. Meanwhile, some calculation details such as the Green function, the shape of the sections (shape below the still water level or shape below the wave level) in the strip theory, and so on are discussed. Finally, the CFD method is used to simulate the motions of the hull and the added resistance, and the results of the CFD method and those of other numerical methods are analyzed and compared with the experiment results. The modified method in the paper can predict the added resistance in waves for the complex-hull-surface ships well and quickly.
相似文献16.
Resistance and propulsion characteristics of various commercial ships based on CFD results 总被引：2，自引：0，他引：2
This paper uses computational tools to examine the speed performance of various types of commercial ships including resistance and propulsion characteristics. Eight commercial ships built in the last decade were selected for the study. They include four large-sized container carriers, one bulk carrier, one VLCC, and two LNG carriers. The Reynolds averaged Navier-Stokes equation has been utilized, and the computations were executed under the same conditions of the model tests to predict the speed performance, i.e., resistance and self-propulsion. The self-propulsion point was obtained from load-varying tests. The speed performance was predicted based on the model-ship performance analysis method of the revised ITTC’78 method. The limiting streamlines on the hull, wave characteristics around the model ship, and the wake characteristics on the propeller plane were also investigated. After completing the computations, a series of model tests were conducted to evaluate the accuracy of the computational predictions. The predictions clearly reveal the differences in the resistance and propulsion characteristics regarding the various types of commercial ships, and may be applicable to hull-form design. 相似文献
17.
The scale effect of form factor is investigated via a numerical approach in this paper, where the turbulent ship flow is computed by solving the steady and incompressible Reynolds-averaged Navier-Stokes and continuity equations. A wall function approach is employed to bridge the near-wall and outer turbulent flow region. The numerical scheme based on a finite-volume formulation is applied to discretize the coupled governing equation. For the sake of numerical stability, accuracy and economy, an identical grid is employed to compute ship flow at different Reynolds number, where the grid is optimized for the medium Reynolds number of the investigated range. Four surface ships and two sub-bodies with notably different geometrical characteristics are chosen as the investigated cases, where double-model flow without appendages is computed. The calculated total resistance coefficient shows a decreasing tendency against Reynolds number among all studied hulls. Similar to the calculated total resistance coefficient, the calculated friction resistance coefficient decreases with the Reynolds number and varies relatively little for a given Reynolds number among different hulls. The viscous pressure resistance coefficient is less insensitive to the Reynolds number but apparently depends on hull form. Compared with the form factor calculation based on empirical friction lines, the flat-plate friction prediction based on CFD approach clearly gives smaller Re-dependent form factor, which should more realistically reflect the scale effect of form factor. The form factor exhibits a near linear and increasing dependence on Reynolds number. The numerical results show that the dependence of rP on Reynolds number mainly governs the scale effect of form factor. 相似文献
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In this paper, we present a spectral analysis based on wave loads to select suitable side-hull arrangements for a trimaran ship traveling in waves. Neglecting the steady flow effect, the three-dimensional source-distribution method, using a pulsating source potential incorporating the panel method, is adopted to solve the corresponding hydrodynamic coefficients. The significant values for wave loads, including shear forces, bending moments, and torsion moments at different locations on the main hull and connected deck with respect to different staggers and clearances, are derived by the spectral analysis. Several ship speeds and wave headings are also considered for comparison. This study offers more information for selecting the side-hull arrangement from the viewpoint of wave loads on trimaran ships, which may be regarded as helpful references for seakeeping design of these types of ships. 相似文献