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ZONG Zhi DONG Guo-hai 《船舶与海洋工程学报》2007,6(2):1-5
Among all environmental forces acting on ocean structures and marine vessels, those resulting from wave impacts are likely to yield the highest loads. Being highly nonlinear, transient and complex, a theoretical analysis of their impact would be impossible without numerical simulations. In this paper, a pressure-split two-stage numerical algorithm is proposed based on Volume Of Fluid (VOF) methodology. The algorithm is characterized by introduction of two pressures at each half and full cycle time step, and thus it is a second-order accurate algorithm in time. A simplified second-order Godunov-type solver is used for the continuity equations. The method is applied to simulation of breaking waves in a 2-D water tank, and a qualitative comparison with experimental photo observations is made. Quite consistent results are observed between simulations and experiments. Commercially available software and Boundary Integral Method (BIM) have also been used to simulate the same problem. The results from present code and BIM are in good agreement with respect to breaking location and timing, while the results obtained from the commercial software which is only first-order accurate in time has clearly showed a temporal and spatial lag, verifying the need to use a higher order numerical scheme. 相似文献
13.
Hiroshi Isshiki 《Journal of Marine Science and Technology》2001,6(2):93-109
To discuss water-wave problems in unlimited waters, it is important to know what type of wave radiation condition should
be placed on a virtual surface corresponding to infinity. For this kind of problem, the Sommerfeld radiation condition is
well known. In this article, the condition is extended to treat a case with an incident wave. Furthermore, a more general
wave radiation condition is introduced from a different point of view. The above-mentioned wave radiation conditions are introduced
into the variational principles of the Kelvin, Hellinnger–Reissner, and Dirichlet type. The Dirichlet-type variational principles
are then used in numerical calculations for bending waves in a bar, and the effectiveness of the wave radiation conditions
and the variational principles is shown. The numerical results for one-dimensional water-wave problems are then given. As
expected, the region required for the numerical solution is reduced drastically compared with that required by the Sommerfeld-type
formulation. Furthermore, the amplitude of the diverging wave is obtained in the process of reaching the variational solution.
Finally, two-dimensional water-wave problems are briefly discussed.
Received: August 9, 2001 / Accepted: September 17, 2001 相似文献
14.
The Powell's method was developed to determine the optimal stiffness and damping of multi-tuned mass dampers (MTMD) in offshore wind turbine (OWT) support structures under fatigue loads. Numerical examples indicated that the Powell's method results are always better than those using MTMD formulations. With the exception of the blade passing (3P) frequency, it was found in this work that a positive integer (n) multiple of the 3P frequency will also result in a large wind-induced vibration, which can be excited by the frequency of the first structural vertical rotation mode and will cause significant fatigue damage. The first translation mode TMD installed at the tower top is efficient to increase fatigue life at the tower and brace connections, but it cannot reduce fatigue damage at the column and brace connections below the platform. The second translation mode TMD can reduce fatigue damage resulting from large wave loads and thus increase the fatigue life of the braces and columns. The mode-3 TMD with a reduction in the 3(3P) vertical rotation can effectively increase the fatigue life of the braces and columns. Thus, the appropriate use of these TMDs can be effective for the fatigue problem of OWT support structures. 相似文献
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本文简要阐述了影响船舶总纵强度的主要因素,并对《钢质内河船舶建造规范》(2009)中将船舯剖面处的最小剖面模数表示成型深D的表达形式提出了自己的见解,并指出了总纵弯矩与中剖面最小剖面模数计算公式中的不协调。 相似文献
19.
李勋文 《筑路机械与施工机械化》2007,24(3):44-45,55
在混凝土泵车臂架修复的意义和类型的基础上,针对一台大修的混凝土泵车臂架断裂的具体部位和外貌特征,经过拆分、检查、测量、连杆机构分析、出图、调试等修理过程,找出臂架开裂的原因,进行修复,并对原有结构中可能再次损坏的薄弱部位进行预加强,以达到与其他结构等寿命的目的。 相似文献
20.
Roberto?MuscariEmail author Andrea Di?Mascio 《Journal of Marine Science and Technology》2003,8(2):61-67
A numerical model for the simulation of two dimensional spilling breaking waves is described. It is derived from a previous model which, in turn, takes its underlying ideas from the Cointe and Tulin theory of steady breakers. With respect to the former model, the present one is local, i.e., the inception, extension, and geometry of the breakers are determined through the local shape of the water surface. The model has been implemented in a RANSE code, which was developed for the simulation of ship flows, through a modification in the boundary conditions. This yields a simple and effective way to reproduce the breakers influence on the underlying flow. The resulting code has been used to simulate the flow past a submerged hydrofoil. The numerical results are compared with those of the previous model and with the experimental data obtained by Duncan. 相似文献