首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到10条相似文献,搜索用时 78 毫秒
1.
In this paper a discussion of three failure criteria during a tanker collision takes place. The ‘Fracture Criterion’ developed recently [Glykas, A., Samouelides, E., Das, P.K. (1996) Energy absorption capacity of plates under lateral loading. Proceedings of the 6th International Conference of Offshore and Polar Engineers, Los Angeles '96, Vol. IV, pp. 502–509.], deals with the amount of energy required so that arbitrary crack propagation originates from microscopic material flaws of the steel structure, in areas of high strain concentration during large deflections. This fracture criterion is applied in critical areas of a tanker bow structure during head-on collision with a vertical rigid body and its validity is examined in comparison to other two state of the art failure criteria. The penetration of the tanker vessel as well as the time to rest from the initiation of the collision are determined in relation to the failure criteria.  相似文献   

2.
The energy dissipation on the bow structure is calculated during a “head-on” collision with a rigid body, using finite element analysis. Gerard's method (Gerard, G., 1958. The crippling strength of compression elements. Journal of the Aeronautical Sciences), an empirical approach, is compared with the results produced by ABAQUS in terms of velocity, energy and penetrating distance. The energy conservation theorem is applied and the contribution of all individual structural members in terms of elastic and plastic energy is calculated. The strain distribution is shown for those members responsible for the water tightness and structural integrity of the structure. The global bending of the upper part of the bow is shown as well as the effect of the total ship mass inertia, phenomena which have not been incorporated into Gerard's approach ( Gerard, 1958). The final time of rest predicted from both methods is compatible and this validates the reliability of the numerical approach.  相似文献   

3.
Emin Korkut   《Ocean Engineering》2006,33(2):205-218
A case study for the energy saving in the powering characteristics of a river going general cargo ship has been carried out. Two different hull forms were generated from the original hull form of the vessel to optimise the stern flow of the vessel. A possible energy saving concept, such as partial wake equalizing duct was investigated in this manner. Resistance, self-propulsion and flow visualization measurements were performed with the hull models to explore the effect of partial wake equalizing ducts on the powering characteristics of the hull form. Analysis of the results indicates that the partial wake equalizing duct concept with an appropriate stern design affect not only the flow characteristics at aft-end, but also the propulsion characteristics. In order to identify effect of each component (partial wake equalizing duct and stern form) a further investigation is needed.  相似文献   

4.
It has been argued that a major shortcoming in the International Maritime Organization (IMO) Interim Guidelines for Approval of Alternative Methods of Design and Construction of Oil Tankers in Collision and Grounding is that grounding and collision damages normalized by the main dimensions of the ship have the same probability density distributions regardless of a particular structural design and ship size.The present paper explores analytical methods for assessing the overall effect of structural design on the damage distributions in accidental grounding and collisions. The results are expressed in simple expressions involving structural dimensions and the building material of the ships. The study shows that the density distribution for collision and grounding damages normalized by the main dimensions of the ship depends on the size of the ship. A larger ship has a higher probability of a larger relative damage length than that of a smaller ship in grounding damage. On the other hand, the damages to the side structure caused by ship collisions are found to be relatively smaller for large ships.The main conclusion is that the existing IMO damage distributions will severely underestimate the grounding damages to the bottom structure of larger vessels and to a lesser extent overestimate collision damages to the side structure of the hull.  相似文献   

5.
Analysis of roll motion and stability of a fishing vessel in head seas   总被引:1,自引:0,他引:1  
The present paper describes an investigation on the relevance of parametric resonance for a typical fishing vessel in head seas. Results for different Froude numbers are discussed based on experimental, numerical and analytical studies.The first region of resonance is investigated. Distinct wave amplitudes are considered. Some intense resonances are found to occur. The paper compares the experimental results with non-linear time simulations of the roll motion. Very good agreement is found, even when large motions take place.Finally, in order to analyze the experimental/numerical results, analytic consideration is given to distinct parameters affecting the dynamic process of roll amplification. The influence of heave, pitch, wave passage effect, speed and roll restoring characteristics are discussed.  相似文献   

6.
The dynamic stability of fishing vessels in longitudinal regular waves is investigated, both analytically and experimentally. In particular, the influence of stern shape on the parametric stability of fishing vessels is studied. Vessels TS and RS have very similar main characteristics, but their sterns are different. Although their linear responses are comparable, both analytical and experimental investigations indicate substantial differences in their dynamic stability in longitudinal regular waves. Strong resonances are found for the vessel with the deep transom. The analytical method takes into consideration the effects of the heave and pitch motions and wave passage and shows good agreement with experimental results. Stability limits are obtained for different conditions and are used as an aid in the discussion of the results obtained in the tests when relevant parameters are changed, such as wave amplitude and frequency, metacentric height and roll damping moment.  相似文献   

7.
Collision and grounding are the most common accidents in ship operation. Some accidents are due to human failure, but several research projects have shown that a high percentage of these accidents could have been avoided if the ship have had better manoeuvrability characteristics. This paper describes how, when the shipyard select some important ship parameters and dimensions at the design stage, these set of parameters influence manoeuvrability characteristics. To obtain these effects, some IMO manoeuvres have been numerically simulated for a sample ship and a non-linear numerical model proposed by the authors to study ship manoeuvrability is described in this work. The day to day practice of a shipyard where fast modelisation and calculations are required, and modifications to the original design are quite common at the preliminary design stage, requires fast but accurate numerical models.  相似文献   

8.
9.
In conjunction with high performance computers, recent developments in computational science paved the path to more accurate representation of body motions inside fluids. Small motions inside the flow can be computationally approximated by using rigid body motion but it is incapable of accurately predicting the large motions of a planing vessel. The implementation of overset grid has made it possible to better approximate the complex fluid-structure interaction problem of the planing regime. The focus of this study was to evaluate the opportunity of using an overset grid system to numerically solve the flow around a planing hull and to understand the planing regime with this invaluable tool. It was shown in this study that the overset grid better captures the large motions of the planing hull at high Froude numbers. Then, the results obtained by overset grid were used to calculate the resistance components of a planing hull in a wide Froude number range. The resistance components were discussed with respect to values generated by Savitsky approach. Using the benefits that the computational science brings, the flow was visualized to explain some underlying physics relevant to the planing regime.  相似文献   

10.
On unstable ship motions resulting from strong non-linear coupling   总被引:1,自引:0,他引:1  
In this paper, the modelling of strong parametric resonance in head seas is investigated. Non-linear equations of ship motions in waves describing the couplings between heave, roll and pitch are contemplated. A third-order mathematical model is introduced, aimed at describing strong parametric excitation associated with cyclic changes of the ship restoring characteristics. A derivative model is employed to describe the coupled restoring actions up to third order. Non-linear coupling coefficients are analytically derived in terms of hull form characteristics.The main theoretical aspects of the new model are discussed. Numerical simulations obtained from the derived third-order non-linear mathematical model are compared to experimental results, corresponding to excessive motions of the model of a transom stern fishing vessel in head seas. It is shown that this enhanced model gives very realistic results and a much better comparison with the experiments than a second-order model.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号