共查询到20条相似文献,搜索用时 187 毫秒
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Mooring systems play an important role for semi-submersible rigs that drill in deepwater.A detailed analysis was carried out on the mooring of a semi-submersible rig that conducted a trial well drilling at a deepwater location in the South China Sea in 2009.The rig was 30 years old and had a shallow platform with a designed maximum operating water depth of 457 m.Following the mooring analysis,a mooring design was given that requires upgrading of the rig’s original mooring system.The upgrade included several innovations,such as installing eight larger anchors,i.e.replacing the original anchors and inserting an additional 600 m of steel wires with the existing chains.All this was done to enhance the mooring capability of the rig in order for the rig to be held in position to conduct drilling at a water depth of 476 m.The overall duration of the drilling was 50 days and the upgraded mooring system proved to be efficient in achieving the goal of keeping the rig stationary while it was drilling the trial well in the South China Sea.This successful campaign demonstrates that an older semi-submersible rig can take on drilling in deep water after careful design and proper upgrading and modification to the original mooring system. 相似文献
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Prandtl’s lifting line theory was generalized to the lifting problem of a three-dimensional hydrofoil in the presence of a free surface. Similar to the classical lifting theory, the singularity distribution method was utilized to solve two-dimensional lifting problems for the hydrofoil beneath the free surface at the air-water interface, and a lifting line theory was developed to correct three-dimensional effects of the hydrofoil with a large aspect ratio. Differing from the classical lifting theory, the main focus was on finding the three-dimensional Green function of the free surface induced by the steady motion of a system of horseshoe vortices under the free surface. Finally, numerical examples were given to show the relationship between the lift coefficient and submergence Froude numbers for 2-D and 3-D hydrofoils. If the submergence Froude number is small free surface effect will be significant registered as the increase of lift coefficient. The validity of these approaches was examined in comparison with the results calculated by other methods. 相似文献
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To simulate two-dimensional free-surface flows with complex boundaries directly and accurately, a novel VOF (Volume-of-fluid) method based on unstructured quadrilateral mesh is presented. Without introducing any complicated boundary treatment or artificial diffusion, this method treated curved boundaries directly by utilizing the inherent merit of unstructured mesh in fitting curves. The PLIC (Piecewise Linear Interface Calculation) method was adopted to obtain a second-order accurate linearized reconstruction approximation and the MLER (Modified Lagrangian-Eulerian Re-map) method was introduced to advect fluid volumes on unstructured mesh. Moreover, an analytical relation for the interface’s line constant vs. the volume clipped by the interface was developed so as to improve the method’s efficiency. To validate this method, a comprehensive series of large straining advection tests were performed. Numerical results provide convincing evidences for the method’s high volume conservative accuracy and second-order shape error convergence rate. Also, a dramatic improvement on computational accuracy over its unstructured triangular mesh counterpart is checked. 相似文献
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The water entry problem of an asymmetric wedge with roll motion was analyzed by the method of a modified Logvinovich model (MLM). The MLM is a kind of analytical model based on the Wagner method, which linearizes the free surface condition and body boundary condition. The difference is that the MLM applies a nonlinear Bernoulli equation to obtain pressure distribution, which has been proven to be helpful to enhance the accuracy of hydrodynamic loads. The Wagner condition in this paper was generalized to solve the problem of the water entry of a wedge body with rotational velocity. The comparison of wet width between the MLM and a fully nonlinear numerical approach was given, and they agree well with each other. The effect of angular velocity on the hydrodynamic loads of a wedge body was investigated. 相似文献
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1/4 圆弧面沉箱防波堤设计分项系数研究(英文) 总被引:1,自引:0,他引:1
The quarter-circular caisson breakwater (QCB) is a new type of breakwater, and it can be applied in deepwater. The stability of QCB under wave force action can be enhanced, and the rubble mound engineering can be less than that of semi-circular breakwaters in deepwater. In order to study the wave force distribution acting on the QCB, to find wave force formula for this type of breakwater, firstly in this paper, the distribution characteristics of the horizontal force, the downward vertical force and the uplift force on the breakwater were gotten based on physical model wave flume experiments and on the analysis of the wave pressure experimental data. Based on a series of physical model tests acted by irregular waves, a kind of calculation method, which was modified by Goda formula, was proposed to carry out the wave force on the QCB. Secondly, the reliability method with correlated variables was adopted to analyze the QCB, considering the high correlation between wave forces or moments. Utilizing the observed wave data in engineering field, the reliability index and failure probability of QCB were obtained. Finally, a factor Q=0.9 is given to modify the zero pressure height above SWL of QCB, and wave force partial coefficient 1.34 to the design expressions of QCB for anti-sliding, as well as 1.67 for anti-overturning, were presented. 相似文献
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Research on a multi-grid model for passenger evacuation in ships 总被引:1,自引:0,他引:1
In order to enhance the authenticity and accuracy of passenger evacuation simulation in ships, a new multi-grid model was proposed on the basis of a traditional cellular automata model. In the new model finer lattices were used, interaction of force among pedestrians or between pedestrians and constructions was considered, and static floor fields in a multi-level exit environment were simplified into cabin and exit static floor fields. Compared with the traditional cellular automata model, the multi-grid model enhanced the continuity of the passengers’track and the precision of the boundary qualifications. The functions of the dislocation distribution of passengers as well as partial overlap of tracks due to congestion were realized. Furthermore, taking the typical cabin environment as an example, the two models were used to analyze passenger evacuation under the same conditions. It was found that the laws of passenger evacuation simulated by the two models are similar, while the simulation’s authenticity and accuracy are enhanced by the multi-grid model. 相似文献
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Khac Duc Do 《船舶与海洋工程学报》2011,10(3):325-332
A constructive method was presented to design a global robust and adaptive output feedback controller for dynamic positioning of surface ships under environmental disturbances induced by waves, wind, and ocean currents. The ship’s parameters were not required to be known. An adaptive observer was first designed to estimate the ship’s velocities and parameters. The ship position measurements were also passed through the adaptive observer to reduce high frequency measurement noise from entering the control system. Using these estimate signals, the control was then designed based on Lyapunov’s direct method to force the ship’s position and orientation to globally asymptotically converge to desired values. Simulation results illustrate the effectiveness of the proposed control system. In conclusion, the paper presented a new method to design an effective control system for dynamic positioning of surface ships. 相似文献
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As a kind of clean and renewable energy,tidal current energy is becoming increasingly popular all over the world with the shortage of energy and environmental problems becoming more and more severe.A floating tidal current power station is a typical type of tidal current power transformers which can sustain the loads of wind,waves,and current,and even the extreme situation of a typhoon.Therefore,the mooring system must be reliable enough to keep the station operating normally and to survive in extreme situations.The power station examined in this paper was installed at a depth of 40 m.A 44 mm-diameter R4-RQ4 chain was chosen,with a 2 147 kN minimum break strength and 50 kN pretension.Common studless link chain was used in this paper.Based on the Miner fatigue cumulative damage rule,S-N curves of chains,and MOSES software,a highly reliable mooring system was designed and analyzed.The calculation results show that the mooring system designed is reliable throughout a 10-year period.It can completely meet the design requirements of American Petroleum institution(API).Therefore,the presented research is significant for advancing the design of this kind of power station. 相似文献
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LUShu-ping YANGXue-jing ZHAOXi-ren 《船舶与海洋工程学报》2004,3(1):20-23
As there are lots of non-linear systems in the real engineering, it is very important to do more researches on the modeling and prediction of non-llnear systems. Based on the muhi-resolution analysis (MRA) of wavelet theory, this paper combined the wavelet theory with neural network and established a MRA wavelet network with the scaling function and wavelet function as its neurons. From the analysis in the frequency domain, the results indicated that MRA wavelet network was better than other wavelet networks in the ability of approaching to the signals. An essential research was carried out on modeling and prediction with MRA wavelet network in the non-linear system. Using the lengthwise sway data received from the experiment of ship model, a model of offline prediction was estab lished and was applied to the short-time prediction of ship motion. The simulation results indicated that the forecasting model improved the prediction precision effectively, lengthened the forecasting time and had a better prediction results than that of AR linear model. The research indicates that it is feasible to use the MRA wavelet network in the short -time prediction of ship motion. 相似文献
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为提高设备运行效率,节约人力成本,一些集装箱码头开创了"一拖双挂"技术。介绍集装箱码头牵引车"一拖双挂"技术项目背景和发展情况。分析该项目节能原理,阐述车型选定、实施方案、技术创新点等。该项目取得良好节能效益、经济效益、社会效益。 相似文献
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岸边集装箱起重机自行式驱动小车存在小车易走偏缺陷,直接影响到桥机的装卸效率。用牵引式小车替代自行式小车是个可行的办法。分析了牵引式小车的价值和可行性。从5个重要环节介绍了小车牵引式改造的机械设计。介绍了小车牵引式改造的电气设计。进行了桥机自行式小车牵引式改造的,改造后小车运行平稳,提高了作业效率。 相似文献
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以海上吊物系统为研究对象,考虑长方体吊物模型六自由度的运动和风载荷,建立广义坐标的第二类拉格朗日方程,并利用高阶的龙格-库塔方法求解该方程。根据牛顿第二定律,推导出吊绳动张力计算公式,对不同吊绳长度、不同起吊速度、不同激励频率时的吊绳摆角、吊物转动角度和动张力进行分析。结果表明,吊绳长度,起吊速度和激励频率的变化均对吊物的摆角和吊绳动张力产生很大影响,吊物的升降对吊绳摆动、吊物转动和吊绳中的动张力有抑制作用,且起升速度越大,对吊物系统的抑制效果越明显,可以通过控制起吊速度和时间来减小吊重的摆动。当激励频率接近于吊物系统特征频率时,会出现共振现象,因此起吊作业中需要选择合适的吊索长度以避开共振区。 相似文献