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A CFD method was proposed to numerically simulate zigzag test in three dimensional numerical tank. By solving the RANS equations and the ship motion equations, as well as the singlephase Level Set method, the simulation of zigzag test was carried out in the unsteady viscous flow field around the ship. Meanwhile, the change of navigation attitude was realized by using the overlapping grid technique. The ship of “YUKUN” was taken as an example for the 10°/10°zigzag test simulation. It is shown that the numerical results have a good agreement with experimental data.
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By analyzing the defect existing in the present navigation simulator, a new idea was put forward, as result, a new intelligent navigation simulator was achieved by integration of the PIDVCA method, that is the realization of the intelligent own ship and target ship. The target ships in the new designed intelligent navigational simulator was provided with the ability of giving way to other ships, and the intelligent own ships can offer the collision avoidance scheme for the trainees under the complicated encountering situation to simulate the real action of the targets at sea. By large amounts of simulation instances, the PIDVCA method integrating into the navigation is practicable and can highly improve the quantity of the simulator.
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Aiming at the characteristic of many equipments and complex functions for some ship power systems, the mathematic model of major power equipments was established by using modularity modeling method. Based on the system simulation models, the real-time simulation for the ship power system was realized under various operation conditions. Results show that simulation data of the models are in good agreement with actual operation ones, the models can reflect the actual operating conditions of the power plant and meet the requirement of simulation.
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To build simulation platform of single-boat mid-water trawl system, the single-boat mid-water trawl hydrodynamic model was established by adding motion model of fishing boat, mathematical model of trawler, and fishing net on navigation simulator, and the 3D visualization of fishing module was also developed by the 3D graphics engine OSG(OpenSceneGraph). The simulation platform included instructor station, GMDSS communication, ECDIS, Radar/ARPA, integrated information display and fishing module unit.Testing results show that the visual and real-time effects satisfy the requirements of visual system in navigation simulator with a good stability.
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为获得LNG船舶更准确的风压分布和更多的风场细节，只对LNG船舶的货舱风阻进行数值分析，忽略船体以及其他上层建筑部分.选用RNG k-ε湍流模型和大涡模拟方法对均匀风场中的LNG船舶球形货舱绕流进行数值模拟.为验证数值方法和网格划分的合理性，对均匀风场中的半球体绕流进行数值模拟，计算结果与风洞试验的数据吻合很好.对LNG船舶球形货舱的绕流场和风压分布分析发现，大涡模拟方法对漩涡流动的模拟有较好的效果.
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Aiming at the features of ship lights recognition model under complex light environment such as strong nonlinearity, high dimension and complex environmental disturbances, a ship lights recognition model based on BP neural network was proposed. The relevant factors were selected as network inputs, and the identification code was set as network output to make up BP neural network model. Immune clonal selection optimization algorithm was adopted to decide the network layers and the number of units in each layer, by combining with sensitivity analysis method to search the direction and scale of nonlinear optimization to reduce the number of iterations the BP neural network and improve the search efficiency.Based on the spot photoes of ship lights, simulations of ship lights recognition were conducted by using the improved neural recognition model. Simulation results demonstrate the efficiency of the proposed ship lights recognition model.
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A series of model tests were carried out to study the process of oil leakage from the damaged oil tanker with the rupture on the side and underwater, which has the same size but different height. And some essential data were analyzed in different cases, such as the duration, the velocity and the volume of leakage. Result shows that the overall process is composed of two different stages. The difference of pressure and density between the water and oil is the driven force in these two stages. While the effect of rupture hole height plays an important role in the overall process,not only the duration of different stage but also the volume of oil leakage from the oil tank. Finally, the dynamic mechanism and characters are illustrated by studying the effect of rupturehole height on the oil leakage process in different stages by using the model test.
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The status of ship maintenance and repair management was analyzed from aspects of maintenance system, mathematical methods and models, and development of decision support system, etc. Result shows that there has a larger development space in ship maintenance management method research, and the research of new optimization model and algorithm and their applications, the development and application of maintenance decision support system are still the focuses and directions in the future research. Marine repair at sea should also be on the agenda.
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To investigate the structural characteristics and evolution mechanism of shipping network, the weighted Asia shipping network was constructed. The topological and weighted structure were analyzed based on relative index, and BBV model was used to simulate the evolution of shipping network. It is shown that in the topological network the average path length is smaller, and the clustering coefficient is larger, the node degree appear normal distribution. Therefore, the topological structure is a small-world network. For the weighted network, the clustering coefficient and average path length are smaller, the node strength and edge weight appear respectively power-law and long-tail distribution, therefore, classified as scale-free network. Furthermore, the simulation network based on BBV is similar to the shipping network, thus BBV model can simulate the evolution of shipping network.
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The location of water emergency supplies repertories and the allocation of emergency supplies were integrated. Based on the set covering theory and gravity model, an optimization location-allocation model was established, and then a genetic algorithm was designed. The numerical example results show that the location-allocation results can achieve universal coverage of the water area and backup coverage of the key water area. The fact of 43 times same result by 50 times running program states clearly the stability of calculation.The numerical example results indicate the feasibility of location-allocation model and algorithm.
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In order to scientifically evaluate and optimize the container transport organization mode of upper Yangtze river, the typical segment of Yangtze river container transport organization mode was simulated by Flexsim simulation software. Combining with the exports of upper Yangtze container, the upper Yangtze container transport organization model was established. The Flexsim simulation tester was used, and the total transportation cost and the ratio of the ship were optimized by setting the experimental parameters and evaluations. The results of transport organization system coincides with that of the actual situation. Transit mode has a comparative advantage on aspects of vessel cost, voyage loading rate and waiting time in port, but the differences between the two modes on total cost and average loading rate are very small.
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In order to explore the mechanism of unsteady flow in a highly loaded compressor cascade with large positive incidence,the separation vortices evolution and the effect of the vortices on flow field parameters were analyzed and discussed with the topological analysis and numerical simulation method.Results show that there are two kinds of vortices in cascade passage at incidence of +15°,suction surface separation vortex and trailing edge shedding vortex.The vortex-shedding frequency of suction surface separation vortex is 104.7 Hz.The double frequency 211.5 Hz is caused by the alternative shedding of trailing edge shedding vortex and suction surface separation vortex.During the development process of the separation vortex,it may restrain and merge puny vortices.Meanwhile the separation vortex makes the aerodynamic loading of blade rise obviously.
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Full-annulus unsteady simulations were carried out to obtain the internal flow field structure in an axial flow compressor at design point and near stall point, especially the internal flow of compressor at stall point was studied. Results show that, at near stall point, shock waves in rotor passages move forward, and form stronger shock waves by combining with the detached shock waves. The shock waves at 20% span of rotor move forward most seriously, leading to a heavy boundary separation on the rotor suction side. Influenced by rotor wake flow, large scale separation zones generated at stator corner and space ring vortex formed.
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Aiming at the problem of maneuvering target tracking under nonlinear observation, an S-amended unscented Kalman filtering (SUKF) was developed by using the idea of S-amended anti-divergent method for Kalman filter in linear filtering and improving the performance of unscented Kalman filtering algorithm. Two-dimensional maneuvering target tracking simulations were carried out, and results show that tracking accuracy is significantly improved comparing with the basic UKF algorithm, but calculation time increases slightly. Comparing with the basic UKF algorithm, tracking accuracy is improved, and calculation time reduces signif
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A comprehensive energy-saving sail (CES) was designed in order to promote energy saving and emission reduction of shipping. The CES can utilize wind for propulsion and power generation at the same time with its unique structure to collect wind energy. The feasibility of computational fluid dynamic (CFD) numerical model was verified by a case on arc wind sail, then this model was used to simulate the pressure field and velocity field around the sail. Results show that the outlet velocity of air tube vo and wind field velocity vi can be expressed as an equation vo≈1.31vi, therefore CES can effectively improve the conversion efficiency, and utilize wind for propulsion and turbine. The energy saving and emission reduction of Japanese coal cargo ship installed with CES were calculated based on the equation, the effect of energy saving and emission reduction on the voyage were verified.
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The analysis of characteristics of marine radar target echo signals, including the area, correlation of the shape complexity and the amplitude of the target echo signal, was conducted by using the recorded radar video signal. Results show that the characteristic parameters of the same target appears strong correlation and stability. Thus these characteristic parameters can be employed to the target detection and tracking algorithms to improve the performances. It can also be used in radar target simulation to make the simulated radar target echo signals looks more close to the real ones.
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The direct torque control method based on voltage vector was selected to control the torque ripple. The voltage vector controller adopts bang-bang hysteresis control. The observer of flux linkage can be estimated online and to be improved at the same time through enhancing the measurement accuracy of voltage and current. As for torque observer, the instantaneous torque can be got through intelligent identification method by adaptive neural network. Simulation and experiment results show that the direct torque control method not only can ensure SRM reliable operation and the constant torque, but also can restrain torque ripple effectively to some degree.
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Remote sensing techniques are very advantageous and potential allowing for the overcoming of the spatial limitations of fixed point observations on sea. These techniques allow for implementation of large-range and multi-temporal monitoring during the construction of large ocean engineering.The practice indicated that a retrieval model, built by the spectrum of visible red band-3 (0.63~0.69 μm) of Chinese Huanjing (HJ-1A/1B) images, had high accuracy and objectively reflected the distribution and variation of suspended particulate matter (SPM) during large-scale reclamation.The reclamation of Dalian offshore airport was considered as a case study. The comprehensive analysis of numerical simulations, fixed point observations and remote sensing techniques, succeed in monitoring the anytime SPM during the construction of the ocean engineering in a large-scale at area.
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The fatigue analysis and life evaluation of Changshan cable stayed bridge under vehicle loads were completed according to the S-N curve and linear cumulative damage rule. The influence line of displacement of fixed pier-pylon-beam was drawn by using ANSYS to find out the most disadvantageous load position, and the fatigue life of fixed pier-pylon-beam was calculated by combining the result with the fatigue analysis software FE-SAFE. Results show that fixed pier-pylon-beam of Changshan bridge is prone to fatigue failure, the fatigue life of internal rope zone of the bridge is lower than the edge cable, which provides a reference for future maintenance of Changsha bridge.
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Taking the below-river-passing tunnel construction of a section (from Xueyuan Square to Dalian Maritime University) of Dalian metro line 1 as subject, a back analysis method and realizing process of differential evolution was established with the index of displacement value, through carrying on the back analysis of the tunnel surrounding rock mechanics parameters based on a latest superior algorithm—differential evolution. The mentioned surrounding rock mechanics parameters were used to schemes comparison and stabilization analysis of the below-river-passing tunnel excavation construction to verify its viability and availability under complicated geological conditions. It is shown that this method does have its viability and reference effects for construction schemes selection and tunnel security.Besides, the mentioned surrounding rock mechanics parameters deserve the further application to the related research of certain similar constructions.
