Ship Engineering

Safety Analysis of the Coupled Motions for the Mining Ship Under Extreme Operational Sea Conditions

[Purpose] In order to improve the safety of the mining ship under the action of extreme environmental loads, [Method] based on the three-dimensional potential flow theory, the motion response amplitude operator(RAO) of the mining vessel under various working conditions is calculated. Under the most dangerous wave direction, wind loads and current loads in the same direction are superimposed to form extreme operating conditions. The strength safety of the connection node between the mining vessel and the rigid lifting pipe(the weakest connection part in the system) is selected as the standard for evaluating safety. The motion response data of the mining vessel is imported into the Orcaflex software, and models of the rigid lifting pipe and the relay bin are established to calculate the pipeline force, so as to obtain the force conditions of the connection nodes of the mining system under different loading conditions. [Result] The results show that the dangerous sea conditions can be used as a reference for structural design and a basis for safe operation. When the sea conditions in the operation area reach level 4, the ships under the preparation working conditions need to take certain safety measures. [Conclusion] The research results can provide some references for the design and safe operation of the mining ship.

Remote and Deep-Sea Equipment and Technology

Prediction of Motion and Tension in Mooring System of Floating Wind Turbine Platforms Driven by Environmental Parameters

[Purpose] To meet the demand for short term forecasting of floating wind turbine platform motions and mooring forces while eliminating reliance on real-time motion data, [Method] a deep learning forecasting method driven by environmental parameters is proposed. Training datasets are constructed using random environmental sampling and refined numerical simulations. A dual-branch fully connected network is designed to learn motion and mooring force features separately. The model takes only environmental parameters as input and outputs six-degree-of-freedom motion extremes and mooring force extremes. Z-score normalization, Dropout regularization, and the Adam optimizer are applied to enhance generalization capability. [Result] In the case study of the "Guo Neng Gong Xiang Hao" platform, R² exceeded 0.95 for all motion degrees of freedom except yaw. For mooring force prediction, R² is greater than 0.98 for seven lines, with a maximum mean absolute error of 75.29 k N, accounting for 11% of the pretension, meeting engineering accuracy requirements. [Conclusion] The research results can provide some references for the safety decision-making of floating wind power operation and maintenance.

Construction of Logistics Support System and Development Path in Deep-Sea Aquaculture

[Purpose] With the rapid development of offshore aquaculture vessel and large-scale cage clusters for deepsea aquaculture, the traditional offshore dependent fishery logistics system has been difficult to support longdistance, continuous and high-intensity industrial aquaculture production, and the lack of logistics support capacity has become the key bottleneck restricting the large-scale development of deep-sea aquaculture. To enhance the logistics support capability of deep-sea aquaculture systems, [Method] the prominent problems faced by the deep-sea aquaculture logistics system are analyzed, such as supply interruption, low efficiency of live fish transportation, incomplete cold chain, and insufficient emergency support capabilities. On this basis, a three-level logistics network architecture of "shore based hub-sea node-mobile unit" is proposed, and five subsystems of "material supply, live fish transportation, cold chain logistics, emergency support, and intelligent scheduling" are designed. The equipment system, operation mode, and key technical directions are systematically analyzed. [Result] The results indicate that the logistics support system for deep-sea aquaculture is an important infrastructure to support the operation of industrialized aquaculture systems. The proposed threelevel logistics network architecture and five subsystems can provide systematic ideas for building an efficient and reliable logistics system. [Conclusion] The research results can provide some references for the improvement of the logistics support system for deep-sea aquaculture.

Key Technologies Analysis of Offshore Installation of Mooring System of the First Cylindrical FPSO in the South China Sea

[Purpose] In order to ensure the safe and efficient operation of China's first cylindrical floating production, storage, and offloading(FPSO), "Hai Kui No. 1", applied to the "Liuhua 11-1" oilfieldin the South China Sea under complex sea conditions, [Method] systematic technical research is conducted on the offshore installation of its permanent multi-point polyester mooring system. With dual objectives of risk control and construction efficiency, a comprehensive installation strategy is developed, covering the entire process from suction anchor installation, polyester mooring line laying, restricted reconnection, to tensioning. Key technical challenges are addressed through engineering practice, including heading rotation control of suction anchors, laying techniques for polyester mooring lines with intermediate buoys, improvement of wet-storage stability, and restricted reconnection of the cylindrical FPSO. [Result] The results show that the safe installation and precise tensioning of all 12 polyester mooring lines for "Hai Kui No. 1" are successfully achieved. The maximum displacement the FPSO platform after tensioningis 0.95 m, meeting design requirements and withstanding typhoon conditions. [Conclusion] The research results can provide some references for the engineering practice of deepwater polyester cable mooring systems.

Safe and Efficient Path Planning Methods for USV in Complex Confined Waters

[Purpose] To address the difficulty of reconciling navigational safety with computational efficiency in unmanned surface vehicle (USV) path planning in complex enclosed waters， a safety-oriented path planning method under navigational risk constraints is investigated. [Method] First， a risk-gradient-driven grid map (RG-Map) is constructed， in which the navigational risk gradient is quantified according to the distance to obstacle neighborhoods. Within the jump point search (JPS) framework， a hybrid cost function combining path length and cumulative risk is proposed to provide global guidance; a safety-prioritized pruning strategy and a dynamic weighting mechanism for the heuristic function are further designed to adaptively regulate the search process. A cubic B-spline curve is then applied to smooth the planned path so as to satisfy the kinematic constraints of the USV. [Result] Simulation results in multiple representative enclosed-water scenarios show that， compared with the conventional JPS algorithm， the proposed improved jump point search (IJPS) algorithm reduces the cumulative navigational risk by approximately 45%， yielding a markedly enlarged safety margin. The computational time remains within the same order of magnitude as that of the conventional JPS method， indicating an acceptable efficiency trade-off. The B-spline-smoothed path exhibits continuous curvature and smooth heading transitions. [Conclusion] The proposed method is shown to effectively balance path safety and computational efficiency in complex enclosed waters， enhancing the executability of USV planned paths and offering promising engineering applicability.

Analysis of Collaborative Loading and Structural Response of Semi-Submersible Barge and Immersed Tube During the Entire Installation Process

[Purpose] This study aims to analyze the collaborative loading mechanism between the semi-submersible barge and the immersed tube， and evaluate the structural safety under different working conditions. [Method] Taking the immersed tube construction of the mainline tunnel in the Qianhai Section of the Shenzhen Coastal Expressway as the engineering background， A three-dimensional finite element model was established to investigate the force， deformation， support reactions， and crack control characteristics of the semi-submersible barge and immersed tube under typical conditions of loading onto the barge， floating transport， and immersion. [Result] The results indicate that during the float-up leveling process， the pre-camber adjustment of the elastic support blocks can effectively offset the overall deformation of the immersed tube. The deformation distribution of the semi-submersible barge is symmetrical， the support reactions are uniform， and the maximum tensile stress in the immersed tube is 1.75 MPa， with all crack widths satisfying the code requirements. Under the floating transport condition， the effect of wave loading is limited， with a maximum tensile stress of 1.79 MPa， and all crack widths also satisfying the code requirements. During immersion， the longitudinal deformation of the immersed tube reaches a maximum of 1.2 mm at a depth of 16 m and then decreases， while the transverse deformation reaches 1.9 mm at a depth of 22.3 m. The combined longitudinal and transverse deformation results in a maximum upward camber of 2.3 mm. The crack width at critical sections is ≤0.126 mm， and overall， the structure satisfies the safety requirements. [Conclusion] The study shows that the use of elastic support blocks can significantly optimize the coordinated loading of the semi-submersible barge–immersed tube system and enhance structural safety. This research provides a theoretical basis and technical support for the design of floating transport and immersion construction of immersed tube tunnels in complex marine environments..

A Neural Architecture Search Method for Navigable Water Detection Based on Gradient Optimization

[Purpose] It is crucial for intelligent ships to accurately identify navigable water areas during navigation and berthing in port areas. [Method] This paper proposes a neural architecture search method based on gradient optimization to identify navigable water areas within port areas. Firstly， a neural architecture search (NAS) enhanced U-Net model was proposed based on the U-Net architecture， and the same number of units were used in the encoder and decoder; Secondly， a joint optimization strategy for weight balanced loss was designed， which combines cross entropy and weighted Dice loss to achieve accurate segmentation of navigable water areas; Finally， real ship experiments were conducted and compared with commonly used methods. [Result] Experiments show that the results of this method are superior to U-Net， Vgg-Segnet and Nas-U-Net network models in terms of recall rate， precision rate， F1 value and mean intersection over union. [Conclusion] The experiments showed that the navigable waters segmentation accuracy of proposed method is more accurate and coherent， which meets the needs of navigation and berthing of intelligent ships in port areas.

On Manoeuvrability Prediction for Multipurpose Cargo Ship

In this paper,taking an 27000 DWT multipurpose cargo ship as an example, the calculation has been carried out both for the model and actual ship.Moreover, the comparison between theoretical and experimental results has also been made in the paper.

Present Situation of Welding Production and Development Trend of Welding Technology in China

In this paper, it is verified that the consumption of steel for welded structures in China in 2004 has exceeded 100 million tons, which makes China the world number one welding manufacture country. Since the beginning of the reforming and opening policy in China, many important and large welded structures have been made and welding has played an indispensable role in the development of national economy. The production and application of welding consumables, the distribution of welding robots, the education and training of welding professional are analyzed. Although the yield of welding consumables and welding wires have been expanded rapidly and China has become the largest welding consumables production and consumption country, the rate of manual welding electrodes is still beyond 75%, the welding mechanization and automation rate is around 35% and the ratio between the annual yield of welding consumables and steel is up to 0.77%. These problems should be solved in a shorter time. According to the development trend of welding technology, the applications of welding robot system, fully digital welding power sources, laser and laser hybrid welding, friction stir welding as well as high efficient welding processes should be emphasized in China’s shipbuilding industry. Our international competition strength should be improved by attracting excellent welding professional to the production front and improving the cooperation between governments, enterprises, universities and research institutes as well as with our predominance of high quality, high efficiency and low production costs.

A Review of Approaches to Mechanism of Ship-bridge Collision And Its Nonlinear FEM Simulation

An overview on the mechanism of the ship bridge collision is given in this paper. Employing MSC/DYTRAN program, a normal collision between ship and bridge is simulated. The history of ship bridge collision force, the exchange of energy, the displacements and the stress distribution of the ship bow and various parts of the bridge are presented. Some mechanical rules and characters during the simulated collision are given which are of great value for bridge design, maintenance and damage estimation.

Application study on the Turbulence Models of k-ε Quadratic Equation on CFD Calculation

The paper applies the turbulence models of k-ε quadratic equation to carry on numerical simulation calculation on the circumfluence problem about the slender body,and then the influences of the setting of turbulence parameters in turbulence models on calculation results are compared.The turbulent intensity and the span of viscosity ratio have better flexibility by simulation calculation.By the nonsteady motion calculation on the two-dimensional section,the paper explains the reasonable preferences of turbulence models and verifies the practicability of the turbulence models.

Present Situation of Welding Production and Development Trend of Welding Technology in China

In this paper, it is verified that the consumption of steel for welded structures in China in 2004 has exceeded 100 million tons, which makes China the world number one welding manufacture country. Since the beginning of the reforming and opening policy in China, many important and large welded structures have been made and welding has played an indispensable role in the development of national economy. The production and application of welding consumables, the distribution of welding robots, the education and training of welding professional are analyzed. Although the yield of welding consumables and welding wires have been expanded rapidly and China has become the largest welding consumables production and consumption country, the rate of manual welding electrodes is still beyond 75%, the welding mechanization and automation rate is around 35% and the ratio between the annual yield of welding consumables and steel is up to 0.77%. These problems should be solved in a shorter time. According to the development trend of welding technology, the applications of welding robot system, fully digital welding power sources, laser and laser hybrid welding, friction stir welding as well as high efficient welding processes should be emphasized in China’s shipbuilding industry. Our international competition strength should be improved by attracting excellent welding professional to the production front and improving the cooperation between governments, enterprises, universities and research institutes as well as with our predominance of high quality, high efficiency and low production costs.

Design Study of a Single Point Mooring System in Ultra Shallow Water

On the study of the main form,the type characteristics and the application scope of single point mooring(SPM) system,soft yoke single point mooring system is chosen for the new SPM of "HaiYangShiYou 113" FPSO.The difficulties in the design is studied and the key factors for the design of a SPM in ultra shallow water should be paid more attention,which are design basis,low frequency wave force,bottom striking and green water.The experience is significant for other SPM design in ultra shallow water.