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15 results on '"Baoji Zhang"'

1. Research on the hull form optimization using the surrogate models

Author

Shenglong Zhang, Tahsin Tezdogan, Baoji Zhang, and Ling Lin

Subjects
ship hull form optimization, surrogate model, wave-making resistance, deep belief network, Engineering (General). Civil engineering (General), TA1-2040
Abstract

The ship hull form optimization using the Computational Fluid Dynamics (CFD) method is increasingly employed in the early design of a ship, as an optimal ship hull form can obtain good hydrodynamics. However, it is time-consuming due to its many CFD simulations for the optimization. This paper presents a ship hull form optimization loop using the surrogate model, deep belief network (DBN), to reduce the wave-making resistance of the Wigley ship. The prediction performance of the wave-making resistance of the Wigley ship using the DBN method is discussed and compared with the traditional surrogate models found in this study. The results show that the resistance obtained using the deep belief network algorithm is superior to that obtained using the typical surrogate models. Then, a ship hull form optimization framework is built by integrating the Free From Deformation, non-linear programming by quadratic Lagrangian and deep belief network algorithms. The optimization results show that the deep belief network-based ship hull form optimization loop can be used to optimize the Wigley ship. The study presented in this paper could provide a deep learning algorithm for the ship design optimization.

Published
2021
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2. Research on Ship Hull Optimisation of High-Speed Ship Based on Viscous Flow/Potential Flow Theory

Author

Baoji Zhang

Subjects
potential flow theory, cfd, high speed ship, ship form optimisation, Naval architecture. Shipbuilding. Marine engineering, VM1-989
Abstract

In order to quickly obtain practical ship forms with good resistance performance, based on the linear wave-making resistance theory, the optimal design method of ship forms with minimum total resistance is discussed by using the non-linear programming (NLP) method. Taking the total resistance as the objective function (the Michell integral is used to calculate the wave-making resistance and the equivalent plate friction resistance formula is used to calculate the frictional resistance), the hull surface offset as the design variable and appropriate displacement as the basic constraints, and considering the additional constraints, the hull bow shape and the whole ship are optimised, and an improved hull form is obtained. The resistance of the ship before and after optimisation is calculated by the CFD method to further evaluate the resistance reduction effect and performance after optimisation. Finally, an example of optimisation calculation of an actual high-speed ship is given. The obvious resistance reduction results confirm the reliability of the optimisation design method.

Published
2020
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3. Computational fluid dynamics-based hull form optimization using approximation method

Author

Shenglong Zhang, Baoji Zhang, Tahsin Tezdogan, Leping Xu, and Yuyang Lai

Subjects
Hull forms optimization, approximate method, IPSO-Elman neural network, optimal Latin hypercube design, arbitrary shape deformation, Engineering (General). Civil engineering (General), TA1-2040
Abstract

With the rapid development of the computational technology, computational fluid dynamics (CFD) tools have been widely used to evaluate the ship hydrodynamic performances in the hull forms optimization. However, it is very time consuming since a great number of the CFD simulations need to be performed for one single optimization. It is of great importance to find a high-effective method to replace the calculation of the CFD tools. In this study, a CFD-based hull form optimization loop has been developed by integrating an approximate method to optimize hull form for reducing the total resistance in calm water. In order to improve the optimization accuracy of particle swarm optimization (PSO) algorithm, an improved PSO (IPSO) algorithm is presented where the inertia weight coefficient and search method are designed based on random inertia weight and convergence evaluation, respectively. To improve the prediction accuracy of total resistance, a data prediction method based on IPSO-Elman neural network (NN) is proposed. Herein, IPSO algorithm is used to train the weight coefficients and self-feedback gain coefficient of ElmanNN. In order to build IPSO-ElmanNN model, optimal Latin hypercube design (Opt LHD) is used to design the sampling hull forms, and the total resistance (objective function) of these hull forms are calculated by Reynolds averaged Navier–Stokes (RANS) method. For the purpose of this article, this optimization framework has been employed to optimize two ships, namely, the DTMB5512 and WIGLEY III, and these hull forms are changed by arbitrary shape deformation (ASD) technique. The results show that the optimization framework developed in this study can be used to optimize hull forms with significantly reduced computational effort.

Published
2018
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4. Automatic Optimal Design Method for Minimum Total Resistance Hull Based on Enhanced FFD Method.

Author

Shuhui Guo, Baoji Zhang, Zheng Tian, Jie Liu, and Hailin Tang

Subjects
*PARTICLE swarm optimization, *ALGORITHMS, *SHIPS
Abstract

Hull optimization plays a crucial role in enhancing ship performance and efficiency. This study aimed to improve ship performance, particularly by reducing total resistance, through automated optimization methods. To this end, an integrated, fully automated optimization program was developed based on Python, incorporating Enhanced Free-Form Deformation (FFD) technology, scripted CFD numerical evaluation, and the Particle Swarm Optimization (PSO) algorithm. This program allowed precise control of hull form, improving efficiency while reducing costs. The KCS hull, known for its excellent resistance performance, was chosen as the optimization target, with the goal of minimizing total resistance by adjusting the bulbous bow line plan. The research results indicated that the optimized scheme exhibited lower resistance characteristics compared to the original design while satisfying design constraints. This study not only provides a new optimization strategy for ship design but also lays a foundation for future hull optimization research. [ABSTRACT FROM AUTHOR]

Published
2024
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5. Study on numerical simulation and mitigation of parametric rolling in a container ship under head waves

Author

Liang, Liu, Baoji, Zhang, Hao, Zhang, Jiaye, Gong, Zheng, Tian, Shuhui, Guo, Yuanbiao, Bao, Xu, Zheng, Liang, Liu, Baoji, Zhang, Hao, Zhang, Jiaye, Gong, Zheng, Tian, Shuhui, Guo, Yuanbiao, Bao, and Xu, Zheng

Abstract

To investigate the parametric rolling motion of container ships navigating in head seas, this study utilizes the unsteady RANS approach combined with dynamic overlapping grid technology to simulate parametric roll in a container ship under the coupled motions of roll, pitch, and heave. Initially, the model was validated against experimental results, demonstrating good agreement and thus confirming the reliability of the computational method. Furthermore, the paper investigates the impacts of the initial roll angle, encounter frequency, and the addition of bilge keels on parametric rolling. The research findings indicate that the initial angles of rolling impact the duration needed to attain a steady roll condition, yet they have minimal effect on the amplitude post-stabilization. The likelihood of parametric rolling arises when the frequency of encounters doubles that of the ship’s inherent roll frequency. Furthermore, the likelihood of parametric rolling escalates when the wavelengths approach the length of the ship. Installing bilge keels markedly reduces the parametric rolling movement in vessels, and the occurrence of parametric rolling is also delayed.

Published
2024

6. Study on the effect of marine propeller wake on sediment siltation in a shallow water channel

Author

Liang, Liu, Hao, Zhang, Chaonan, Zhang, Jinbiao, Chen, Baoji, Zhang, Xiangen, Bai, Shengyao, Song, Qian, Chen, Weijia, Zhang, Liang, Liu, Hao, Zhang, Chaonan, Zhang, Jinbiao, Chen, Baoji, Zhang, Xiangen, Bai, Shengyao, Song, Qian, Chen, and Weijia, Zhang

Abstract

In order to investigate the impact of marine propeller wake fields on sediment siltation in shallow water channels, this study employs the unsteady RANS approach and the Volume of Fluid model. A full-scale numerical self-propulsion test was conducted on a 50,000 DWT oil tanker under the influence of a free surface. The research includes forecasting the effect of propeller wakes on sediment redeposition following the dredging of the approach channel to Jiaxing Port in the China Sea. Initially, uncertainty research was carried out on the full-scale ship and propeller system, and the credibility of the computational results was quantified. The simulated results based on the sediment transport numerical model were then compared and validated against actual data from monitoring stations. The self-propulsion performance and the velocity distribution of the propeller wake were examined under three different propeller speeds. Scenarios simulated included no ship navigation, daily single-ship navigation, and daily two-ship navigation, evaluating the siltation distribution within the channel over one month. The results demonstrate that ship propeller wakes positively influence the reduction of channel sedimentation, with the maximum monthly siltation reduction reaching 0.108 m during single-ship tidal navigation and 0.11 m during two-ship tidal navigation.

Published
2024

7. Hydrodynamic performance optimization of marine propellers based on fluid-structure coupling

Author

Liang, Liu, Baoji, Zhang, Hao, Zhang, Hailin, Tang, Weijie, Wang, Liang, Liu, Baoji, Zhang, Hao, Zhang, Hailin, Tang, and Weijie, Wang

Abstract

Fiber-reinforced composites offer the benefits of high strength, high stiffness, lightweight, superior damping performance, and great design capability when compared to metal. The rigidity characteristics of the composite laminate in different directions may be adjusted to meet the requirements of the application by using appropriate materials and arranging the lay-up sequence. As a result, the purpose of this work is to explore the influence of lay-up type on propeller performance in terms of both hydrodynamic and structural performance. A transient fluid-structure interaction (FSI) algorithm based on the finite element method (FEM) combined with the computational fluid dynamics (CFD) technique is developed and used for the analysis of composite propellers. The hydrodynamic performance of the propeller is compared to that of a metallic material. Propeller propulsion efficiency, structural deformation, equivalent stress, and damage performance of different lay-up options under three different operating situations are compared. In addition, it is presented a parametric optimization approach to get the most appropriate lay-up program for composite blades with the best hydrodynamic properties and structural performance.

Published
2023

9. Hydrodynamic Performance of Open-frame Deep Sea Remotely Operated Vehicles Based on Computational Fluid Dynamics Method

Author

Qianrong Li and Baoji Zhang

Abstract

The resistance performance and motion stability of deep sea remotely operated vehicles (ROVs) subjected to underwater motion conditions are studied on the basis of the unsteady Reynolds-averaged Navier-Stokes method combined with the six-degree-of-freedom equation of motion to quickly and accurately predict them. In the modeling process, we consider the complexity of ROV geometry and thus reduce the model to a series of regular geometries to maximize the position and weight of the original components. The grid and value slots of an ROV are divided, and the surface is reconstructed. The forward, backward, transverse, floating, and submerged resistance of ROVs are simulated and compared with existing experimental forces to determine the accuracy of the calculation method. Then, the oblique navigation of the ROV on the horizontal and vertical planes is studied. Furthermore, the motion response of the ROV to direct horizontal motion, heave, pitch, and yaw are studied. The force, moment, and motion time curves are obtained. The stability of ROV motion is analyzed to provide technical support for the safety of ROVs.

Published
2022
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10. Study on the Analysis Method of Ship Surf-Riding/Broaching Based on Maneuvering Equations

Author

Baoji Zhang and Lupeng Fu

Abstract

In order to understand the mechanism of the surf-riding/broaching profoundly, the four- degree- of-freedom(4DOF) maneuvering equation (surge, sway, yaw and roll) is simplified to a one- degree-of-freedom (1DOF) equation, and the fourth-order Runge-Kutta method is used to integrate a 1DOF surge equation in the time domain to analyze the two motion states of the ship during the surging and surf-riding. The critical Froude number is calculated using the Melnikov method. Taking a fishing boat as an example, the ship’s surf-riding/broaching phenomenon is simulated under the condition of wavelength-to-ship-length ratio and wave steepness, 1 and 1/10 respectively, providing technical support for the formulation of the second generation intact stability criteria.

Published
2022
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11. Analysis of the Effect of Supplying Vessel on Wave Drift Force of Semi-Submersible Platform

Author

Chi Zhang and Baoji Zhang

Subjects
Software, business.industry, Mooring system, Potential flow, Mathematics::Differential Geometry, Direction angle, Interference (wave propagation), Mooring, business, Geology, Marine engineering
Abstract

Wave drift force is the key factor affecting the mooring ability of semi-submersible platform. Aiming at the mooring system composed of replenishment ship and semi-submersible platform, the influence of hydrodynamic interference on semi-submersible platform is analyzed. Based on the three-dimensional potential flow theory and AQWA software, the effects of different wave directions and spacing on the wave drift force of semi-submersible platform are considered. The results show that the hydrodynamic interference of the replenishment ship will affect the wave drift force of the semi-submersible platform, and the influence of the distance between adjacent vessels and the wave direction angle is more sensitive in the middle and high wave frequencies. This paper can provide support for the research of hydrodynamic interference of semi-submersible platform.

Published
2019
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12. Numerical Simulation of Resistance Field of Hull-Propeller-Rudder Coupling

Author

Baoji Zhang and Hong Xie

Subjects
Body force, Computer simulation, law, Hull, Propeller, Compressibility, Rudder, Hydrostatic equilibrium, Reynolds-averaged Navier–Stokes equations, Marine engineering, Mathematics, law.invention
Abstract

Based on the incompressible RANS equation, the KVLCC1 ship's resistance field's numerical simulation is carried out. In this paper, the bare hull (calm water resistance and wave resistance) and hull-propeller-rudder models are studied and compared with the values of the Hydrostatic resistance test. In the hull-propeller-rudder system's performance analysis, the body force method is used to replace the real propeller model. The new calculation domain is set for the hull-propeller-rudder system model and meshed again to obtain the highly reliable numerical simulation results. Finally, the calculation results are analyzed. The research results in this paper can provide technical support for the resistance of similar ship types.

Published
2021
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13. Study on Mooring Design and Calculation Method of Ocean Farm Based on Time-Domain Potential Flow Theory

Author

Yuhang Sun and Baoji Zhang

Subjects
Computer science, Catenary, Anchoring, Point location, Potential flow, Sensitivity (control systems), Time domain, Mooring, Wind speed, Marine engineering
Abstract

In order to calculate the mooring force of a new semi-submerged Ocean Farm quickly and accurately, based on the unsteady time-domain potential flow theory and combined the catenary model, the control equation of mooring cable is established, and the mooring force of the platform under the wave spectrum is calculated. First of all, based on the actual situation of the ocean environment and platform, the mooring design of the platform is carried out, and the failure analysis and sensitivity analysis of the single anchor chain by the time domain coupling method are adopted: including different water depth, cycle, pretension size, anchor chain layout direction and wind speed, etc. The analysis results confirm the reliability of anchoring method. Based on this, the mooring point location of the platform is determined, the force of each anchor chain in the anchoring process is calculated, and the mooring force and the number of mooring cables are obtained for each cable that satisfies the specification, the results of this paper can provide theoretical calculation methods for mooring setting and mooring force calculation of similar offshore platforms.

Published
2020
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14. Semi-submersible Offshore Coupled Motion in Irregular Waves

Author

Baoji Zhang and Ying Wang

Subjects
Discretization, Turbulence, business.industry, Free surface, Wave height, Finite difference method, Volume of fluid method, Probability density function, Mechanics, Computational fluid dynamics, business, Geology
Abstract

In order to predict the hydrodynamic performance of semi-submersible offshore platform accurately, based on CFD theory, continuous equation and N-S equation as the control equation, RNG type k-ε model as turbulence model, using the finite difference method to discretize the control equation，using the Semi-Implicit Method for Pressure Linked Equation (SIMPLE) algorithm to solve the control equation，using the VOF method to capture the free surface. The numerical wave tank of irregular wave is established, and the wave force and motion response of the semi-submersible platform under irregular wave are studied. Based on the Jonswap spectrum density function, for a certain area of two irregular waves (South China sea, a-ten-year return period, a-hundred-year return period) sea condition, five wave direction Angle (0 °, 30 °, 45 °, 60 °, 90 °), a total of 10 kinds of conditions of the motion response of semi-submersible platform are simulated, through analysis and comparison of simulation results, the influence law of wave angle, wave period and wave height on platform motion is obtained. Compared with the experimental values, the results of heave and pitch are close to the experimental data under the sea condition of 2, 0 degree wave angles. The research results in this paper can provide reference for the design and motion response prediction of practical semi-submersible offshore platforms.

Published
2020
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15. DirectN-Arylation of Azaheterocycles with Aryl Halides under Ligand-free Condition

Author

Mingjie Zhang, Qichao Yang, Baoji Zhang, and Yufang Wang

Subjects
chemistry.chemical_classification, chemistry.chemical_compound, Base (chemistry), chemistry, Ligand, Aryl, Aryl halide, Organic chemistry, Halide, General Chemistry, Combinatorial chemistry, Catalysis
Abstract

A simple and efficient CN cross-coupling method of aryl halides with various heterocycles was reported, by using 10 mol% of CuI as catalyst and 1.2 equiv. NaH as base. Aryl iodides, aryl bromides and many substituted aryl chlorides could efficiently react with heterocycles, providing variety of N-arylated products in good to excellent yields. The ligand-free catalyst system was stable in air and could be readily reused.

Published
2012
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