A real free surface boundary condition,taking the viscous effects and surface tension into account,is applied to the nonlinear calculation of wave making resistance.It may provide more information about the character ...A real free surface boundary condition,taking the viscous effects and surface tension into account,is applied to the nonlinear calculation of wave making resistance.It may provide more information about the character of the nonlinear ship wave and be helpful to improving the stability,convergence and local wave profile in potential calculation of the nonlinear ship wave.The wave making calculations for Series 60 are presented.展开更多
The roles of shipping culture were introduced firstly,and then the development situation of Shanghai Free Trade Zone was analyzed. Finally,the ration between shipping culture and the construction of Shanghai Free Trad...The roles of shipping culture were introduced firstly,and then the development situation of Shanghai Free Trade Zone was analyzed. Finally,the ration between shipping culture and the construction of Shanghai Free Trade Zone was discussed to provide reference for the development of Shanghai Free Trade Zone.展开更多
We consider the problem of a ship advancing in waves. In this method, the zone of free surface in the vicinity of body is discretized. On the discretized surface, the first-order and second-order derivatives of ship w...We consider the problem of a ship advancing in waves. In this method, the zone of free surface in the vicinity of body is discretized. On the discretized surface, the first-order and second-order derivatives of ship waves are represented by the B-Spline formulae. Different ship waves are approximated by cubic B-spline and the first and second order derivates of incident waves are calculated and compared with analytical value. It approves that this numerical method has sufficient accuracy and can be also applied to approximate the velocity potential on the free surface.展开更多
Adopting complex number theory, a mathematic model of Green function is built for two dimension free water surface, and an analytic expression of Green function is obtained by introducing two parameters. The intrinsic...Adopting complex number theory, a mathematic model of Green function is built for two dimension free water surface, and an analytic expression of Green function is obtained by introducing two parameters. The intrinsic properties of Green function are discussed on vertical line and horizontal line. At last, the derivation expression of Green function is obtained from the formula of Green function.展开更多
The hydroelastic analysis and sonoelastic analysis methods are incorporated with the Green＇s function of the Pekeris ocean hydro-acoustic waveguide model to produce a three-dimensional sonoelastic analysis method for...The hydroelastic analysis and sonoelastic analysis methods are incorporated with the Green＇s function of the Pekeris ocean hydro-acoustic waveguide model to produce a three-dimensional sonoelastic analysis method for ships in the ocean hydro-acoustic environment. The seabed condition is represented by a penetrable boundary of prescribed density and sound speed. This method is employed in this paper to predict the vibration and acoustic radiation of a 1 500 t Small Water Area Twin Hull （SWATH） ship in shallow sea acoustic environment. The wet resonant frequencies and radiation sound source levels are predicted and compared with the measured results of the ship in trial.展开更多
In this paper a submerged horseshoe vortex under a free surface is discussed and the algebraic expression of the wave elevation is obtained. From this expression, some characteristics of the ship wave are described. T...In this paper a submerged horseshoe vortex under a free surface is discussed and the algebraic expression of the wave elevation is obtained. From this expression, some characteristics of the ship wave are described. There exists a smooth region nearθ=0°, but when the uniform stream passes the other singularities （source, sink, doublet, etc.） there is no smooth region. The mechanism of synthetic aperture radar （SAR） images of the narrow ship wakes is also explained.展开更多
Reducing the fuel consumption of ships presents both economic and environmental gains. Although in the past decades,extensive studies were carried out on the flow around ship hull, it is still difficult to calculate t...Reducing the fuel consumption of ships presents both economic and environmental gains. Although in the past decades,extensive studies were carried out on the flow around ship hull, it is still difficult to calculate the flow around the hull while considering propeller interaction. In this paper, the viscous flow around modern ship hulls is computed considering propeller action. In this analysis, the numerical investigation of flow around the ship is combined with propeller theory to simulate the hull-propeller interaction. Various longitudinal positions of the rudder are also analyzed to determine the effect of rudder position on propeller efficiency. First, a numerical study was performed around a bare hull using Shipflow computational fluid dynamics(CFD) code to determine free-surface wave elevation and resistance components.A zonal approach was applied to successively incorporate Bpotential flow solver^ in the region outside the boundary layer and wake, Bboundary layer solver^ in the thin boundary layer region near the ship hull, and BNavier-Stokes solver^in the wake region. Propeller open water characteristics were determined using an open-source MATLAB code Open Prop, which is based on the lifting line theory, for the moderately loaded propeller. The obtained open water test results were specified in the flow module of Shipflow for self-propulsion tests. The velocity field behind the ship was recalculated into an effective wake and given to the propeller code that calculates the propeller load. Once the load was known, it was transferred to the Reynolds-averaged Navier-Stokes(RANS) solver to simulate the propeller action. The interaction between the hull and propeller with different rudder positions was then predicted to improve the propulsive efficiency.展开更多
锚框结构的舰船目标检测算法存在预设锚框与真实目标框难以精准匹配的问题,设计了一种基于合成孔径雷达(Synthetic Aperture Radar,SAR)图像的无锚框实时舰船目标检测算法。该算法以YOLOX-Nano(You Only Look Once X-Nano)框架为基础,...锚框结构的舰船目标检测算法存在预设锚框与真实目标框难以精准匹配的问题,设计了一种基于合成孔径雷达(Synthetic Aperture Radar,SAR)图像的无锚框实时舰船目标检测算法。该算法以YOLOX-Nano(You Only Look Once X-Nano)框架为基础,在骨干网络单元嵌入改进Ghost模块和挤压激励(Squeeze and Excitation,SE)模块。路径聚合网络(Path Aggregation Network,PANet)与改进Ghost模块和自适应空间特征融合(Adaptively Spatial Feature Fusion,ASFF)模块集成后提高了模型的特征表达能力。以输入图像分辨率为320×320像素为基准,相较于单发多框检测器(Single Shot MultiBox Detector,SSD)和YOLOv3-tiny(You Only Look Once v3-tiny)模型,实验结果显示本文算法在合成孔径雷达舰船检测数据集(SAR Ship Detection Dataset,SSDD)上平均正确率达到94.5%,参数量为0.87×10^(6),浮点计算量为0.61×10^(9),能够实现高精度和低复杂度的SAR图像舰船目标检测。展开更多
在对系统功能进行总体分析的基础上,采用SQL Server 2005建立了系统所需的船型数据库。使用ASP.NET技术和集成开发工具Microsoft Visual Studio 2008,选用C#为编程语言,调用船舶设计软件Free!ship开发了基于Web的船型变换系统。研究结...在对系统功能进行总体分析的基础上,采用SQL Server 2005建立了系统所需的船型数据库。使用ASP.NET技术和集成开发工具Microsoft Visual Studio 2008,选用C#为编程语言,调用船舶设计软件Free!ship开发了基于Web的船型变换系统。研究结果表明,该系统可以方便快捷地生成船体型线,加速船舶设计进程,实现船型数据共享。展开更多
文摘A real free surface boundary condition,taking the viscous effects and surface tension into account,is applied to the nonlinear calculation of wave making resistance.It may provide more information about the character of the nonlinear ship wave and be helpful to improving the stability,convergence and local wave profile in potential calculation of the nonlinear ship wave.The wave making calculations for Series 60 are presented.
基金Supported by Educational Science Research Project of Shanghai City(C16064)Key Teaching Reform Project for Undergraduate Education of Colleges and Universities in Shanghai City"Research and Practice of Training Modes of Shipping Professionals Based on Collaboration among Different Domains from a Perspective of Innovation and Entrepreneurship Education"
文摘The roles of shipping culture were introduced firstly,and then the development situation of Shanghai Free Trade Zone was analyzed. Finally,the ration between shipping culture and the construction of Shanghai Free Trade Zone was discussed to provide reference for the development of Shanghai Free Trade Zone.
文摘We consider the problem of a ship advancing in waves. In this method, the zone of free surface in the vicinity of body is discretized. On the discretized surface, the first-order and second-order derivatives of ship waves are represented by the B-Spline formulae. Different ship waves are approximated by cubic B-spline and the first and second order derivates of incident waves are calculated and compared with analytical value. It approves that this numerical method has sufficient accuracy and can be also applied to approximate the velocity potential on the free surface.
文摘Adopting complex number theory, a mathematic model of Green function is built for two dimension free water surface, and an analytic expression of Green function is obtained by introducing two parameters. The intrinsic properties of Green function are discussed on vertical line and horizontal line. At last, the derivation expression of Green function is obtained from the formula of Green function.
文摘The hydroelastic analysis and sonoelastic analysis methods are incorporated with the Green＇s function of the Pekeris ocean hydro-acoustic waveguide model to produce a three-dimensional sonoelastic analysis method for ships in the ocean hydro-acoustic environment. The seabed condition is represented by a penetrable boundary of prescribed density and sound speed. This method is employed in this paper to predict the vibration and acoustic radiation of a 1 500 t Small Water Area Twin Hull （SWATH） ship in shallow sea acoustic environment. The wet resonant frequencies and radiation sound source levels are predicted and compared with the measured results of the ship in trial.
基金Project supported by the National Natural Science Foundation of China （Grant No 10372025） and the National Key Basic Research Special Foundation of China （Grant No 2001CB309400）.
文摘In this paper a submerged horseshoe vortex under a free surface is discussed and the algebraic expression of the wave elevation is obtained. From this expression, some characteristics of the ship wave are described. There exists a smooth region nearθ=0°, but when the uniform stream passes the other singularities （source, sink, doublet, etc.） there is no smooth region. The mechanism of synthetic aperture radar （SAR） images of the narrow ship wakes is also explained.
基金the Committee for Advanced Studies and Research(CASR)Bangladesh University of Engineering and Technology for granting research fundsub-project CP No.2084 of Department of Naval Architecture and Marine Engineering under Higher Education Quality Enhancement Project(HEQEP),UGC,Ministry of Education,Govt.of Bangladesh for providing necessary research facilities during the current research work
文摘Reducing the fuel consumption of ships presents both economic and environmental gains. Although in the past decades,extensive studies were carried out on the flow around ship hull, it is still difficult to calculate the flow around the hull while considering propeller interaction. In this paper, the viscous flow around modern ship hulls is computed considering propeller action. In this analysis, the numerical investigation of flow around the ship is combined with propeller theory to simulate the hull-propeller interaction. Various longitudinal positions of the rudder are also analyzed to determine the effect of rudder position on propeller efficiency. First, a numerical study was performed around a bare hull using Shipflow computational fluid dynamics(CFD) code to determine free-surface wave elevation and resistance components.A zonal approach was applied to successively incorporate Bpotential flow solver^ in the region outside the boundary layer and wake, Bboundary layer solver^ in the thin boundary layer region near the ship hull, and BNavier-Stokes solver^in the wake region. Propeller open water characteristics were determined using an open-source MATLAB code Open Prop, which is based on the lifting line theory, for the moderately loaded propeller. The obtained open water test results were specified in the flow module of Shipflow for self-propulsion tests. The velocity field behind the ship was recalculated into an effective wake and given to the propeller code that calculates the propeller load. Once the load was known, it was transferred to the Reynolds-averaged Navier-Stokes(RANS) solver to simulate the propeller action. The interaction between the hull and propeller with different rudder positions was then predicted to improve the propulsive efficiency.
文摘锚框结构的舰船目标检测算法存在预设锚框与真实目标框难以精准匹配的问题,设计了一种基于合成孔径雷达(Synthetic Aperture Radar,SAR)图像的无锚框实时舰船目标检测算法。该算法以YOLOX-Nano(You Only Look Once X-Nano)框架为基础,在骨干网络单元嵌入改进Ghost模块和挤压激励(Squeeze and Excitation,SE)模块。路径聚合网络(Path Aggregation Network,PANet)与改进Ghost模块和自适应空间特征融合(Adaptively Spatial Feature Fusion,ASFF)模块集成后提高了模型的特征表达能力。以输入图像分辨率为320×320像素为基准,相较于单发多框检测器(Single Shot MultiBox Detector,SSD)和YOLOv3-tiny(You Only Look Once v3-tiny)模型,实验结果显示本文算法在合成孔径雷达舰船检测数据集(SAR Ship Detection Dataset,SSDD)上平均正确率达到94.5%,参数量为0.87×10^(6),浮点计算量为0.61×10^(9),能够实现高精度和低复杂度的SAR图像舰船目标检测。
文摘在对系统功能进行总体分析的基础上,采用SQL Server 2005建立了系统所需的船型数据库。使用ASP.NET技术和集成开发工具Microsoft Visual Studio 2008,选用C#为编程语言,调用船舶设计软件Free!ship开发了基于Web的船型变换系统。研究结果表明,该系统可以方便快捷地生成船体型线,加速船舶设计进程,实现船型数据共享。
