Deng Yibin, Yang Xiaogang, Huang Yanling, Pan Tian, Zhu Han-hua
The mutual influence between the bearings of a ship's multisupport shafting makes its installation and alignment very difficult. This article addresses the problem of the calculation of the precise displacement value of each intermediate bearing and proposes a method for fitting the shafting characteristic function by using the GA-BP (genetic algorithm-back propagation) neural network. The neural network uses the intermediate bearing reaction as input to calculate the theoretical height of the bearing, thereby accurately calculating the displacement value. Taking the installation and alignment of a ro-ro ship's propulsion shafting as an application example, a neural network of the ship's shafting is established with training samples based on finite element simulation, and the effect of network training is discussed. The accuracy of the method is verified by a comparative analysis with the measured data of the ship's shafting. The calculation results of this method are used as a guide for the installation and alignment of the ship's shafting and have passed the delivery inspection of the classification society.
{"title":"Calculation Method of Intermediate Bearing Displacement Value for Multisupported Shafting Based on Neural Network","authors":"Deng Yibin, Yang Xiaogang, Huang Yanling, Pan Tian, Zhu Han-hua","doi":"10.5957/JOSR.02200007","DOIUrl":"https://doi.org/10.5957/JOSR.02200007","url":null,"abstract":"The mutual influence between the bearings of a ship's multisupport shafting makes its installation and alignment very difficult. This article addresses the problem of the calculation of the precise displacement value of each intermediate bearing and proposes a method for fitting the shafting characteristic function by using the GA-BP (genetic algorithm-back propagation) neural network. The neural network uses the intermediate bearing reaction as input to calculate the theoretical height of the bearing, thereby accurately calculating the displacement value. Taking the installation and alignment of a ro-ro ship's propulsion shafting as an application example, a neural network of the ship's shafting is established with training samples based on finite element simulation, and the effect of network training is discussed. The accuracy of the method is verified by a comparative analysis with the measured data of the ship's shafting. The calculation results of this method are used as a guide for the installation and alignment of the ship's shafting and have passed the delivery inspection of the classification society.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":"1 1","pages":"1-7"},"PeriodicalIF":1.4,"publicationDate":"2020-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46526234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the present work, a Reynolds-Averaged Navier-Stokes (RANS)-overset method is used to numerically investigate self-propulsion and turning circle maneuver in waves for a container ship. A computational fluid dynamics (CFD) solver naoe-FOAM-SJTU is used for the numerical computations of the fully appended Duisburg Test Case ship model. Overset grids are used to handle themotions of the ship hull appendedwith the propeller and the rudder. Open source toolbox waves2Foam is used to prevent wave reflection in the computational domain. The current numerical method is validated by comparing the ship speed in the self-propulsion case between CFD and Experimental Fluid Dynamics (EFD). Predicted ship 6-DOF motions, hydrodynamic forces, free surfaces, and inflow of the propeller are presented. The propulsion characteristic is mainly studied. Assuming the thrust identification method works even in unsteady conditions, the wake fraction and propulsion efficiency are discussed. The effect of orbital motion of water particle and ship motion on the propulsion performance are identified. In conclusion, the present RANS-overset method is a reliable approach to directly simulate self-propulsion and turning circle maneuver in waves.
本文采用reynolds - average Navier-Stokes (RANS)-overset方法对集装箱船在波浪中自推进和回转机动进行了数值研究。采用计算流体力学(CFD)求解器naoe-FOAM-SJTU对全附加杜伊斯堡试验船模型进行了数值计算。倒置网格是用来处理船体的运动附加的螺旋桨和方向舵。开源工具箱waves2Foam用于防止计算域中的波反射。通过CFD和实验流体动力学(EFD)对自推进情况下船舶航速的比较，验证了现有数值方法的有效性。给出了预测的船舶六自由度运动、水动力、自由面和螺旋桨入流。主要研究了其推进特性。假设推力识别方法即使在非定常条件下也有效，讨论了尾流分数和推进效率。确定了水粒子轨道运动和船舶运动对推进性能的影响。综上所述，本文提出的ranss -overset方法是直接模拟船舶在波浪中自推进和回转机动的可靠方法。
{"title":"CFD Simulations of Self-Propulsion and Turning Circle Maneuver up to 90º of Ship in Waves","authors":"Cong Liu, Jianhua Wang, D. Wan","doi":"10.5957/JOSR.09180083","DOIUrl":"https://doi.org/10.5957/JOSR.09180083","url":null,"abstract":"In the present work, a Reynolds-Averaged Navier-Stokes (RANS)-overset method is used to numerically investigate self-propulsion and turning circle maneuver in waves for a container ship. A computational fluid dynamics (CFD) solver naoe-FOAM-SJTU is used for the numerical computations of the fully appended Duisburg Test Case ship model. Overset grids are used to handle themotions of the ship hull appendedwith the propeller and the rudder. Open source toolbox waves2Foam is used to prevent wave reflection in the computational domain. The current numerical method is validated by comparing the ship speed in the self-propulsion case between CFD and Experimental Fluid Dynamics (EFD). Predicted ship 6-DOF motions, hydrodynamic forces, free surfaces, and inflow of the propeller are presented. The propulsion characteristic is mainly studied. Assuming the thrust identification method works even in unsteady conditions, the wake fraction and propulsion efficiency are discussed. The effect of orbital motion of water particle and ship motion on the propulsion performance are identified. In conclusion, the present RANS-overset method is a reliable approach to directly simulate self-propulsion and turning circle maneuver in waves.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":"1 1","pages":"1-14"},"PeriodicalIF":1.4,"publicationDate":"2020-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42910595","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hull optimization design based on computational fluid dynamics (CFD) is a highly computationally intensive complex engineering problem. Because of reasons such as many variables, spatially complex design performance, and huge computational workload, hull optimization efficiency is low. To improve the efficiency of hull optimization, a dynamic space reduction method based on a partial correlation analysis is proposed in this study. The proposed method dynamically uses hull-form optimization data to analyze and reduce the range of values for relevant design variables and, thus, considerably improves the optimization efficiency. This method is used to optimize the wave-making resistance of an S60 hull, and its feasibility is verified through comparison. 1. Introduction In recent years, to promote the rapid development of green ships, hull optimization methods based on computational fluid dynamics (CFD) have been widely used by many researchers, such as Tahara et al. (2011), Peri and Diez (2013), Kim and Yang (2010), Yang and Huang (2016), Chang et al. (2012), and Feng et al. (2009). However, hull optimization design is a typically complex engineering problem. It requires many numerical simulation calculations, and the design performance space is complex, which has resulted in low optimization efficiency and difficulty in obtaining a global optimal solution. Commonly used solutions include 1) efficient optimization algorithms, 2) approximate model techniques, and 3) high-performance cluster computers. However, these methods still cannot satisfy the engineering application requirements in terms of efficiency and quality of the solution. To solve the problem of low optimization efficiency and difficulty in obtaining an optimal solution in engineering optimization problems, many scholars have conducted research on design space reduction technology. Reungsinkonkarn and Apirukvorapinit (2014) applied the search space reduction (SSR) algorithm to the particle swarm optimization (PSO) algorithm, eliminating areas in which optimal solutions may not be found through SSR to improve the optimization efficiency of the algorithm. Chen et al. (2015) and Diez et al. (2014, 2015) used the Karhunen–Loeve expansion to evaluate the hull, eliminating the less influential factors to achieve space reduction modeling with fewer design variables. Further extensions to nonlinear dimensionality reduction methods can be found in D'Agostino et al. (2017) and Serani et al. (2019). Jeong et al. (2005) applied space reduction techniques to the aerodynamic shape optimization of the vane wheel, using the rough set theory and decision trees to extract aerofoil design rules to improve each target. Gao et al. (2009) and Wang et al. (2014) solved the problem of low optimization efficiency in the aerodynamic shape optimization design of an aircraft, by using analysis results of partial correlation, which reduced the range of values of relevant design variables to reconstruct the optim
{"title":"Application of Dynamic Space Reduction Method Based on Partial Correlation Analysis in Hull Optimization","authors":"Qiang Zheng, Haichao Chang, Zuyuan Liu, Baiwei Feng","doi":"10.5957/JOSR.04190019","DOIUrl":"https://doi.org/10.5957/JOSR.04190019","url":null,"abstract":"Hull optimization design based on computational fluid dynamics (CFD) is a highly computationally intensive complex engineering problem. Because of reasons such as many variables, spatially complex design performance, and huge computational workload, hull optimization efficiency is low. To improve the efficiency of hull optimization, a dynamic space reduction method based on a partial correlation analysis is proposed in this study. The proposed method dynamically uses hull-form optimization data to analyze and reduce the range of values for relevant design variables and, thus, considerably improves the optimization efficiency. This method is used to optimize the wave-making resistance of an S60 hull, and its feasibility is verified through comparison.\u0000 1. Introduction\u0000 In recent years, to promote the rapid development of green ships, hull optimization methods based on computational fluid dynamics (CFD) have been widely used by many researchers, such as Tahara et al. (2011), Peri and Diez (2013), Kim and Yang (2010), Yang and Huang (2016), Chang et al. (2012), and Feng et al. (2009). However, hull optimization design is a typically complex engineering problem. It requires many numerical simulation calculations, and the design performance space is complex, which has resulted in low optimization efficiency and difficulty in obtaining a global optimal solution. Commonly used solutions include 1) efficient optimization algorithms, 2) approximate model techniques, and 3) high-performance cluster computers. However, these methods still cannot satisfy the engineering application requirements in terms of efficiency and quality of the solution.\u0000 To solve the problem of low optimization efficiency and difficulty in obtaining an optimal solution in engineering optimization problems, many scholars have conducted research on design space reduction technology. Reungsinkonkarn and Apirukvorapinit (2014) applied the search space reduction (SSR) algorithm to the particle swarm optimization (PSO) algorithm, eliminating areas in which optimal solutions may not be found through SSR to improve the optimization efficiency of the algorithm. Chen et al. (2015) and Diez et al. (2014, 2015) used the Karhunen–Loeve expansion to evaluate the hull, eliminating the less influential factors to achieve space reduction modeling with fewer design variables. Further extensions to nonlinear dimensionality reduction methods can be found in D'Agostino et al. (2017) and Serani et al. (2019). Jeong et al. (2005) applied space reduction techniques to the aerodynamic shape optimization of the vane wheel, using the rough set theory and decision trees to extract aerofoil design rules to improve each target. Gao et al. (2009) and Wang et al. (2014) solved the problem of low optimization efficiency in the aerodynamic shape optimization design of an aircraft, by using analysis results of partial correlation, which reduced the range of values of relevant design variables to reconstruct the optim","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":"1 1","pages":"1-12"},"PeriodicalIF":1.4,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42241000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To meet the demand of automatic production, the multisquare punch forming has been improved to process complex curved plates. However, the improved forming equipment improves the processing quality to the maximum extent, and springback and residual stresses are inevitable phenomena in the cold bending process. Residual stress is an important factor that causes fatigue crack and stress corrosion crack. And the residual stress in machining will seriously affect the fatigue life of cold-pressed parts. Therefore, it is necessary to quantitatively and qualitatively analyze the residual stress caused by the cold forming equipment. Through theoretical derivation and finite element simulation methods, the residual stress distribution for thick plates in the cold forming process was analyzed and compared in this article. Meanwhile, the variation law of residual stress peak with thickness and forming radius was further discussed. The results show that the residual stress distributions obtained by the two theoretical models are in good agreement with the numerical results. The maximum error of peak residual stress is about 10%, which verifies the reliability of theoretical formulas. 1. Introduction A large number of complex curved sheet metal parts are used in aerospace, marine structure, automobile, and other manufacturing industries, which makes the processing and forming of complex curved sheet metal parts attract much attention. In the process of ship construction, the forming and processing of hull plates is an important part of the low intelligence, time-consuming, and serious constraint on shipbuilding automation. Strictly speaking, most of the parts in the hull plate are three-dimensional curved surfaces, most of which are composed of complex undevelopable spatial curved surfaces. It is a very difficult and urgent key technology to process a ship's steel plate into complex three-dimensional curved surface shapes. such as saddle shape or sailed shape (see Fig. 1A), to create a streamlined outer body of the ship. For many years, bending of plates with complex curvatures has been carried out by manual operation, i.e., the combination of heat line forming and rolling bending (see Fig. 1B). However, the production efficiency of the thermoforming process is relatively low, and environmental pollution is relatively serious with bad working conditions and high labor intensity. Moreover, the forming quality depends more on the experience of technicians, and quality cannot be guaranteed. With the increasing demand for automation, the multipoint forming equipment was developed and used for stamping and forming of curved plates.
{"title":"Prediction of Residual Stress on Cold-Formed Curvature Plates by Elastoplastic Material Model","authors":"Yue Lin, W. Shen, Lifei Song, Enqian Liu","doi":"10.5957/JOSR.10180097","DOIUrl":"https://doi.org/10.5957/JOSR.10180097","url":null,"abstract":"To meet the demand of automatic production, the multisquare punch forming has been improved to process complex curved plates. However, the improved forming equipment improves the processing quality to the maximum extent, and springback and residual stresses are inevitable phenomena in the cold bending process. Residual stress is an important factor that causes fatigue crack and stress corrosion crack. And the residual stress in machining will seriously affect the fatigue life of cold-pressed parts. Therefore, it is necessary to quantitatively and qualitatively analyze the residual stress caused by the cold forming equipment. Through theoretical derivation and finite element simulation methods, the residual stress distribution for thick plates in the cold forming process was analyzed and compared in this article. Meanwhile, the variation law of residual stress peak with thickness and forming radius was further discussed. The results show that the residual stress distributions obtained by the two theoretical models are in good agreement with the numerical results. The maximum error of peak residual stress is about 10%, which verifies the reliability of theoretical formulas.\u0000 1. Introduction\u0000 A large number of complex curved sheet metal parts are used in aerospace, marine structure, automobile, and other manufacturing industries, which makes the processing and forming of complex curved sheet metal parts attract much attention. In the process of ship construction, the forming and processing of hull plates is an important part of the low intelligence, time-consuming, and serious constraint on shipbuilding automation. Strictly speaking, most of the parts in the hull plate are three-dimensional curved surfaces, most of which are composed of complex undevelopable spatial curved surfaces. It is a very difficult and urgent key technology to process a ship's steel plate into complex three-dimensional curved surface shapes. such as saddle shape or sailed shape (see Fig. 1A), to create a streamlined outer body of the ship. For many years, bending of plates with complex curvatures has been carried out by manual operation, i.e., the combination of heat line forming and rolling bending (see Fig. 1B). However, the production efficiency of the thermoforming process is relatively low, and environmental pollution is relatively serious with bad working conditions and high labor intensity. Moreover, the forming quality depends more on the experience of technicians, and quality cannot be guaranteed. With the increasing demand for automation, the multipoint forming equipment was developed and used for stamping and forming of curved plates.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":"1 1","pages":"1-15"},"PeriodicalIF":1.4,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44262422","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To prevent the maritime traffic accidents and make scientific decision, scientific and accurate prediction of the traffic flow is useful, which has often been made by neural network. The weight updating methods have played an important role in improving the performance of neural networks. To ameliorate the oscillating phenomenon in training radial basis function (RBF) neural network, a fractional order gradient descent (GD) with momentum method for updating the weights of RBF neural network (FOGDM-RBF) is proposed. Its convergence is proved. The new algorithm is used to predict vessel traffic flow at Xiamen Port. It performs stable and converges to zero as the iteration increases. The results verify the theoretical results of the proposed algorithm such as its monotonicity and convergence. The descending curve of error values by fractional order GDM is smoother than the GD and GDM method. Error analysis shows that the algorithm can effectively accelerate the convergence speed of the GD method and improve its performance with high accuracy and validity. The influence of fractional order, number of hidden layer neurons, tide peak hours, and ship size is analyzed and compared. 1. Introduction As the world shipping becomes more and more busy, the large ship traffic flow leads to frequent maritime traffic accidents, resulting in huge economic losses. Ship traffic flow is a basic system in marine traffic engineering and an important index to measure the construction of marine traffic infrastructure. Its prediction results can provide basis for formulating scientific Port management planning and ship navigation management. Therefore, to ensure the accuracy and rationality of ship traffic flow forecasting is of great significance for improving port infrastructure construction and formulating scientific port management strategies. Many advanced artificial intelligence optimization algorithms have been used for ship traffic flow forecasting, such as artificial neural network (Zhai 2013; Zhang 2015). Neural network can deal with complex nonlinear problems and has achieved some results. However, the neural network itself has some shortcomings, such as slow learning speed, easy to fall into the local extremum, learning and memory instability, etc.
{"title":"Ship Traffic Flow Prediction Based on Fractional Order Gradient Descent with Momentum for RBF Neural Network","authors":"Xue Han","doi":"10.5957/JOSR.08190052","DOIUrl":"https://doi.org/10.5957/JOSR.08190052","url":null,"abstract":"To prevent the maritime traffic accidents and make scientific decision, scientific and accurate prediction of the traffic flow is useful, which has often been made by neural network. The weight updating methods have played an important role in improving the performance of neural networks. To ameliorate the oscillating phenomenon in training radial basis function (RBF) neural network, a fractional order gradient descent (GD) with momentum method for updating the weights of RBF neural network (FOGDM-RBF) is proposed. Its convergence is proved. The new algorithm is used to predict vessel traffic flow at Xiamen Port. It performs stable and converges to zero as the iteration increases. The results verify the theoretical results of the proposed algorithm such as its monotonicity and convergence. The descending curve of error values by fractional order GDM is smoother than the GD and GDM method. Error analysis shows that the algorithm can effectively accelerate the convergence speed of the GD method and improve its performance with high accuracy and validity. The influence of fractional order, number of hidden layer neurons, tide peak hours, and ship size is analyzed and compared.\u0000 1. Introduction\u0000 As the world shipping becomes more and more busy, the large ship traffic flow leads to frequent maritime traffic accidents, resulting in huge economic losses. Ship traffic flow is a basic system in marine traffic engineering and an important index to measure the construction of marine traffic infrastructure. Its prediction results can provide basis for formulating scientific Port management planning and ship navigation management. Therefore, to ensure the accuracy and rationality of ship traffic flow forecasting is of great significance for improving port infrastructure construction and formulating scientific port management strategies. Many advanced artificial intelligence optimization algorithms have been used for ship traffic flow forecasting, such as artificial neural network (Zhai 2013; Zhang 2015). Neural network can deal with complex nonlinear problems and has achieved some results. However, the neural network itself has some shortcomings, such as slow learning speed, easy to fall into the local extremum, learning and memory instability, etc.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":"1 1","pages":"1-8"},"PeriodicalIF":1.4,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48936000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jan Clemens Neitzel-Petersen, Sophie Juliane Stutz, M. Abdel‐Maksoud
The crash-stop maneuver of a ship equipped with two pods produces the largest loads that the structure and azimuth bearing can possibly experience. For design purposes, a sufficiently fast and accurate determination of the loads is thus critically important. This study examines load estimation during crash-stop maneuvers based on model tests and numerical methods. Forces and moments are compared to determine the influence of different control parameters (azimuth rate, propeller number of revolution, etc.). In addition, the results of numerical simulations carried out in model- and full-scale are used to analyze the influence of the Reynolds number on the flow behavior. Results show a significant influence of the azimuth rate on the maximum forces and moments. The numerical calculations indicate a strong dependency of the flow stall behavior on the azimuth rate. The dynamic stall effect on the profile-shaped parts, such as the pod strut, is shifted to a larger angle of attack compared with a steady angular position. This phenomenon is also observed during the model tests. The full-scale simulations show up to a 23% increase of the forces compared with the model-scale simulations. Thus, a detailed and careful handling of the results considered in the design process is required for the load estimation.
{"title":"Steady and Unsteady Hydrodynamic Loads on the Azimuth Bearing of a POD during a Crash-Stop Maneuver","authors":"Jan Clemens Neitzel-Petersen, Sophie Juliane Stutz, M. Abdel‐Maksoud","doi":"10.5957/JOSR.09180055","DOIUrl":"https://doi.org/10.5957/JOSR.09180055","url":null,"abstract":"The crash-stop maneuver of a ship equipped with two pods produces the largest loads that the structure and azimuth bearing can possibly experience. For design purposes, a sufficiently fast and accurate determination of the loads is thus critically important. This study examines load estimation during crash-stop maneuvers based on model tests and numerical methods. Forces and moments are compared to determine the influence of different control parameters (azimuth rate, propeller number of revolution, etc.). In addition, the results of numerical simulations carried out in model- and full-scale are used to analyze the influence of the Reynolds number on the flow behavior. Results show a significant influence of the azimuth rate on the maximum forces and moments. The numerical calculations indicate a strong dependency of the flow stall behavior on the azimuth rate. The dynamic stall effect on the profile-shaped parts, such as the pod strut, is shifted to a larger angle of attack compared with a steady angular position. This phenomenon is also observed during the model tests. The full-scale simulations show up to a 23% increase of the forces compared with the model-scale simulations. Thus, a detailed and careful handling of the results considered in the design process is required for the load estimation.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":"65 1","pages":"25-40"},"PeriodicalIF":1.4,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42650981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hua Xianghong, Xiao Wei, Yao Xiong-liang, Gu Jiayang, Jiang Zhi-yong
Compared with the square and circle moonpools, the rectangular moonpool with a large aspect ratio is more conducive to install the equipment. To reduce fluid motion in the rectangular moonpool with a large aspect ratio, a recess is installed in the moonpool. However, the fluid motion in a recessing type moonpool with a large aspect ratio has been rarely studied. In this study, a series of experiments are carried out to investigate on the hydrodynamic characteristics of fluid in the recessing type moonpool with a large aspect ratio. To facilitate the monitoring of the fluid motions, experiments are carried out in a transparent wave channel with the model made up of transparent acrylic. According to the experiment results, there are some complicated fluid motions in the moonpool. Under the resonance condition, the fluid moves violently in the moonpool. To reduce the fluid motion in the recessing type moonpool, three damping devices including the positive grid of flaps, the negative grid of flaps, and the grid of baffles are proposed. The reduction effect of the three damping devices is investigated experimentally. The damping devices have good reduction effects at most time. The smaller the incident wave period, the better is the reduction effect. 1. Introduction The moonpools run vertically through the hull of ships or marine structures, providing a sheltered working environment under harsh ocean conditions. The fluid motion in the moonpool is similar to that in the slit between the ships or rectangular bodies (Faltinsen et al. 2007; Mavrakos & Chatjigeorgiou 2009; Ikeda et al. 2012; Chen et al. 2014; Heo et al. 2014; Zhang & Bandyk 2014; Faltinsen & Timokha 2015; Yu et al. 2017; Gao et al. 2019d). Two dominant types of fluid motions, the piston motion and the sloshing motion, are discussed (Fukuda 1977; Molin 2001; McIver 2005; Kristiansen & Faltinsen 2012; Zhou & Zhang 2013).
与方形和圆形月池相比，长宽比大的矩形月池更有利于设备的安装。为了减少具有大纵横比的矩形月池中的流体运动，在月池中安装了凹槽。然而，对于大纵横比凹陷型月池流体运动的研究却很少。本文通过一系列实验研究了大纵横比凹坑型月池中流体的水动力特性。为了便于对流体运动进行监测，实验采用透明亚克力制成的透明波槽模型。实验结果表明，月池中存在着复杂的流体运动。在共振条件下，流体在月池中剧烈运动。为了减小凹坑式月池中的流体运动，提出了三种阻尼装置:挡板正栅格、挡板负栅格和挡板栅格。实验研究了三种阻尼装置的减振效果。阻尼装置在大多数情况下具有良好的减震效果。入射波周期越小，减振效果越好。1. 月球池垂直穿过船舶或海洋结构物的船体，在恶劣的海洋条件下提供一个隐蔽的工作环境。月池中的流体运动与船舶或矩形体之间的狭缝中的流体运动相似(Faltinsen et al. 2007;Mavrakos & Chatjigeorgiou 2009;Ikeda et al. 2012;Chen et al. 2014;Heo et al. 2014;Zhang & Bandyk 2014;Faltinsen & Timokha 2015;Yu et al. 2017;Gao et al. 2019d)。讨论了流体运动的两种主要类型，活塞运动和晃动运动(Fukuda 1977;Molin 2001;McIver 2005;Kristiansen & Faltinsen 2012;Zhou & Zhang 2013)。
{"title":"An Experimental Investigation on Reduction Effect of Damping Devices for the Recessing Type Moonpool with a Large Aspect Ratio","authors":"Hua Xianghong, Xiao Wei, Yao Xiong-liang, Gu Jiayang, Jiang Zhi-yong","doi":"10.5957/JOSR.08190045","DOIUrl":"https://doi.org/10.5957/JOSR.08190045","url":null,"abstract":"Compared with the square and circle moonpools, the rectangular moonpool with a large aspect ratio is more conducive to install the equipment. To reduce fluid motion in the rectangular moonpool with a large aspect ratio, a recess is installed in the moonpool. However, the fluid motion in a recessing type moonpool with a large aspect ratio has been rarely studied. In this study, a series of experiments are carried out to investigate on the hydrodynamic characteristics of fluid in the recessing type moonpool with a large aspect ratio. To facilitate the monitoring of the fluid motions, experiments are carried out in a transparent wave channel with the model made up of transparent acrylic. According to the experiment results, there are some complicated fluid motions in the moonpool. Under the resonance condition, the fluid moves violently in the moonpool. To reduce the fluid motion in the recessing type moonpool, three damping devices including the positive grid of flaps, the negative grid of flaps, and the grid of baffles are proposed. The reduction effect of the three damping devices is investigated experimentally. The damping devices have good reduction effects at most time. The smaller the incident wave period, the better is the reduction effect.\u0000 1. Introduction\u0000 The moonpools run vertically through the hull of ships or marine structures, providing a sheltered working environment under harsh ocean conditions. The fluid motion in the moonpool is similar to that in the slit between the ships or rectangular bodies (Faltinsen et al. 2007; Mavrakos & Chatjigeorgiou 2009; Ikeda et al. 2012; Chen et al. 2014; Heo et al. 2014; Zhang & Bandyk 2014; Faltinsen & Timokha 2015; Yu et al. 2017; Gao et al. 2019d). Two dominant types of fluid motions, the piston motion and the sloshing motion, are discussed (Fukuda 1977; Molin 2001; McIver 2005; Kristiansen & Faltinsen 2012; Zhou & Zhang 2013).","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":"1 1","pages":"1-20"},"PeriodicalIF":1.4,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47638376","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Li Xiong, Haibo Gao, R. Norman, K. Pazouki, Z. Lin, Serena Lim
Unmanned surface vehicles (USVs) are vessels that operate without any crew onboard. There is an increased demand for USVs in recent years, particularly for the use of water quality monitoring and ocean data mapping. In China, USVs are widely used as a luring fish boat which acts as the assisting boat of light luring seine vessel. One of the main problems of such boat is that the traditional propulsion system is poorly matched with the high energy consumption that is required during certain specific operation, which results in poor vessel performance. A hybrid electric propulsion system configuration solution is proposed to increase the overall propulsion efficiency of such USVs. The typical operating profile was identified and a comprehensive simulation was conducted to demonstrate the compatibility during vessel operations. An intelligent equipment selection analysis was also carried out to recommend the optimal equipment selection by considering a multiobjective problem. The result shows that the configuration solution proposed can reduce fuel consumption and the optimal intelligent selection method can provide a suitable selection solution for decision makers. This article highlights an energy management strategy focusing on the threshold method based on support vector machine pattern recognition. A multiobjective particle swarm optimization algorithm based on the dynamic inertia weight and chaotic motion was used to optimize the equipment selection by considering fuel consumption and emissions. The proposed propulsion system configuration and equipment selection solution can be implemented for the design of USVs, which has a routine fixed operating pattern.
{"title":"Optimal Design of Propulsion System Configuration for Electrically Propelled Unmanned Surface Vehicle","authors":"Li Xiong, Haibo Gao, R. Norman, K. Pazouki, Z. Lin, Serena Lim","doi":"10.5957/JOSR.01190001","DOIUrl":"https://doi.org/10.5957/JOSR.01190001","url":null,"abstract":"Unmanned surface vehicles (USVs) are vessels that operate without any crew onboard. There is an increased demand for USVs in recent years, particularly for the use of water quality monitoring and ocean data mapping. In China, USVs are widely used as a luring fish boat which acts as the assisting boat of light luring seine vessel. One of the main problems of such boat is that the traditional propulsion system is poorly matched with the high energy consumption that is required during certain specific operation, which results in poor vessel performance. A hybrid electric propulsion system configuration solution is proposed to increase the overall propulsion efficiency of such USVs. The typical operating profile was identified and a comprehensive simulation was conducted to demonstrate the compatibility during vessel operations. An intelligent equipment selection analysis was also carried out to recommend the optimal equipment selection by considering a multiobjective problem. The result shows that the configuration solution proposed can reduce fuel consumption and the optimal intelligent selection method can provide a suitable selection solution for decision makers. This article highlights an energy management strategy focusing on the threshold method based on support vector machine pattern recognition. A multiobjective particle swarm optimization algorithm based on the dynamic inertia weight and chaotic motion was used to optimize the equipment selection by considering fuel consumption and emissions. The proposed propulsion system configuration and equipment selection solution can be implemented for the design of USVs, which has a routine fixed operating pattern.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":"65 1","pages":"1-10"},"PeriodicalIF":1.4,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46594779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Michael I. Foteinos, George I. Christofilis, N. Kyrtatos
The transient performance of a direct-drive large two-stroke marine diesel engine, installed in a vessel operating in a seaway with heavy weather, is investigated via simulation. The main engine of the ship is equipped with a selective catalytic reduction (SCR) after treatment system for compliance with the latest International Maritime Organization (IMO) rules for NOx reduction, IMO Tier III. Because of limitations of exhaust gas temperature at the inlet of SCR systems and the low temperature exhaust gases produced by marine diesel engines, in marine applications, the SCR system is installed on the high-pressure side of the turbine. When a ship sails in heavy weather, it experiences a resistance increase, wave-induced motions, and a time-varying flow field in the propeller, induced by ship motions. This results in a fluctuation of the propeller torque demand and, thus, a fluctuation in engine power and exhaust gas temperature, which can affect engine and SCR performance. To investigate this phenomenon and take into account the engine–propeller interaction, the entire propulsion plant was modeled, namely, the slow-speed diesel propulsion engine, the high-pressure SCR system, the directly driven propeller, and the ship's hull. To simulate the transient propeller torque demand, a propeller model was used, and torque variations due to ship motions were taken into account. Ship motions in waves and wave-added resistance were calculated for regular and irregular waves using a 3D panel code. The coupled model was validated against available measured data from a shipboard propulsion system in good weather conditions. The model was then used to simulate the behavior of a Tier III marine propulsion plant during acceleration from low to medium load, in the presence of regular and irregular waves. The effect of the time-varying propeller demand on the engine and the SCR system was investigated. 1. Introduction The effect of waves on a marine propulsion system is a complex phenomenon involving interactions between different subsystems of the propulsion plant, i.e., the prime mover, the propeller, and the ship's hull. Ships sailing in heavy weather conditions experience a resistance increase, wave-induced motions, and a time-varying flow field in the propeller. This leads to a fluctuation of the propeller torque demand which results in a fluctuation in engine-produced power and exhaust gas temperature.
{"title":"Large Two-Stroke Marine Diesel Engine Operation with a High-Pressure SCR System in Heavy Weather Conditions","authors":"Michael I. Foteinos, George I. Christofilis, N. Kyrtatos","doi":"10.5957/JOSR.05190027","DOIUrl":"https://doi.org/10.5957/JOSR.05190027","url":null,"abstract":"The transient performance of a direct-drive large two-stroke marine diesel engine, installed in a vessel operating in a seaway with heavy weather, is investigated via simulation. The main engine of the ship is equipped with a selective catalytic reduction (SCR) after treatment system for compliance with the latest International Maritime Organization (IMO) rules for NOx reduction, IMO Tier III. Because of limitations of exhaust gas temperature at the inlet of SCR systems and the low temperature exhaust gases produced by marine diesel engines, in marine applications, the SCR system is installed on the high-pressure side of the turbine. When a ship sails in heavy weather, it experiences a resistance increase, wave-induced motions, and a time-varying flow field in the propeller, induced by ship motions. This results in a fluctuation of the propeller torque demand and, thus, a fluctuation in engine power and exhaust gas temperature, which can affect engine and SCR performance. To investigate this phenomenon and take into account the engine–propeller interaction, the entire propulsion plant was modeled, namely, the slow-speed diesel propulsion engine, the high-pressure SCR system, the directly driven propeller, and the ship's hull. To simulate the transient propeller torque demand, a propeller model was used, and torque variations due to ship motions were taken into account. Ship motions in waves and wave-added resistance were calculated for regular and irregular waves using a 3D panel code. The coupled model was validated against available measured data from a shipboard propulsion system in good weather conditions. The model was then used to simulate the behavior of a Tier III marine propulsion plant during acceleration from low to medium load, in the presence of regular and irregular waves. The effect of the time-varying propeller demand on the engine and the SCR system was investigated.\u0000 1. Introduction\u0000 The effect of waves on a marine propulsion system is a complex phenomenon involving interactions between different subsystems of the propulsion plant, i.e., the prime mover, the propeller, and the ship's hull. Ships sailing in heavy weather conditions experience a resistance increase, wave-induced motions, and a time-varying flow field in the propeller. This leads to a fluctuation of the propeller torque demand which results in a fluctuation in engine-produced power and exhaust gas temperature.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":" ","pages":"1-15"},"PeriodicalIF":1.4,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44795557","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Whirling vibration is an important part of the calculations of the design of a marine shaft. In fact, all classification societies require a propulsion shafting whirling vibration calculation giving the range of critical speeds, i.e., free whirling vibration calculation. However, whirling vibration is a source of fatigue failure of the bracket and aft stern tube bearings, destruction of high-speed shafts with universal joints, noise, and hull vibrations. There are numerous uncertainties in the calculation of whirling vibration, namely, in the shafting system modeling and in the determination of excitement and damping forces. Moreover, whirling vibration calculation mathematics is much more complex than torsional or axial calculations. The marine propulsion shaft can be studied as a selfsustained vibration system, which can be modeled using the Van der Pol equation. In this document, a new way to solve the Van der pol equation is presented. The proposed method, based on a variational approach without local minima extra to the solution, converges for whatever initial point and parameter in the Van der Pol equation.
{"title":"Marine Propulsion Shafting: A Study of Whirling Vibrations","authors":"M. J. Legaz, S. Amat, S. Busquier","doi":"10.5957/JOSR.05180022","DOIUrl":"https://doi.org/10.5957/JOSR.05180022","url":null,"abstract":"Whirling vibration is an important part of the calculations of the design of a marine shaft. In fact, all classification societies require a propulsion shafting whirling vibration calculation giving the range of critical speeds, i.e., free whirling vibration calculation. However, whirling vibration is a source of fatigue failure of the bracket and aft stern tube bearings, destruction of high-speed shafts with universal joints, noise, and hull vibrations. There are numerous uncertainties in the calculation of whirling vibration, namely, in the shafting system modeling and in the determination of excitement and damping forces. Moreover, whirling vibration calculation mathematics is much more complex than torsional or axial calculations. The marine propulsion shaft can be studied as a selfsustained vibration system, which can be modeled using the Van der Pol equation. In this document, a new way to solve the Van der pol equation is presented. The proposed method, based on a variational approach without local minima extra to the solution, converges for whatever initial point and parameter in the Van der Pol equation.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":"65 1","pages":"1-7"},"PeriodicalIF":1.4,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43159002","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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