A stepped planing hull is a type of high-speed boat with a transverse break in the bottom of the hull. The step allows the hull to run at a higher trim angle, and also reduces the wetted surface area at planing speeds because of a pocket of air that forms aft of the step, often reducing the frictional resistance. This paper summarizes model tests that were conducted on a prismatic planing hull, with two adjustable stern sections, to form either a single- or twin-step planing hull. Measurements were made of the resistance, heave, wetted lengths, and cavity pressures behind the steps for various speeds at fixed trim. The ventilation cases included natural ventilation, augmented ventilated by means of vent tubes located behind the step, and reduced ventilation, where the flow was blocked off from the step by closing the vent tubes and adding longitudinal fences to either chine to prevent air inflow. Blocking off the ventilation causes negative pressures to form and increases resistance. Tests conducted in waves showed that the size of the ventilation cavity behind a step is not affected significantly by small waves, indicating a shielding effect of the hull. Stepped hulls are becoming increasingly commonplace in high-speed craft for both military and recreational purposes. A stepped hull is a type of planing boat, in which there is a discontinuity in the bottom, resulting in flow separating from the step and reattaching father aft along the hull. This feature can reduce resistance in some cases. Although they’ve been in use for over a century, they remain a challenge to design and to physically model.
{"title":"Effect of Ventilation on Cavity Formation on Stepped Planing Hulls","authors":"Andrew Ricks, M. Morabito, R. Datla","doi":"10.5957/josr.05200032","DOIUrl":"https://doi.org/10.5957/josr.05200032","url":null,"abstract":"A stepped planing hull is a type of high-speed boat with a transverse break in the bottom of the hull. The step allows the hull to run at a higher trim angle, and also reduces the wetted surface area at planing speeds because of a pocket of air that forms aft of the step, often reducing the frictional resistance. This paper summarizes model tests that were conducted on a prismatic planing hull, with two adjustable stern sections, to form either a single- or twin-step planing hull. Measurements were made of the resistance, heave, wetted lengths, and cavity pressures behind the steps for various speeds at fixed trim. The ventilation cases included natural ventilation, augmented ventilated by means of vent tubes located behind the step, and reduced ventilation, where the flow was blocked off from the step by closing the vent tubes and adding longitudinal fences to either chine to prevent air inflow. Blocking off the ventilation causes negative pressures to form and increases resistance. Tests conducted in waves showed that the size of the ventilation cavity behind a step is not affected significantly by small waves, indicating a shielding effect of the hull.\u0000 \u0000 \u0000 Stepped hulls are becoming increasingly commonplace in high-speed craft for both military and recreational purposes. A stepped hull is a type of planing boat, in which there is a discontinuity in the bottom, resulting in flow separating from the step and reattaching father aft along the hull. This feature can reduce resistance in some cases. Although they’ve been in use for over a century, they remain a challenge to design and to physically model.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41728039","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}
Ships vulnerability analysis is one of the most important issues in today’s research, to reduce damage and increase safety. To increase the safety of ships, the effective parameters of the vulnerability of ships, the impact of each of them, and the relationship between these parameters should be identified to formulate different scenarios to analyze the vulnerability of ships. This process leads to the formation of simulation models to assess the risk of vessels. The creation of a spatial conceptual framework is needed to create integrated vulnerability models. The most important innovation of this research is the development of a spatial framework for analyzing ships’ vulnerability based on category theory. A framework that can be used to model the various scenarios of ships’ vulnerability from a variety of perspectives. To provide this framework, objects, operators, relationships, and assumptions for vulnerability analysis have been developed. To better express and convey the concepts, the spatial framework of the vulnerability analysis is presented in the form of category theory, which is a mathematical structure. The category theory is a good tool for expressing and creating a mathematical structure for objects and complex relationships in the real world, where other tools do not have this ability. The benefits of the built-in framework have been described with an integrated, precise mathematical structure that can be generalized to other subjects. Studies show that the developed framework is capable of modeling different scenarios for vulnerability analysis to find the best solution to reduce vulnerability.
{"title":"Developing a Spatial Framework for Ship Vulnerability Assessment Based on Category Theory","authors":"A. Ramezani, M. Malek","doi":"10.5957/josr.02210003","DOIUrl":"https://doi.org/10.5957/josr.02210003","url":null,"abstract":"Ships vulnerability analysis is one of the most important issues in today’s research, to reduce damage and increase safety. To increase the safety of ships, the effective parameters of the vulnerability of ships, the impact of each of them, and the relationship between these parameters should be identified to formulate different scenarios to analyze the vulnerability of ships. This process leads to the formation of simulation models to assess the risk of vessels. The creation of a spatial conceptual framework is needed to create integrated vulnerability models. The most important innovation of this research is the development of a spatial framework for analyzing ships’ vulnerability based on category theory. A framework that can be used to model the various scenarios of ships’ vulnerability from a variety of perspectives. To provide this framework, objects, operators, relationships, and assumptions for vulnerability analysis have been developed. To better express and convey the concepts, the spatial framework of the vulnerability analysis is presented in the form of category theory, which is a mathematical structure. The category theory is a good tool for expressing and creating a mathematical structure for objects and complex relationships in the real world, where other tools do not have this ability. The benefits of the built-in framework have been described with an integrated, precise mathematical structure that can be generalized to other subjects. Studies show that the developed framework is capable of modeling different scenarios for vulnerability analysis to find the best solution to reduce vulnerability.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46660554","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}
Leg placement and removal are the two most critical operational modes for dynamically positioned jack-ups when working close to an offshore asset. Any positional deviation may lead to collision and damage to the asset. The industry operates with a weak link between the dynamic positioning (DP) system and the jacking system. Current DP systems operate without any sensors identifying the hydrodynamic force variations on the legs and spudcans, which vary between different leg and spudcan designs. When the spudcan is near to the sea bottom, the hydrodynamic force must be reported to avoid large positional deviations driven by the DP system. This article promotes a mechanism to measure these forces using Computational Fluid Dynamics (CFD) analysis to analyze the jack-up behavior, when the spudcan assembly is operating close to the sea bottom. A jack-up’s dynamic positioning (DP) control system requires minimum 23–30 minutes for the mathematical model to learn the vessel’s hydrodynamic behavior and response to the environment. Although when moving between locations, DP jack-up vessels provide time for the DP model to learn the hydrodynamic behavior, the spudcan that holds the vessel position and headings does not allow the mathematical model to learn. The residual current remains constant until the spudcan is in the seabed. As a result, the DP mathematical model-building process does not help the DP system to estimate the additional forces in the form of residual current. Soon after the spudcan detaches from the seabed, the vessel drift occurs because the vessel thrusters’ response need a rapid response of thrust and azimuth (directions). The DP system manufacturers currently use a sensorless approach to account for the hydrodynamic forces on the legs and spudcans to build a factor into the mathematical model. The jack-up DP system addresses two simultaneous forces on the legs. The leg element in the air is subject to aerodynamic effects and the leg and spudcan elements in the water are subject to hydrodynamic effects. DP systems currently use drag coefficients (Cd) to compute drag forces, however the hydrodynamic force variations during the complete lowering and raising processes are never completely considered. This weak link in the overall operation leads to positional error and is generally unrecognized by the vessel operators. The risk falls to DP officer and the jacking master to handle. The DP and jacking simultaneous operations mode (SIMOPS) may easily last between 15 and 90 minutes, depending on jacking speed, operational water depth, and field procedures, on approach to the asset. The area of operation is close to the asset, which increases the risk of collision with the asset. Most of the studies on jack-up vessels focus on impact force acting on the leg during touchdown or penetrations, such as Elkadi et al. (2014) and Kreuzer et al. (2014).
{"title":"Hydrodynamic Forces of DP Jack-Up Leg when Operating in Vicinity of Seabed","authors":"Nitin D. Thulkar, S. Yamaguchi","doi":"10.5957/josr.03200020","DOIUrl":"https://doi.org/10.5957/josr.03200020","url":null,"abstract":"\u0000 \u0000 Leg placement and removal are the two most critical operational modes for dynamically positioned jack-ups when working close to an offshore asset. Any positional deviation may lead to collision and damage to the asset. The industry operates with a weak link between the dynamic positioning (DP) system and the jacking system. Current DP systems operate without any sensors identifying the hydrodynamic force variations on the legs and spudcans, which vary between different leg and spudcan designs. When the spudcan is near to the sea bottom, the hydrodynamic force must be reported to avoid large positional deviations driven by the DP system. This article promotes a mechanism to measure these forces using Computational Fluid Dynamics (CFD) analysis to analyze the jack-up behavior, when the spudcan assembly is operating close to the sea bottom.\u0000 \u0000 \u0000 \u0000 A jack-up’s dynamic positioning (DP) control system requires minimum 23–30 minutes for the mathematical model to learn the vessel’s hydrodynamic behavior and response to the environment. Although when moving between locations, DP jack-up vessels provide time for the DP model to learn the hydrodynamic behavior, the spudcan that holds the vessel position and headings does not allow the mathematical model to learn. The residual current remains constant until the spudcan is in the seabed. As a result, the DP mathematical model-building process does not help the DP system to estimate the additional forces in the form of residual current. Soon after the spudcan detaches from the seabed, the vessel drift occurs because the vessel thrusters’ response need a rapid response of thrust and azimuth (directions). The DP system manufacturers currently use a sensorless approach to account for the hydrodynamic forces on the legs and spudcans to build a factor into the mathematical model. The jack-up DP system addresses two simultaneous forces on the legs. The leg element in the air is subject to aerodynamic effects and the leg and spudcan elements in the water are subject to hydrodynamic effects. DP systems currently use drag coefficients (Cd) to compute drag forces, however the hydrodynamic force variations during the complete lowering and raising processes are never completely considered. This weak link in the overall operation leads to positional error and is generally unrecognized by the vessel operators. The risk falls to DP officer and the jacking master to handle. The DP and jacking simultaneous operations mode (SIMOPS) may easily last between 15 and 90 minutes, depending on jacking speed, operational water depth, and field procedures, on approach to the asset. The area of operation is close to the asset, which increases the risk of collision with the asset. Most of the studies on jack-up vessels focus on impact force acting on the leg during touchdown or penetrations, such as Elkadi et al. (2014) and Kreuzer et al. (2014).\u0000","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48927769","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}
With the effects of global warming, the North Sea Route has become an economic option for cargo transportation because of the shorter distance between East Asia and Europe. Generally, conventional mechanical propulsion systems installed in ice-capable tankers suffer from significant drawbacks because of poor fuel efficiency when sailing at low speed, therefore, advanced technologies have been applied such as diesel electric and nuclear-powered propulsion; however, drawbacks still exist. Hybrid propulsion is a more environmental-friendly, economical solution for ships with icebreaking capability, which can address the drawbacks in both diesel electric and nuclear power systems. In this paper, modeling of system components is presented and implemented in MATLAB Simulink. A primary control strategy is applied to the system to ensure system stability, and an advanced secondary strategy is developed and applied to the power sources to minimize fuel consumption. Given two scenarios, the simulation results of the hybrid propulsion system developed in this research and those of diesel electric propulsion systems with DC and AC distribution systems are compared and indicate that the hybrid system can offer up to 22.4% fuel savings over ice-loading condition, and 39.5% fuel reduction over the particular voyage of varying speed in open water is applied in this paper. In recent years, some sea routes that were previously blocked by ice have become increasingly accessible in the warmest months of the year due to the effects of global warming. Researchers have estimated that, by 2030, the percentage of Arctic shipping will have increased to 25% of cargo trade between Europe and Asia (Lasserre 2019). Northern Sea Route (NSR) shipping provides benefits for international trade, but challenges still exist. Increasing carbon emissions have seriously impacted the Arctic environment (Hassol & Corell 2006). Table 1 shows the total number of ships using Heavy Fuel Oil (HFO) in Arctic waters in 2015, and associated black carbon emissions, as published by the IMO (Comer et al. 2017). As it is shown, oil tankers made up just 4.5% of all ships entering Arctic waters but despite their low proportion, they were responsible for 17% of black carbon emissions. Thus, an environmentally friendly and fuel-efficient propulsion system to reduce these emissions from tankers trading in Arctic waters is required.
{"title":"The Modeling and Optimal Control of a Hybrid Propulsion System for an Ice-Capable Tanker","authors":"Yi Zhou, K. Pazouki, R. Norman","doi":"10.5957/josr.11200059","DOIUrl":"https://doi.org/10.5957/josr.11200059","url":null,"abstract":"\u0000 \u0000 With the effects of global warming, the North Sea Route has become an economic option for cargo transportation because of the shorter distance between East Asia and Europe. Generally, conventional mechanical propulsion systems installed in ice-capable tankers suffer from significant drawbacks because of poor fuel efficiency when sailing at low speed, therefore, advanced technologies have been applied such as diesel electric and nuclear-powered propulsion; however, drawbacks still exist. Hybrid propulsion is a more environmental-friendly, economical solution for ships with icebreaking capability, which can address the drawbacks in both diesel electric and nuclear power systems. In this paper, modeling of system components is presented and implemented in MATLAB Simulink. A primary control strategy is applied to the system to ensure system stability, and an advanced secondary strategy is developed and applied to the power sources to minimize fuel consumption. Given two scenarios, the simulation results of the hybrid propulsion system developed in this research and those of diesel electric propulsion systems with DC and AC distribution systems are compared and indicate that the hybrid system can offer up to 22.4% fuel savings over ice-loading condition, and 39.5% fuel reduction over the particular voyage of varying speed in open water is applied in this paper.\u0000 \u0000 \u0000 \u0000 In recent years, some sea routes that were previously blocked by ice have become increasingly accessible in the warmest months of the year due to the effects of global warming. Researchers have estimated that, by 2030, the percentage of Arctic shipping will have increased to 25% of cargo trade between Europe and Asia (Lasserre 2019).\u0000 Northern Sea Route (NSR) shipping provides benefits for international trade, but challenges still exist. Increasing carbon emissions have seriously impacted the Arctic environment (Hassol & Corell 2006). Table 1 shows the total number of ships using Heavy Fuel Oil (HFO) in Arctic waters in 2015, and associated black carbon emissions, as published by the IMO (Comer et al. 2017). As it is shown, oil tankers made up just 4.5% of all ships entering Arctic waters but despite their low proportion, they were responsible for 17% of black carbon emissions. Thus, an environmentally friendly and fuel-efficient propulsion system to reduce these emissions from tankers trading in Arctic waters is required.\u0000","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49376197","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 this article, a multilabel support vector machine (SVM)-based approach is investigated to address the simultaneous decay detection of the marine propulsion system. To verify the performance of the algorithm, we perform some experiments using a simulation dataset from a real-data validated numerical simulator of a Frigate. In particular, we try to train the model without simultaneous decay data, considering the great difficulty of obtaining simultaneous decay data in practice. The experimental results show that the proposed approach can identify the complex decay modes of the marine propulsion system effectively using only simple decay data in the training process. Introduction The propulsion system is considered to be the “heart” of a marine ship (Li et al. 2019a). Its safety and reliability are critical to the regular operation of the ship (Bayer et al. 2018; Cheliotis & Lazakis, 2018; Lazakis et al. 2016). However, performance decay may occur to the propulsion system due to the high humidity and high salt characteristics of the marine environment (Fang et al. 2018; Kang et al. 2019; Wang et al. 2019). The decay modes can be divided into single decay and simultaneous decay. Single decay indicates a simple decay mode that only one kind of decay occurs at a time, and simultaneous decay indicates a complex decay mode that multiple decays occur at the same time. To improve the safety and reliability of the marine propulsion system, researchers have proposed many related approaches from the perspective of fault diagnosis.
本文研究了一种基于多标签支持向量机(SVM)的船舶推进系统同步衰减检测方法。为了验证该算法的性能，我们使用护卫舰实际数据验证数值模拟器的仿真数据集进行了一些实验。考虑到实际中获取同步衰减数据的难度很大，我们尝试在没有同步衰减数据的情况下训练模型。实验结果表明，该方法在训练过程中仅使用简单的衰减数据就能有效识别舰船推进系统的复杂衰减模式。推进系统被认为是船舶的“心脏”(Li et al. 2019a)。其安全性和可靠性对船舶的正常运行至关重要(Bayer et al. 2018;Cheliotis & Lazakis, 2018;Lazakis et al. 2016)。然而，由于海洋环境的高湿和高盐特性，推进系统可能会出现性能衰减(Fang et al. 2018;Kang et al. 2019;Wang et al. 2019)。衰减模式可分为单次衰减和同步衰减。单一衰变是指一次只发生一种衰变的简单衰变模式，同时衰变是指同时发生多种衰变的复杂衰变模式。为了提高船舶推进系统的安全性和可靠性，研究人员从故障诊断的角度提出了许多相关的方法。
{"title":"Complex Decay Prediction of Marine Machinery Using Multilabel SVM","authors":"Yanghui Tan, Hui Tian, Feixiang Xu, Dingyu Jiang, Ruizheng Jiang, Yejin Lin, Jun-dong Zhang","doi":"10.5957/josr.10200052","DOIUrl":"https://doi.org/10.5957/josr.10200052","url":null,"abstract":"In this article, a multilabel support vector machine (SVM)-based approach is investigated to address the simultaneous decay detection of the marine propulsion system. To verify the performance of the algorithm, we perform some experiments using a simulation dataset from a real-data validated numerical simulator of a Frigate. In particular, we try to train the model without simultaneous decay data, considering the great difficulty of obtaining simultaneous decay data in practice. The experimental results show that the proposed approach can identify the complex decay modes of the marine propulsion system effectively using only simple decay data in the training process.\u0000 Introduction\u0000 The propulsion system is considered to be the “heart” of a marine ship (Li et al. 2019a). Its safety and reliability are critical to the regular operation of the ship (Bayer et al. 2018; Cheliotis & Lazakis, 2018; Lazakis et al. 2016). However, performance decay may occur to the propulsion system due to the high humidity and high salt characteristics of the marine environment (Fang et al. 2018; Kang et al. 2019; Wang et al. 2019). The decay modes can be divided into single decay and simultaneous decay. Single decay indicates a simple decay mode that only one kind of decay occurs at a time, and simultaneous decay indicates a complex decay mode that multiple decays occur at the same time. To improve the safety and reliability of the marine propulsion system, researchers have proposed many related approaches from the perspective of fault diagnosis.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48523429","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}
The unsteady propeller forces of an underwater vehicle were numerically simulated using computational fluid dynamics to investigate the effects of the axial location of the stern planes. A benchmark study was undertaken using a three-bladed propeller; experimental results of the nominal inflow wake profile were analyzed and the unsteady propeller forces were measured. The numerical method was applied to predict the unsteady propeller forces in the SUBOFF model’s wake by varying the axial locations of the stern planes. Several remarks were made on the primary harmonics of the hull’s wakes and blade-rate propeller forces. The hydroacoustic noise, which matches multiples of the number of propeller blades and its rotational speed, known as “blade-rate (BR) noise,” has been increasingly used to manage hydroacoustics for naval vessels. BR noise can be caused by alternating blade loads owing to fluctuations in the angle of attack of the blades because marine propellers are operated in the nonuniform wake of ships’ hulls. The unsteady blade load produces unsteady propeller forces that are transmitted via the propeller shaft and bearing, thus producing undesirable vibration and noise. Although the resultant BR noise is a common issue for marine vessels, in particular, submarines and other underwater vehicles deployed for undersea defense systems and oceanographic survey systems require strict specifications for the acoustic signature. Therefore, the unsteady propeller forces must be improved for reduced detectability, because the vehicles should be able to operate without being discovered while sonar detection technology continues to improve.
{"title":"Numerical Study on Multiple-Blade-Rate Unsteady Propeller Forces for Underwater Vehicles","authors":"Kenshiro Takahashi, J. Arai, T. Mori","doi":"10.5957/josr.08200048","DOIUrl":"https://doi.org/10.5957/josr.08200048","url":null,"abstract":"The unsteady propeller forces of an underwater vehicle were numerically simulated using computational fluid dynamics to investigate the effects of the axial location of the stern planes. A benchmark study was undertaken using a three-bladed propeller; experimental results of the nominal inflow wake profile were analyzed and the unsteady propeller forces were measured. The numerical method was applied to predict the unsteady propeller forces in the SUBOFF model’s wake by varying the axial locations of the stern planes. Several remarks were made on the primary harmonics of the hull’s wakes and blade-rate propeller forces.\u0000 \u0000 \u0000 The hydroacoustic noise, which matches multiples of the number of propeller blades and its rotational speed, known as “blade-rate (BR) noise,” has been increasingly used to manage hydroacoustics for naval vessels. BR noise can be caused by alternating blade loads owing to fluctuations in the angle of attack of the blades because marine propellers are operated in the nonuniform wake of ships’ hulls. The unsteady blade load produces unsteady propeller forces that are transmitted via the propeller shaft and bearing, thus producing undesirable vibration and noise. Although the resultant BR noise is a common issue for marine vessels, in particular, submarines and other underwater vehicles deployed for undersea defense systems and oceanographic survey systems require strict specifications for the acoustic signature. Therefore, the unsteady propeller forces must be improved for reduced detectability, because the vehicles should be able to operate without being discovered while sonar detection technology continues to improve.\u0000","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47337647","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}
J. Kao, S. Chin, F. Chang, Yu-Han Tsai, Hua Wu, Huan-Jia Xu
The objective of this paper is to predict the noise radiated from submarine propellers with different control surface types (the cross- and X-type). When the propellers are free from cavitation, such as those of submarines at a diving depth, the radiated noise dominate, due to unsteady propeller forces. A well-known submarine model (DARPA SUBOFF) is taken as the computing sample. Simulations for hydrodynamics, including stern wakes and unsteady propeller forces, are carried out by using CFD (Computational Fluid Dynamics) technology, and the results are compared with the experimental data. The accuracy of the predicted noise depends on the CFD results. Comparisons between the CFD results and the experimental data are in good agreement. The CFD results are treated as dipole strengths in the linear wave theory to predict the radiated noise caused by the unsteady forces of the propeller. It is found that, when the control surface is of the X-type, the propeller inflow is more uniform, and the radiated noise can be decreased by about 5 dB compared to the cruciform control surface. When submarines are at diving depth, the noise generated by unsteady propeller forces (i.e., dipole strengths) will dominate. Because the juncture vortex caused by the sail makes the propeller inflow more nonuniform, the dipole strength will be enhanced and the radiated noise will be more noticeable. The uniformity of the wake field at the stern should be controlled well in order to restrain the radiated noise.
{"title":"Predicting the Radiated Noise of a Submarine Propeller with Different Types of Control Surfaces","authors":"J. Kao, S. Chin, F. Chang, Yu-Han Tsai, Hua Wu, Huan-Jia Xu","doi":"10.5957/josr.07190038","DOIUrl":"https://doi.org/10.5957/josr.07190038","url":null,"abstract":"The objective of this paper is to predict the noise radiated from submarine propellers with different control surface types (the cross- and X-type). When the propellers are free from cavitation, such as those of submarines at a diving depth, the radiated noise dominate, due to unsteady propeller forces. A well-known submarine model (DARPA SUBOFF) is taken as the computing sample. Simulations for hydrodynamics, including stern wakes and unsteady propeller forces, are carried out by using CFD (Computational Fluid Dynamics) technology, and the results are compared with the experimental data. The accuracy of the predicted noise depends on the CFD results. Comparisons between the CFD results and the experimental data are in good agreement. The CFD results are treated as dipole strengths in the linear wave theory to predict the radiated noise caused by the unsteady forces of the propeller. It is found that, when the control surface is of the X-type, the propeller inflow is more uniform, and the radiated noise can be decreased by about 5 dB compared to the cruciform control surface.\u0000 \u0000 \u0000 When submarines are at diving depth, the noise generated by unsteady propeller forces (i.e., dipole strengths) will dominate. Because the juncture vortex caused by the sail makes the propeller inflow more nonuniform, the dipole strength will be enhanced and the radiated noise will be more noticeable. The uniformity of the wake field at the stern should be controlled well in order to restrain the radiated noise.\u0000","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43591213","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}
Offshore structures floating at sea should use their dynamic positioning (DP) system to maintain position and heading against environmental loads, including wave loads, current loads, and wind loads. It is difficult to calculate environmental loads accurately and quickly, especially for wind loads due to the shielding effect of different parts on offshore structures. To improve the accuracy of wind load calculation, a new method considering shielding effect is proposed. With the new method, calculated wind force becomes much closer to wind tunnel test than the traditional method. As input data of DP capacity analysis, the environmental loads have critical impact on the design of DP system. A static method and a time-domain simulation method of DP capacity are also proposed, and a case study of drillship is carried out. The results of both static analysis and time-domain simulation of DP capacity show that the new wind load calculation method has improved the accuracy of environmental load calculation and DP capacity analysis. As the offshore oil and gas exploitation is going further into deep sea, offshore structures are to be used in harsh marine environments, including strong wind, current, and waves. Especially for wind, it can make great effect on the dynamic positioning (DP) system of offshore structures, which is designed to maintain position and heading. Once the DP system is not able to keep the offshore structures’ position and heading, it will cause an accident such as oil leakage and oil pollution in the ocean. Because of the wind shielding effect among all parts on offshore structures, such as deckhouse, derricks, cranes, pipe racks, the wind load is difficult to calculate accurately and quickly.
{"title":"Study on Dynamic Positioning Capacity Analysis Method Considering Wind Shielding Effect of Offshore Structure","authors":"Jinhui He, Haibin Zhang, R. Zhu","doi":"10.5957/josr.12200062","DOIUrl":"https://doi.org/10.5957/josr.12200062","url":null,"abstract":"Offshore structures floating at sea should use their dynamic positioning (DP) system to maintain position and heading against environmental loads, including wave loads, current loads, and wind loads. It is difficult to calculate environmental loads accurately and quickly, especially for wind loads due to the shielding effect of different parts on offshore structures. To improve the accuracy of wind load calculation, a new method considering shielding effect is proposed. With the new method, calculated wind force becomes much closer to wind tunnel test than the traditional method. As input data of DP capacity analysis, the environmental loads have critical impact on the design of DP system. A static method and a time-domain simulation method of DP capacity are also proposed, and a case study of drillship is carried out. The results of both static analysis and time-domain simulation of DP capacity show that the new wind load calculation method has improved the accuracy of environmental load calculation and DP capacity analysis.\u0000 \u0000 \u0000 As the offshore oil and gas exploitation is going further into deep sea, offshore structures are to be used in harsh marine environments, including strong wind, current, and waves. Especially for wind, it can make great effect on the dynamic positioning (DP) system of offshore structures, which is designed to maintain position and heading. Once the DP system is not able to keep the offshore structures’ position and heading, it will cause an accident such as oil leakage and oil pollution in the ocean. Because of the wind shielding effect among all parts on offshore structures, such as deckhouse, derricks, cranes, pipe racks, the wind load is difficult to calculate accurately and quickly.\u0000","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42208757","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}
Machine learning algorithms, namely artificial neural network modeling, were used to create prediction models for force and moment coefficients of axisymmetric bodies of revolution. These prediction models had highly nonlinear functional relationships to both geometric parameters and inflow conditions, totaling five input factors. A uniform experimental design was created consisting of 50 design points in these five factors and dictated which test points to simulate. Data was generated using computational fluid dynamic simulations, which were performed on all geometries using NavyFOAM at the experimental conditions prescribed by the designed experiment. The prediction models were validated by comparing behavioral trends in responses to previous research conducted by the author on a similar geometry. A test data sets was also created and used to ensure that the prediction models were not overfit to the training data and that they could accurately predict arbitrary geometries and inflow conditions within the experimental design region. Once the prediction models were validated, they were used to study the effects of varying the geometric parameters, inherent to the experiment, on each of the force and moment coefficients. Multidisciplinary optimization (MDO) schemes used in the early concept design phases for aero/hydrodynamic vehicles often use simplified planar maneuvering characteristics based on empirical or analytical relations in order to limit the computational cost of maneuverability prediction. This method leaves a more detailed analysis of the maneuvering behavior of a design to later in the process, where improvement or correction of an adverse behavior may be difficult to implement. The analysis of out-of-plane conditions or combined pitch-yaw conditions especially, are usually relegated to the detail analysis phase as empirical/ analytical descriptions of these conditions are lacking in the literature. It is therefore desired to develop a method to move these more detailed maneuvering analyses forward in the design phase.
{"title":"Hydrodynamic Characterization of Bodies of Revolution through Statistical-Empirical Prediction Modeling Using Machine Learning","authors":"C. Thurman, J. R. Somero","doi":"10.5957/josr.06200035","DOIUrl":"https://doi.org/10.5957/josr.06200035","url":null,"abstract":"Machine learning algorithms, namely artificial neural network modeling, were used to create prediction models for force and moment coefficients of axisymmetric bodies of revolution. These prediction models had highly nonlinear functional relationships to both geometric parameters and inflow conditions, totaling five input factors. A uniform experimental design was created consisting of 50 design points in these five factors and dictated which test points to simulate. Data was generated using computational fluid dynamic simulations, which were performed on all geometries using NavyFOAM at the experimental conditions prescribed by the designed experiment. The prediction models were validated by comparing behavioral trends in responses to previous research conducted by the author on a similar geometry. A test data sets was also created and used to ensure that the prediction models were not overfit to the training data and that they could accurately predict arbitrary geometries and inflow conditions within the experimental design region. Once the prediction models were validated, they were used to study the effects of varying the geometric parameters, inherent to the experiment, on each of the force and moment coefficients.\u0000 \u0000 \u0000 Multidisciplinary optimization (MDO) schemes used in the early concept design phases for aero/hydrodynamic vehicles often use simplified planar maneuvering characteristics based on empirical or analytical relations in order to limit the computational cost of maneuverability prediction. This method leaves a more detailed analysis of the maneuvering behavior of a design to later in the process, where improvement or correction of an adverse behavior may be difficult to implement. The analysis of out-of-plane conditions or combined pitch-yaw conditions especially, are usually relegated to the detail analysis phase as empirical/ analytical descriptions of these conditions are lacking in the literature. It is therefore desired to develop a method to move these more detailed maneuvering analyses forward in the design phase.\u0000","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41815340","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}
Yibin Deng, Xiaogang Yang, Shi-dong Fan, Hao Jin, Tao Su, Han-hua Zhu
Because of the long propulsion shafting of special ships, the number of bearings is large and the number of measured bearing reaction data is small, which makes the installation of shafting difficult. To apply a small amount of measured data to the process of ship installation so as to accurately calculate the displacement value in the actual installation, this article proposes a method to calculate the displacement value of shafting intermediate bearing based on different confidence-level training samples. Taking a ro-ro ship as the research object, this research simulates the actual installation process, gives a higher confidence level to a small amount of measured data, constructs a new training sample set for machine learning, and finally obtains the genetic algorithm-backpropagation(GABP) neural network reflecting the actual installation process. At the same time, this research compares the accuracy between different confidence-level training sample shafting neural network and the shafting neural network without measured data, and the results show that the accuracy of shafting neural network with different confidence-level training samples is higher. Although as the adjustment times and the number of measured data increase, the network accuracy is significantly improved. After adding four measured data, the maximum error is within 1%, which can play a guiding role in the ship propulsion shafting alignment. With the rapid development of science and technology in the world, special ships such as engineering ships, official ships, and warships play an important role (Carrasco et al. 2020; Prill et al. 2020). Some ships of this special type are limited by various factors such as the stern line of engine room, hull stability, and operation requirements. They usually adopt the layout of middle or front engine room, which causes the propulsion system to have a longer shaft and the number of intermediate shafts and intermediate bearings exceeds two. This forms a so-called multisupport shafting (Lee et al. 2019) and it increases the difficulty of shafting alignment because of the force-coupling between the bearings (Lai et al. 2018a, 2018b). The process of the existing methods for calculating the displacement value is complex, and because of the influence of installation error and other factors, it is necessary to adjust the bearing height several times to make the bearing reaction meet the specification requirements(Kim et al. 2017, Ko et al. 2017). So how to predict the accurate displacement value of each intermediate bearing is the key to solving the problem of multisupport shafting intermediate bearing installation and calibration (Zhou et al. 2005, Xiao-fei et al. 2017).
由于特种船舶的推进轴系较长，轴承数量较多，而测量到的轴承反力数据较少，给轴系的安装带来了困难。为了将少量的实测数据应用到船舶安装过程中，以便准确计算实际安装中的位移值，本文提出了一种基于不同置信度训练样本的轴系中间轴承位移值计算方法。本研究以一艘滚装船为研究对象，模拟实际安装过程，对少量实测数据给予较高的置信度，构建新的训练样本集进行机器学习，最终得到反映实际安装过程的遗传算法-反向传播(GABP)神经网络。同时，本研究比较了不同置信水平训练样本的轴系神经网络与不含实测数据的轴系神经网络的精度，结果表明，不同置信水平训练样本的轴系神经网络精度更高。虽然随着平差次数和测量数据数量的增加，网络精度得到了显著提高。添加4个实测数据后，最大误差在1%以内，可对船舶推进轴系校中起到指导作用。随着世界科学技术的飞速发展，工程船、公务船、军舰等特种船舶发挥着重要作用(Carrasco et al. 2020;Prill et al. 2020)。这种特殊类型的一些船舶受到诸如机舱尾线、船体稳定性和操作要求等各种因素的限制。它们通常采用中机舱或前机舱的布置，这使得推进系统具有较长的轴，中间轴和中间轴承的数量超过两个。这形成了所谓的多支撑轴系(Lee et al. 2019)，由于轴承之间的力耦合，它增加了轴系对准的难度(Lai et al. 2018a, 2018b)。现有的位移值计算方法过程复杂，由于安装误差等因素的影响，需要多次调整轴承高度，使轴承反力满足规范要求(Kim et al. 2017, Ko et al. 2017)。因此，如何准确预测各中间轴承的位移值是解决多支承轴系中间轴承安装标定问题的关键(Zhou et al. 2005, xiaofei et al. 2017)。
{"title":"Research on the Installation and Alignment Method of Ship Multi-support Bearings Based on Different Confidence-Level Training Samples","authors":"Yibin Deng, Xiaogang Yang, Shi-dong Fan, Hao Jin, Tao Su, Han-hua Zhu","doi":"10.5957/josr.11200056","DOIUrl":"https://doi.org/10.5957/josr.11200056","url":null,"abstract":"Because of the long propulsion shafting of special ships, the number of bearings is large and the number of measured bearing reaction data is small, which makes the installation of shafting difficult. To apply a small amount of measured data to the process of ship installation so as to accurately calculate the displacement value in the actual installation, this article proposes a method to calculate the displacement value of shafting intermediate bearing based on different confidence-level training samples. Taking a ro-ro ship as the research object, this research simulates the actual installation process, gives a higher confidence level to a small amount of measured data, constructs a new training sample set for machine learning, and finally obtains the genetic algorithm-backpropagation(GABP) neural network reflecting the actual installation process. At the same time, this research compares the accuracy between different confidence-level training sample shafting neural network and the shafting neural network without measured data, and the results show that the accuracy of shafting neural network with different confidence-level training samples is higher. Although as the adjustment times and the number of measured data increase, the network accuracy is significantly improved. After adding four measured data, the maximum error is within 1%, which can play a guiding role in the ship propulsion shafting alignment.\u0000 \u0000 \u0000 With the rapid development of science and technology in the world, special ships such as engineering ships, official ships, and warships play an important role (Carrasco et al. 2020; Prill et al. 2020). Some ships of this special type are limited by various factors such as the stern line of engine room, hull stability, and operation requirements. They usually adopt the layout of middle or front engine room, which causes the propulsion system to have a longer shaft and the number of intermediate shafts and intermediate bearings exceeds two. This forms a so-called multisupport shafting (Lee et al. 2019) and it increases the difficulty of shafting alignment because of the force-coupling between the bearings (Lai et al. 2018a, 2018b). The process of the existing methods for calculating the displacement value is complex, and because of the influence of installation error and other factors, it is necessary to adjust the bearing height several times to make the bearing reaction meet the specification requirements(Kim et al. 2017, Ko et al. 2017). So how to predict the accurate displacement value of each intermediate bearing is the key to solving the problem of multisupport shafting intermediate bearing installation and calibration (Zhou et al. 2005, Xiao-fei et al. 2017).\u0000","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46588391","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：