A complete approach for wall-modeled large-eddy simulation (WMLES) is demonstrated for the simulation of the flow around a bulk carrier in the model scale. Essential components of the method are an a-priori estimate of the thickness of the turbulent boundary layer (TBL) over the hull and to use an unstructured grid with the appropriate resolution relative to this thickness. Expressions from the literature for the scaling of the computational cost, in terms of the grid size, with Reynolds number, are adapted in this application. It is shown that WMLES is possible for model scale ship hydrodynamics, with ∼108 grid cells, which is a gain of at least one order of magnitude as compared with wall-resolving LES. For the canonical case of a flat-plate TBL, the effects of wall model parameters and grid cell topology on the predictive accuracy of the method are investigated. For the flat-plate case, WMLES results are compared with results from direct numerical simulation, RANS (Reynolds-averaged Navier-Stokes), and semi-empirical formulas. For the bulk carrier flow, WMLES and RANS are compared, but further validation is needed to assess the predictive accuracy of the approach.
{"title":"Wall-Modeled LES for Ship Hydrodynamics in Model Scale","authors":"M. Liefvendahl, Mattias Johansson","doi":"10.5957/JOSR.09180065","DOIUrl":"https://doi.org/10.5957/JOSR.09180065","url":null,"abstract":"A complete approach for wall-modeled large-eddy simulation (WMLES) is demonstrated for the simulation of the flow around a bulk carrier in the model scale. Essential components of the method are an a-priori estimate of the thickness of the turbulent boundary layer (TBL) over the hull and to use an unstructured grid with the appropriate resolution relative to this thickness. Expressions from the literature for the scaling of the computational cost, in terms of the grid size, with Reynolds number, are adapted in this application. It is shown that WMLES is possible for model scale ship hydrodynamics, with ∼108 grid cells, which is a gain of at least one order of magnitude as compared with wall-resolving LES. For the canonical case of a flat-plate TBL, the effects of wall model parameters and grid cell topology on the predictive accuracy of the method are investigated. For the flat-plate case, WMLES results are compared with results from direct numerical simulation, RANS (Reynolds-averaged Navier-Stokes), and semi-empirical formulas. For the bulk carrier flow, WMLES and RANS are compared, but further validation is needed to assess the predictive accuracy of the approach.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":" ","pages":"1-14"},"PeriodicalIF":1.4,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46552904","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}
Potential flow-based methods are common in early design stages because of their associated speed and relative simplicity. By separating the resistance components of a ship into viscous and wave resistance, an inviscid method such as potential flow can be used for wave resistance determination. However, gravity waves are affected by viscosity and decay with time and distance. It has, therefore, long been assumed that the inclusion of a damping parameter in potential flow would better model the wave resistance. This article presents a Kelvin-Neumann dissipative potential flow model. A Rayleigh damping term is inserted into the Navier-Stokes equations to capture the decay of waves. A new 3D Green’s function based on the Havelock-Lunde formulation is derived by the use of a Fourier transform. An upper limit for the Rayleigh damping term is found by comparison with experiments and a possible improvement on conventional potential flow models for the wave making resistance prediction of a submerged ellipsoid is proposed.
{"title":"A Dissipative Green’s Function Approach to Modeling Gravity Waves behind Submerged Bodies","authors":"M. Fürth, M. Tan, Zhimin Chen, M. Arai","doi":"10.5957/JOSR.08170054","DOIUrl":"https://doi.org/10.5957/JOSR.08170054","url":null,"abstract":"Potential flow-based methods are common in early design stages because of their associated speed and relative simplicity. By separating the resistance components of a ship into viscous and wave resistance, an inviscid method such as potential flow can be used for wave resistance determination. However, gravity waves are affected by viscosity and decay with time and distance. It has, therefore, long been assumed that the inclusion of a damping parameter in potential flow would better model the wave resistance. This article presents a Kelvin-Neumann dissipative potential flow model. A Rayleigh damping term is inserted into the Navier-Stokes equations to capture the decay of waves. A new 3D Green’s function based on the Havelock-Lunde formulation is derived by the use of a Fourier transform. An upper limit for the Rayleigh damping term is found by comparison with experiments and a possible improvement on conventional potential flow models for the wave making resistance prediction of a submerged ellipsoid is proposed.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":"65 1","pages":"72-85"},"PeriodicalIF":1.4,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45056618","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 shipping business expects to develop energy-saving and drag-reducing techniques addressing the cost of shipping and environmental problems. It has been reported that for slow-moving vessels, frictional resistance accounts for up to 80% of the total resistance, needing urgent attention to reduce the same. To reduce frictional resistance, the air has been used as lubricant, which is injected below the moving body known as Bubble Drag Reduction or the Air Lubrication System. In this article, results obtained from experimental investigations into drag reduction of a 1:23 scaled model of an 8000-ton deadweight bulk carrier by injecting air bubbles below it are presented. Investigations were carried out for a speed range of 6-10 knots, and for each speed, the effect of six injection flow rates of .5-3.0 CFM were investigated. To investigate the effect of different sizes of injection holes, two types of injector units have been used: one with injection holes of 1 mm diameter and the other with injection holes of 2 mm diameter. The study carried out has many practical implications because it is easier to create bigger size holes which will reduce the power required to inject air, thereby increasing the efficiency of the entire technique. 1. Introduction It is projected that crude oil prices will continue to increase in the future, forcing marine businesses to rely on researchers to develop energy-saving devices (ESD) and drag-reducing technologies. It has been reported that for slow-moving vessels such tankers, bulk carriers, very large crude carrier (VLCC), and ultra large crude carrier (ULCC), frictional resistance accounts for up to 80% of the total resistance, needing urgent attention to reduce the same (Lewis n.d.; Larsson & Raven 2010). Numerous technologies have been studied and applied in reducing the frictional drag (Brostow 2008; Abdulbari et al. 2013; Luo et al. 2015; Mohammad & Mousavi 2015; Sindagi et al. 2016). Based on further studies Sindagi et al. (2018a, 2018b, 2018c, 2018d) and Sindagi and Vijayakumar (2020), it is concluded that air lubrication has additional advantages over other technologies, such as it is environmentally friendly, the operation is quite easy, and it results in low operating costs and high energy savings. Moreover, with air lubrication, an 80% reduction in the drag of the flat plate was achieved by Merkle et al. (1983) and Madavan et al. (1984, 1985).
{"title":"Experimental Parametric Investigation to Reduce Drag of a Scaled Model of Bulk Carrier Using BDR/ALS Technique","authors":"S. Sindagi, R. Vijayakumar, B. K. Saxena","doi":"10.5957/JOSR.02190009","DOIUrl":"https://doi.org/10.5957/JOSR.02190009","url":null,"abstract":"The shipping business expects to develop energy-saving and drag-reducing techniques addressing the cost of shipping and environmental problems. It has been reported that for slow-moving vessels, frictional resistance accounts for up to 80% of the total resistance, needing urgent attention to reduce the same. To reduce frictional resistance, the air has been used as lubricant, which is injected below the moving body known as Bubble Drag Reduction or the Air Lubrication System. In this article, results obtained from experimental investigations into drag reduction of a 1:23 scaled model of an 8000-ton deadweight bulk carrier by injecting air bubbles below it are presented. Investigations were carried out for a speed range of 6-10 knots, and for each speed, the effect of six injection flow rates of .5-3.0 CFM were investigated. To investigate the effect of different sizes of injection holes, two types of injector units have been used: one with injection holes of 1 mm diameter and the other with injection holes of 2 mm diameter. The study carried out has many practical implications because it is easier to create bigger size holes which will reduce the power required to inject air, thereby increasing the efficiency of the entire technique.\u0000 1. Introduction\u0000 It is projected that crude oil prices will continue to increase in the future, forcing marine businesses to rely on researchers to develop energy-saving devices (ESD) and drag-reducing technologies. It has been reported that for slow-moving vessels such tankers, bulk carriers, very large crude carrier (VLCC), and ultra large crude carrier (ULCC), frictional resistance accounts for up to 80% of the total resistance, needing urgent attention to reduce the same (Lewis n.d.; Larsson & Raven 2010). Numerous technologies have been studied and applied in reducing the frictional drag (Brostow 2008; Abdulbari et al. 2013; Luo et al. 2015; Mohammad & Mousavi 2015; Sindagi et al. 2016). Based on further studies Sindagi et al. (2018a, 2018b, 2018c, 2018d) and Sindagi and Vijayakumar (2020), it is concluded that air lubrication has additional advantages over other technologies, such as it is environmentally friendly, the operation is quite easy, and it results in low operating costs and high energy savings. Moreover, with air lubrication, an 80% reduction in the drag of the flat plate was achieved by Merkle et al. (1983) and Madavan et al. (1984, 1985).","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":"1 1","pages":"1-9"},"PeriodicalIF":1.4,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49255993","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}
Fatigue strength assessment of a butt-welded joint in ship structures based on a time-domain strain approach is performed in this study. The service life load histories applied to the butt-welded joint located on the deck of a bulk carrier are generated, accounting for the still-water and wave-induced loads. The rainflow counting method is applied to analyze the load histories, and the long-term distributions of the load range are compared with those based on the conventional spectral fatigue analysis. An approach of converting the load history to a series of closed notch stress-strain hysteresis loops and several open notch stress-strain hysteresis curves is proposed and demonstrated under variable amplitude loading. The approach is based on analytical notch stress-strain estimations and consists of several steps to consider the material memory effect, overcoming some limitations of the existing methods. To determine the fatigue damage for the variable amplitude loading, a design fatigue curve is derived considering the uncertainty in the fatigue lives and load sequence effects. The intrinsic fatigue limit concept is used to filter the small amplitude cycles that do not have a damaging effect. The fatigue strength of the butt-welded joint is analyzed, taking the weld-induced residual stress and misalignment effects into account explicitly. The notch mean stresses or strain amplitudes of the cycles are significantly enhanced because of the presence of a high level of weld-induced tensile residual stress or misalignment, resulting in highly severe fatigue damage. 1. Introduction Complex ship structures containing geometrical and material discontinuities are prone to fatigue because of cyclic loads. Therefore, fatigue strength assessment has been an important criterion in the ship structural design (Guedes Soares & Moan 1991). Various fatigue design concepts for the assessment of welded joints, where fatigue failures mostly originate, are applied (Xu 1997; Radaj et al. 2006), and they can be classified into two types. The first one is based on S-N curves in combination with the Palmgren-Miner rule, and the second one is based on the crack propagation models and failure criteria.
基于时域应变法对舰船结构对接焊接接头进行了疲劳强度评估。建立了散货船甲板对接接头的使用寿命载荷历史，计算了静水载荷和波浪载荷。采用雨流计数法对载荷历史进行了分析，并与传统的频谱疲劳分析结果进行了比较。提出了一种将载荷历史转换为一系列闭合缺口应力-应变滞回曲线和若干开缺口应力-应变滞回曲线的方法，并对变幅加载进行了验证。该方法基于缺口应力-应变的分析估计，并考虑了材料记忆效应，克服了现有方法的一些局限性。为了确定变幅加载下的疲劳损伤，考虑了疲劳寿命和加载顺序效应的不确定性，导出了设计疲劳曲线。本征疲劳极限的概念是用来过滤小振幅循环，不具有破坏性的影响。对对接接头的疲劳强度进行了分析，明确考虑了焊接残余应力和错向效应。由于存在高水平的焊接引起的拉伸残余应力或错位，导致高度严重的疲劳损伤，因此循环的缺口平均应力或应变幅值显着增强。1. 包含几何和材料不连续的复杂船舶结构在循环荷载作用下容易产生疲劳。因此，疲劳强度评估已成为船舶结构设计的重要标准(Guedes Soares & Moan 1991)。焊接接头是疲劳失效的主要来源，应用了各种疲劳设计概念来评估焊接接头(Xu 1997;Radaj et al. 2006)，它们可以分为两种类型。第一种是基于S-N曲线并结合Palmgren-Miner规则，第二种是基于裂纹扩展模型和破坏准则。
{"title":"Fatigue Strength Assessment of a Butt-Welded Joint in Ship Structures Based on Time-Domain Strain Approach","authors":"Y. Dong, Y. Garbatov, C. Soares","doi":"10.5957/JOSR.04180019","DOIUrl":"https://doi.org/10.5957/JOSR.04180019","url":null,"abstract":"Fatigue strength assessment of a butt-welded joint in ship structures based on a time-domain strain approach is performed in this study. The service life load histories applied to the butt-welded joint located on the deck of a bulk carrier are generated, accounting for the still-water and wave-induced loads. The rainflow counting method is applied to analyze the load histories, and the long-term distributions of the load range are compared with those based on the conventional spectral fatigue analysis. An approach of converting the load history to a series of closed notch stress-strain hysteresis loops and several open notch stress-strain hysteresis curves is proposed and demonstrated under variable amplitude loading. The approach is based on analytical notch stress-strain estimations and consists of several steps to consider the material memory effect, overcoming some limitations of the existing methods. To determine the fatigue damage for the variable amplitude loading, a design fatigue curve is derived considering the uncertainty in the fatigue lives and load sequence effects. The intrinsic fatigue limit concept is used to filter the small amplitude cycles that do not have a damaging effect. The fatigue strength of the butt-welded joint is analyzed, taking the weld-induced residual stress and misalignment effects into account explicitly. The notch mean stresses or strain amplitudes of the cycles are significantly enhanced because of the presence of a high level of weld-induced tensile residual stress or misalignment, resulting in highly severe fatigue damage.\u0000 1. Introduction\u0000 Complex ship structures containing geometrical and material discontinuities are prone to fatigue because of cyclic loads. Therefore, fatigue strength assessment has been an important criterion in the ship structural design (Guedes Soares & Moan 1991). Various fatigue design concepts for the assessment of welded joints, where fatigue failures mostly originate, are applied (Xu 1997; Radaj et al. 2006), and they can be classified into two types. The first one is based on S-N curves in combination with the Palmgren-Miner rule, and the second one is based on the crack propagation models and failure criteria.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":"1 1","pages":"1-16"},"PeriodicalIF":1.4,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46060208","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}
Modeling and simulation continues to be an important tool for determining the response of sea-going vessels to wind and waves. To provide appropriate forcing functions to the models, it is important to have environmental data of sufficient fidelity to facilitate an assessment of platform response, which is as accurate as possible within the practical constraints of time and resources. Fortunately, there are a variety of sources of good wave data, including the U.S. National Oceanic and Atmospheric Administration. This study examines the wave data in the context of simulation codes for assessing characteristics of ocean craft response. It also looks at some practical considerations to limit the scope of simulations. The work is strongly influenced by modeling and simulation of naval surface ships, looking for extreme behaviors, but many of the issues discussed are broadly applicable to other applications. Copyright 2021 Her Majesty the Queen in Right of Canada, Department of National Defence
{"title":"Probability of Sea Condition for Ship Strength, Stability, and Motion Studies","authors":"D. Perrault","doi":"10.5957/JOSR.05190024","DOIUrl":"https://doi.org/10.5957/JOSR.05190024","url":null,"abstract":"Modeling and simulation continues to be an important tool for determining the response of sea-going vessels to wind and waves. To provide appropriate forcing functions to the models, it is important to have environmental data of sufficient fidelity to facilitate an assessment of platform response, which is as accurate as possible within the practical constraints of time and resources. Fortunately, there are a variety of sources of good wave data, including the U.S. National Oceanic and Atmospheric Administration. This study examines the wave data in the context of simulation codes for assessing characteristics of ocean craft response. It also looks at some practical considerations to limit the scope of simulations. The work is strongly influenced by modeling and simulation of naval surface ships, looking for extreme behaviors, but many of the issues discussed are broadly applicable to other applications.\u0000 Copyright 2021 Her Majesty the Queen in Right of Canada, Department of National Defence","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":"65 1","pages":"1-14"},"PeriodicalIF":1.4,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43398826","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}
Depending on model sizes and test speeds, model Reynolds numbers are typically one to two orders of magnitude less than those occurring at full scale. The region of laminar flow is significantly larger on a model surface than at full scale. Turbulence stimulators (TSs) are extensively applied in model resistance tests to simulate ship boundary layer flow. Because of lack of theoretical guidance, the size, shape, and location of turbulent stimulators used in each test facility are typically selected based on experience gained in each laboratory, and parasitic drag induced by TSs is subtracted from measured model resistance in some test facilities and not subtracted in other facilities. If turbulence stimulation can be specified in such a way as to achieve momentum thickness similarity between the model and full scale, the form factor will be constant, so a simple scaling formula can be applied to predict ship resistance. Ship resistance can be predicted from measured model resistance with the application of this simple scaling formula. The article describes how for a given body geometry, ship Reynolds number and model Reynolds number, a unique TS (size, shape, and location) can be designed based on three equations derived in this article. This uniquely designed TS is termed the "resistance similitude simulator" in this article. The parasitic drag induced by the simulator is a part of the similarity solution and does not need to be subtracted from measured model resistance. 1. Introduction The ability to predict resistance plays an important role in the design of a ship or submarine. An accurate prediction of the drag of the vessel is required for the propulsor design and to determine the required power. The resistance of the vessel also strongly influences its lifetime operation costs. Although computational methods are now commonly used to estimate ship resistance, model tests are still heavily relied on, and scaling formulae are used to relate model data to full-scale performance.
{"title":"Ship Hull Resistance Prediction from Model Tests with a Resistance Similitude Simulator","authors":"Young T. Shen, M. Hughes","doi":"10.5957/JOSR.08190051","DOIUrl":"https://doi.org/10.5957/JOSR.08190051","url":null,"abstract":"Depending on model sizes and test speeds, model Reynolds numbers are typically one to two orders of magnitude less than those occurring at full scale. The region of laminar flow is significantly larger on a model surface than at full scale. Turbulence stimulators (TSs) are extensively applied in model resistance tests to simulate ship boundary layer flow. Because of lack of theoretical guidance, the size, shape, and location of turbulent stimulators used in each test facility are typically selected based on experience gained in each laboratory, and parasitic drag induced by TSs is subtracted from measured model resistance in some test facilities and not subtracted in other facilities. If turbulence stimulation can be specified in such a way as to achieve momentum thickness similarity between the model and full scale, the form factor will be constant, so a simple scaling formula can be applied to predict ship resistance. Ship resistance can be predicted from measured model resistance with the application of this simple scaling formula. The article describes how for a given body geometry, ship Reynolds number and model Reynolds number, a unique TS (size, shape, and location) can be designed based on three equations derived in this article. This uniquely designed TS is termed the \"resistance similitude simulator\" in this article. The parasitic drag induced by the simulator is a part of the similarity solution and does not need to be subtracted from measured model resistance.\u0000 1. Introduction\u0000 The ability to predict resistance plays an important role in the design of a ship or submarine. An accurate prediction of the drag of the vessel is required for the propulsor design and to determine the required power. The resistance of the vessel also strongly influences its lifetime operation costs. Although computational methods are now commonly used to estimate ship resistance, model tests are still heavily relied on, and scaling formulae are used to relate model data to full-scale performance.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":"1 1","pages":"1-13"},"PeriodicalIF":1.4,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47675191","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}
N. Petacco, G. Vernengo, D. Villa, Antonio Coppedé, P. Gualeni
The sensitivity of ship stability performance in waves to geometric variation has been investigated by means of a simulation-based design framework. The study was devoted to assess the influence of hull geometry variations on some stability failure modes, namely, parametric roll (PR) and pure loss of stability (PLS). The application has been developed by using a representative model of a postpanamax container vessel. PR and PLS phenomena have been investigated by the application of second-generation intact stability criteria (SGISc). The initial multidimensional design space has been filled by 500 design configurations identified by means of a design of experiments approach. A method developed in-house, combining the subdivision surface and free-form deformation approaches, has been used to create the whole set of design alternatives. The generated design configurations have been assessed analyzing the results derived from application of the first- and the second-level SGIS vulnerability criteria for both the selected stability failure modes. To strengthen the correlation behaviors, the design space has then been further explored by using 10k design configurations exploiting the capabilities of a surrogate model-based approximation, relying on a Gaussian process formulation. The study has been focused on the correlations among the variables and the response functions, i.e., the outcomes of the SGIS vulnerability criteria. The significance, in terms of effects, of each geometry shape variable has been investigated. Results have been discussed in the light of the SGISc structure, to provide further insight into this innovative safety framework for a modern approach to intact stability. 1. Introduction In the last 10 years, the development of the so-called second-generation intact stability criteria (SGISc) has been one of the most engaging topics addressed by the Sub-Committee on Safety Design and Construction (SDC) of the International Maritime Organization (IMO).
{"title":"Influence of Systematic Hull Shape Variations on Ship Stability Performances in Waves","authors":"N. Petacco, G. Vernengo, D. Villa, Antonio Coppedé, P. Gualeni","doi":"10.5957/JOSR.12190076","DOIUrl":"https://doi.org/10.5957/JOSR.12190076","url":null,"abstract":"The sensitivity of ship stability performance in waves to geometric variation has been investigated by means of a simulation-based design framework. The study was devoted to assess the influence of hull geometry variations on some stability failure modes, namely, parametric roll (PR) and pure loss of stability (PLS). The application has been developed by using a representative model of a postpanamax container vessel. PR and PLS phenomena have been investigated by the application of second-generation intact stability criteria (SGISc). The initial multidimensional design space has been filled by 500 design configurations identified by means of a design of experiments approach. A method developed in-house, combining the subdivision surface and free-form deformation approaches, has been used to create the whole set of design alternatives. The generated design configurations have been assessed analyzing the results derived from application of the first- and the second-level SGIS vulnerability criteria for both the selected stability failure modes. To strengthen the correlation behaviors, the design space has then been further explored by using 10k design configurations exploiting the capabilities of a surrogate model-based approximation, relying on a Gaussian process formulation. The study has been focused on the correlations among the variables and the response functions, i.e., the outcomes of the SGIS vulnerability criteria. The significance, in terms of effects, of each geometry shape variable has been investigated. Results have been discussed in the light of the SGISc structure, to provide further insight into this innovative safety framework for a modern approach to intact stability.\u0000 1. Introduction\u0000 In the last 10 years, the development of the so-called second-generation intact stability criteria (SGISc) has been one of the most engaging topics addressed by the Sub-Committee on Safety Design and Construction (SDC) of the International Maritime Organization (IMO).","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":" ","pages":"1-14"},"PeriodicalIF":1.4,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44185223","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}
V. Serebryakov, V. Moroz, Viktor Kochin, J. Dzielski
This article presents experimental studies of the planing motion of an axisymmetric cylindrical body along the surface of a cavity formed behind an axisymmetric cavitator at some angle of attack. The main focus is on the analysis of processes of interaction between the planing body and cavity surfaces. It also develops methods for determining the forces and cavity shape in the interaction zone and behind the planing surface. A number of issues related to supercavitating motion at shallow depth are investigated for moderate Froude numbers under conditions of non-negligible gravity effect.
{"title":"Experimental Study on Planing Motion of a Cylinder at Angle of Attack in the Cavity Formed behind an Axisymmetric Cavitator","authors":"V. Serebryakov, V. Moroz, Viktor Kochin, J. Dzielski","doi":"10.5957/JOSR.09180077","DOIUrl":"https://doi.org/10.5957/JOSR.09180077","url":null,"abstract":"This article presents experimental studies of the planing motion of an axisymmetric cylindrical body along the surface of a cavity formed behind an axisymmetric cavitator at some angle of attack. The main focus is on the analysis of processes of interaction between the planing body and cavity surfaces. It also develops methods for determining the forces and cavity shape in the interaction zone and behind the planing surface. A number of issues related to supercavitating motion at shallow depth are investigated for moderate Froude numbers under conditions of non-negligible gravity effect.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2020-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46785093","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}
B. C. Peifer, Christopher Callahan-Dudley, Simo A. Mäkiharju
We examined the feasibility of combining a superhydrophobic surface (SHS) and air layer drag reduction (ALDR) to achieve the frictional drag reduction (DR) shown achievable with traditional ALDR, but at a reduced gas flux to increase the achievable net energy savings. The effect of a commercial SHS coating on the gas flux required to maintain a stable air layer (AL) for DR was investigated and compared with that of a painted non-SHS at Reynolds numbers up to 5.1 X 106. Quantitative electrical impedance measurements and more qualitative image analysis were used to characterize surface coverage and to determine whether a stable AL was formed and maintained over the length of the model. Analysis of video and still images for both the SHS and painted surface gives clear indications that the SHS is able to maintain AL consistency at significantly lower gas flux than required on the non-SHS painted surface. Hydrophobicity of the surfaces was characterized through droplet contact angle measurements, and roughness of all the flow surfaces was measured. The results from these preliminary experiments seem to indicate that for conditions explored (up to Rex = 5.1 X 106), there is a significant decrease in the amount of gas required to establish a uniform AL (and hence presumably achieve ALDR) on the SHS when compared with a hydraulically smooth painted non-SHS.
我们研究了将超疏水表面（SHS）和空气层减阻（ALDR）相结合以实现传统ALDR所显示的可实现的摩擦减阻（DR）的可行性，但在降低气体流量的情况下，以增加可实现的净节能。研究了商业SHS涂层对维持DR稳定空气层（AL）所需气体流量的影响，并将其与雷诺数高达5.1 X 106的喷涂非SHS涂层的气体流量进行了比较。使用定量电阻抗测量和更定性的图像分析来表征表面覆盖率，并确定在模型的整个长度上是否形成并保持稳定的AL。对SHS和涂漆表面的视频和静态图像的分析清楚地表明，SHS能够在比非SHS涂漆表面所需的气体流量低得多的情况下保持AL一致性。通过液滴接触角测量表征了表面的疏水性，并测量了所有流动表面的粗糙度。这些初步实验的结果似乎表明，对于所探索的条件（高达Rex=5.1 X 106），与液压光滑涂漆的非SHS相比，在SHS上建立均匀AL（因此可能实现ALDR）所需的气体量显著减少。
{"title":"Air Layer on Superhydrophobic Surface for Frictional Drag Reduction","authors":"B. C. Peifer, Christopher Callahan-Dudley, Simo A. Mäkiharju","doi":"10.5957/JOSR.09180074","DOIUrl":"https://doi.org/10.5957/JOSR.09180074","url":null,"abstract":"We examined the feasibility of combining a superhydrophobic surface (SHS) and air layer drag reduction (ALDR) to achieve the frictional drag reduction (DR) shown achievable with traditional ALDR, but at a reduced gas flux to increase the achievable net energy savings. The effect of a commercial SHS coating on the gas flux required to maintain a stable air layer (AL) for DR was investigated and compared with that of a painted non-SHS at Reynolds numbers up to 5.1 X 106. Quantitative electrical impedance measurements and more qualitative image analysis were used to characterize surface coverage and to determine whether a stable AL was formed and maintained over the length of the model. Analysis of video and still images for both the SHS and painted surface gives clear indications that the SHS is able to maintain AL consistency at significantly lower gas flux than required on the non-SHS painted surface. Hydrophobicity of the surfaces was characterized through droplet contact angle measurements, and roughness of all the flow surfaces was measured. The results from these preliminary experiments seem to indicate that for conditions explored (up to Rex = 5.1 X 106), there is a significant decrease in the amount of gas required to establish a uniform AL (and hence presumably achieve ALDR) on the SHS when compared with a hydraulically smooth painted non-SHS.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2020-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46986851","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}
This article introduces the composition and 12 operating conditions of a four-engine two-propeller hybrid power system. Through the combination of gearbox clutch and disconnection, the propulsion system has four single-engine operation modes, two double-engine parallel operation modes, and six PTI operation modes. Because the propulsion system has a variety of operating conditions, each operating condition has a form of energy transfer. As a result, its energy management and control are more complicated. To study the energy management and control strategy of a diesel- electric hybrid propulsion system, this work mainly studies the simulation model and sub-models of a diesel-electric hybrid propulsion system. In this study, MATLAB/ SIMULINK software is used to build the diesel engine model, motor model, and ship engine system mathematical model. The test and analysis were carried out on the test bench of the diesel-electric hybrid power system. By comparing the theoretical value of the SIMULINK simulation model with the test value of the test bench system, the correctness of each sub-model modeling method is verified. On the one hand, research on the text lays a theoretical foundation for the subsequent implementation of the conventional energy management and control strategy based on state identification on the unified management and distribution of the diesel-electric hybrid power system. At the same time, energy management of the diesel-electric hybrid system is also carried out. Optimization research provides theoretical guidance.
{"title":"Research on Simulation and Experiment of Ship Complex Diesel-Electric Hybrid Propulsion System","authors":"Nengqi Xiao, Xiang Xu, Baojia Chen","doi":"10.5957/JOSR.02190007","DOIUrl":"https://doi.org/10.5957/JOSR.02190007","url":null,"abstract":"This article introduces the composition and 12 operating conditions of a four-engine two-propeller hybrid power system. Through the combination of gearbox clutch and disconnection, the propulsion system has four single-engine operation modes, two double-engine parallel operation modes, and six PTI operation modes. Because the propulsion system has a variety of operating conditions, each operating condition has a form of energy transfer. As a result, its energy management and control are more complicated. To study the energy management and control strategy of a diesel- electric hybrid propulsion system, this work mainly studies the simulation model and sub-models of a diesel-electric hybrid propulsion system. In this study, MATLAB/ SIMULINK software is used to build the diesel engine model, motor model, and ship engine system mathematical model. The test and analysis were carried out on the test bench of the diesel-electric hybrid power system. By comparing the theoretical value of the SIMULINK simulation model with the test value of the test bench system, the correctness of each sub-model modeling method is verified. On the one hand, research on the text lays a theoretical foundation for the subsequent implementation of the conventional energy management and control strategy based on state identification on the unified management and distribution of the diesel-electric hybrid power system. At the same time, energy management of the diesel-electric hybrid system is also carried out. Optimization research provides theoretical guidance.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2020-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42381221","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：