Pub Date : 2018-02-28DOI: 10.1080/09377255.2018.1441781
C. Fischer, W. Fricke, C. Rizzo
ABSTRACT This paper deals with the fatigue assessment of three ship structural details. While local approaches, which are proposed in relevant literature and which nowadays are also widely applied in design practice, can successfully assess the fatigue strength of several welded joints, web-stiffened complex geometries show peculiar features, needing to bias the results of local approaches. Hence, even recent rule requirements need to include correction factors to account for such deviations. The present study identifies effects, which alter particularly the crack propagation behaviour. Some test cases were re-evaluated using approaches referring to the effective notch stress and to the strain energy density. Results are compared with the test results in order to provide explanations to the above-mentioned biased assessments.
{"title":"Fatigue assessment of web-stiffened corners in plated structures by local approaches","authors":"C. Fischer, W. Fricke, C. Rizzo","doi":"10.1080/09377255.2018.1441781","DOIUrl":"https://doi.org/10.1080/09377255.2018.1441781","url":null,"abstract":"ABSTRACT This paper deals with the fatigue assessment of three ship structural details. While local approaches, which are proposed in relevant literature and which nowadays are also widely applied in design practice, can successfully assess the fatigue strength of several welded joints, web-stiffened complex geometries show peculiar features, needing to bias the results of local approaches. Hence, even recent rule requirements need to include correction factors to account for such deviations. The present study identifies effects, which alter particularly the crack propagation behaviour. Some test cases were re-evaluated using approaches referring to the effective notch stress and to the strain energy density. Results are compared with the test results in order to provide explanations to the above-mentioned biased assessments.","PeriodicalId":51883,"journal":{"name":"Ship Technology Research","volume":"65 1","pages":"69 - 78"},"PeriodicalIF":2.2,"publicationDate":"2018-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09377255.2018.1441781","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43413768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-02-26DOI: 10.1080/09377255.2018.1442193
Youjiang Wang, M. Abdel‐Maksoud
ABSTRACT The 2D remeshed vortex method with the Brinkman penalisation scheme is applied to the simulation of flow around 2D cylinder and foil at the Reynolds number . The dependences of the hydrodynamic forces on domain dimension, mesh size and time step are analysed. The results are compared with those obtained with the commercially available finite volume CFD solver CFX. The computation time is also presented. It is observed that the remeshed vortex method does not suffer from the blockage effect, and thus is potentially suitable for the simulation of flow with far-field boundary conditions. However, it has only a first-order accuracy with regard to time step, and therefore needs a quite small time step to acquire reliable hydrodynamic forces.
{"title":"Application of the remeshed vortex method to the simulation of 2D flow around circular cylinder and foil","authors":"Youjiang Wang, M. Abdel‐Maksoud","doi":"10.1080/09377255.2018.1442193","DOIUrl":"https://doi.org/10.1080/09377255.2018.1442193","url":null,"abstract":"ABSTRACT The 2D remeshed vortex method with the Brinkman penalisation scheme is applied to the simulation of flow around 2D cylinder and foil at the Reynolds number . The dependences of the hydrodynamic forces on domain dimension, mesh size and time step are analysed. The results are compared with those obtained with the commercially available finite volume CFD solver CFX. The computation time is also presented. It is observed that the remeshed vortex method does not suffer from the blockage effect, and thus is potentially suitable for the simulation of flow with far-field boundary conditions. However, it has only a first-order accuracy with regard to time step, and therefore needs a quite small time step to acquire reliable hydrodynamic forces.","PeriodicalId":51883,"journal":{"name":"Ship Technology Research","volume":"65 1","pages":"79 - 86"},"PeriodicalIF":2.2,"publicationDate":"2018-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09377255.2018.1442193","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49596378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-01-02DOI: 10.1080/09377255.2017.1411001
J. Kröger, Niklas Kühl, T. Rung
ABSTRACT The paper is concerned with simulation-based shape optimisation in marine engineering flows. Attention is devoted to the derivation of an adjoint complement to two-phase flow finite-volume procedures. The strategy refers to an extension of a hybrid continuous/discrete adjoint method for volume-of-fluid (VoF) approaches. The study outlines means to formulate a discrete adjoint VoF scheme from the terms that originate from variations of the fluid properties. The adjoint solution is verified against results of a direct differentiation technique. The application is devoted to the drag optimisation of the Kriso container ship. A kernel-based self-parametrisation approach of the design surface is combined with mesh-morphing techniques to drive the 150,000 shape parameters of the vessel without the need to revisit or differentiate the CAD environment during the optimisation. The optimisation process obeys to practical constraints. The optimised vessel displays more than 5% reduction of total drag while maintaining main dimensions and displacement.
{"title":"Adjoint volume-of-fluid approaches for the hydrodynamic optimisation of ships","authors":"J. Kröger, Niklas Kühl, T. Rung","doi":"10.1080/09377255.2017.1411001","DOIUrl":"https://doi.org/10.1080/09377255.2017.1411001","url":null,"abstract":"ABSTRACT The paper is concerned with simulation-based shape optimisation in marine engineering flows. Attention is devoted to the derivation of an adjoint complement to two-phase flow finite-volume procedures. The strategy refers to an extension of a hybrid continuous/discrete adjoint method for volume-of-fluid (VoF) approaches. The study outlines means to formulate a discrete adjoint VoF scheme from the terms that originate from variations of the fluid properties. The adjoint solution is verified against results of a direct differentiation technique. The application is devoted to the drag optimisation of the Kriso container ship. A kernel-based self-parametrisation approach of the design surface is combined with mesh-morphing techniques to drive the 150,000 shape parameters of the vessel without the need to revisit or differentiate the CAD environment during the optimisation. The optimisation process obeys to practical constraints. The optimised vessel displays more than 5% reduction of total drag while maintaining main dimensions and displacement.","PeriodicalId":51883,"journal":{"name":"Ship Technology Research","volume":"65 1","pages":"47 - 68"},"PeriodicalIF":2.2,"publicationDate":"2018-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09377255.2017.1411001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46758722","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-01-02DOI: 10.1080/09377255.2017.1399970
A. Mofidi, J. E. Martin, P. Carrica
ABSTRACT This paper investigates a coupled computational fluid dynamics (CFD)/potential propeller code approach to simulate maneuvers of ships. While this approach is successful in submarines, the concept has not been evaluated before for cases where an object (the rudder) is immersed in the wake. The study uses the CFD code REX and the propeller code PUF-14 applied to propeller/rudder interactions in open water configuration and to a 15/1 zigzag maneuver for the KCS container ship. Self-propulsion results, and motions, forces, moments and mean flow field during the maneuver agree well with experiments and discretized propeller simulations. The approach is an effective and economical way to perform direct simulation of surface ship maneuvers, providing CPU time savings approaching an order of magnitude. Massively separated rudder flows may not perform as well, since the propeller turbulence reaching the rudder is under-predicted in the coupled approach.
{"title":"Propeller/rudder interaction with direct and coupled CFD/potential flow propeller approaches, and application to a zigzag manoeuvre","authors":"A. Mofidi, J. E. Martin, P. Carrica","doi":"10.1080/09377255.2017.1399970","DOIUrl":"https://doi.org/10.1080/09377255.2017.1399970","url":null,"abstract":"ABSTRACT This paper investigates a coupled computational fluid dynamics (CFD)/potential propeller code approach to simulate maneuvers of ships. While this approach is successful in submarines, the concept has not been evaluated before for cases where an object (the rudder) is immersed in the wake. The study uses the CFD code REX and the propeller code PUF-14 applied to propeller/rudder interactions in open water configuration and to a 15/1 zigzag maneuver for the KCS container ship. Self-propulsion results, and motions, forces, moments and mean flow field during the maneuver agree well with experiments and discretized propeller simulations. The approach is an effective and economical way to perform direct simulation of surface ship maneuvers, providing CPU time savings approaching an order of magnitude. Massively separated rudder flows may not perform as well, since the propeller turbulence reaching the rudder is under-predicted in the coupled approach.","PeriodicalId":51883,"journal":{"name":"Ship Technology Research","volume":"65 1","pages":"10 - 31"},"PeriodicalIF":2.2,"publicationDate":"2018-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09377255.2017.1399970","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47868085","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-01-02DOI: 10.1080/09377255.2017.1394563
Min Xiao, Yufan Fu
ABSTRACT In this paper, the flow of liquid LNG in the nozzle is analyzed, and the results are taken as the initial conditions and boundary conditions for LNG spray calculation. On this basis, a numerical simulation model of pure liquid LNG flash boiling spray was created to investigate the development of the spray process. The temperature of LNG, the injection pressure and the ambient pressure are studied by the method of AVL-FIRE software.The results showthat, with the increase of the injection pressure, the spray penetration and spray angle is increased and the Sauter mean diameter (SMD) is decreased distinctly. With the increase of the injection pressure, the spray penetration and spray angle is increased and the SMD is decreased distinctly. Ensure that keeping the other conditions, rising LNG temperature and reducing the ambient pressure, the flash boiling phenomenon will be more acute and the atomization quality will be improved.
{"title":"Numerical simulation research on the LNG flash boiling spray","authors":"Min Xiao, Yufan Fu","doi":"10.1080/09377255.2017.1394563","DOIUrl":"https://doi.org/10.1080/09377255.2017.1394563","url":null,"abstract":"ABSTRACT In this paper, the flow of liquid LNG in the nozzle is analyzed, and the results are taken as the initial conditions and boundary conditions for LNG spray calculation. On this basis, a numerical simulation model of pure liquid LNG flash boiling spray was created to investigate the development of the spray process. The temperature of LNG, the injection pressure and the ambient pressure are studied by the method of AVL-FIRE software.The results showthat, with the increase of the injection pressure, the spray penetration and spray angle is increased and the Sauter mean diameter (SMD) is decreased distinctly. With the increase of the injection pressure, the spray penetration and spray angle is increased and the SMD is decreased distinctly. Ensure that keeping the other conditions, rising LNG temperature and reducing the ambient pressure, the flash boiling phenomenon will be more acute and the atomization quality will be improved.","PeriodicalId":51883,"journal":{"name":"Ship Technology Research","volume":"65 1","pages":"1 - 9"},"PeriodicalIF":2.2,"publicationDate":"2018-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09377255.2017.1394563","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48381813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-01-02DOI: 10.1080/09377255.2017.1407545
D. Peri
ABSTRACT Among the different techniques for interpolation/approximation of sparse data, Spline interpolation represents one of the most popular alternatives. It is largely used for one-dimensional and two-dimensional problems, but the use in case of multi-dimensional datasets, where the space dimension is larger than 2, is not common. The necessity of a topology for the sample data, so that the proximal points are clearly identified, put some difficulties even in . Furthermore, the classical Spline algorithms are not straightforward to implement, so that for this reason probably they are not widely applied in ship design optimisation, and other interpolation techniques are much more popular. In this paper, some elements of Spline interpolation theory are presented in order to produce a simple and efficient multi-dimensional interpolation method, easy to implement.
{"title":"Easy-to-implement multidimensional spline interpolation with application to ship design optimisation","authors":"D. Peri","doi":"10.1080/09377255.2017.1407545","DOIUrl":"https://doi.org/10.1080/09377255.2017.1407545","url":null,"abstract":"ABSTRACT Among the different techniques for interpolation/approximation of sparse data, Spline interpolation represents one of the most popular alternatives. It is largely used for one-dimensional and two-dimensional problems, but the use in case of multi-dimensional datasets, where the space dimension is larger than 2, is not common. The necessity of a topology for the sample data, so that the proximal points are clearly identified, put some difficulties even in . Furthermore, the classical Spline algorithms are not straightforward to implement, so that for this reason probably they are not widely applied in ship design optimisation, and other interpolation techniques are much more popular. In this paper, some elements of Spline interpolation theory are presented in order to produce a simple and efficient multi-dimensional interpolation method, easy to implement.","PeriodicalId":51883,"journal":{"name":"Ship Technology Research","volume":"65 1","pages":"32 - 46"},"PeriodicalIF":2.2,"publicationDate":"2018-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09377255.2017.1407545","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45815720","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-11-01Epub Date: 2016-11-14DOI: 10.1007/s10198-016-0843-9
D Cattel, R C van Kleef, R C J A van Vliet
Many health insurance schemes include deductibles to provide consumers with cost containment incentives (CCI) and to counteract moral hazard. Policymakers are faced with choices on the implementation of a specific cost sharing design. One of the guiding principles in this decision process could be which design leads to the strongest CCI. Despite the vast amount of literature on the effects of cost sharing, the relative effects of specific cost sharing designs-e.g., a traditional deductible versus a doughnut hole-will mostly be absent for a certain context. This papers aims at developing a simulation model to approximate the relative effects of different deductible modalities on the CCI. We argue that the CCI depends on the probability that healthcare expenses end up in the deductible range and the expected healthcare expenses given that they end up in the deductible range. Our empirical application shows that different deductible modalities result in different CCIs and that the CCI under a certain modality differs across risk-groups.
许多医疗保险计划都包含免赔额，为消费者提供成本控制激励（CCI），并抵消道德风险。政策制定者面临着实施特定费用分担设计的选择。决策过程中的指导原则之一可能是哪种设计能带来最强的 CCI。尽管有大量文献研究费用分担的效果，但特定费用分担设计的相对效果（如传统的免赔额与甜甜圈洞）在特定情况下大多不存在。本文旨在建立一个模拟模型，以近似分析不同免赔额模式对 CCI 的相对影响。我们认为，CCI 取决于医疗费用最终进入免赔额范围的概率，以及医疗费用最终进入免赔额范围后的预期医疗费用。我们的实证应用表明，不同的免赔额模式会导致不同的 CCI，而且不同风险群体在某种模式下的 CCI 也不同。
{"title":"A method to simulate incentives for cost containment under various cost sharing designs: an application to a first-euro deductible and a doughnut hole.","authors":"D Cattel, R C van Kleef, R C J A van Vliet","doi":"10.1007/s10198-016-0843-9","DOIUrl":"10.1007/s10198-016-0843-9","url":null,"abstract":"<p><p>Many health insurance schemes include deductibles to provide consumers with cost containment incentives (CCI) and to counteract moral hazard. Policymakers are faced with choices on the implementation of a specific cost sharing design. One of the guiding principles in this decision process could be which design leads to the strongest CCI. Despite the vast amount of literature on the effects of cost sharing, the relative effects of specific cost sharing designs-e.g., a traditional deductible versus a doughnut hole-will mostly be absent for a certain context. This papers aims at developing a simulation model to approximate the relative effects of different deductible modalities on the CCI. We argue that the CCI depends on the probability that healthcare expenses end up in the deductible range and the expected healthcare expenses given that they end up in the deductible range. Our empirical application shows that different deductible modalities result in different CCIs and that the CCI under a certain modality differs across risk-groups.</p>","PeriodicalId":51883,"journal":{"name":"Ship Technology Research","volume":"63 1","pages":"987-1000"},"PeriodicalIF":0.0,"publicationDate":"2017-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5602006/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81935707","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-09-02DOI: 10.1080/09377255.2017.1392073
Sören Ehlers, Fai Cheng, I. Jordaan, W. Kühnlein, P. Kujala, Yuejian Luo, R. Freeman, K. Riska, J. Sirkar, Yeong-Tae Oh, K. Terai, J. Valkonen
ABSTRACT Structures used in Arctic regions must comply with ice-induced loading without failure, asset loss, or loss of life. Current structural design regulations, particularly for ships, rely primarily on the experience gained from first-year ice, e.g. in the Baltic Sea. Therefore, this paper presents first, the most relevant design rules for both ships and offshore structures, and second, first principle-based pressure and occurrence determination methods to obtain corresponding scantlings. To demonstrate these first principle-based methods, the design ice load is assessed for a transit operation along the Northern Sea Route. In conclusion, this paper seeks to motivate a more mission-based design methodology, in addition to the present design methods, using the presented first principle-based methods. The paper is based on the ISSC 2015 V.6 Arctic Technology committee report.
{"title":"Towards mission-based structural design for arctic regions","authors":"Sören Ehlers, Fai Cheng, I. Jordaan, W. Kühnlein, P. Kujala, Yuejian Luo, R. Freeman, K. Riska, J. Sirkar, Yeong-Tae Oh, K. Terai, J. Valkonen","doi":"10.1080/09377255.2017.1392073","DOIUrl":"https://doi.org/10.1080/09377255.2017.1392073","url":null,"abstract":"ABSTRACT Structures used in Arctic regions must comply with ice-induced loading without failure, asset loss, or loss of life. Current structural design regulations, particularly for ships, rely primarily on the experience gained from first-year ice, e.g. in the Baltic Sea. Therefore, this paper presents first, the most relevant design rules for both ships and offshore structures, and second, first principle-based pressure and occurrence determination methods to obtain corresponding scantlings. To demonstrate these first principle-based methods, the design ice load is assessed for a transit operation along the Northern Sea Route. In conclusion, this paper seeks to motivate a more mission-based design methodology, in addition to the present design methods, using the presented first principle-based methods. The paper is based on the ISSC 2015 V.6 Arctic Technology committee report.","PeriodicalId":51883,"journal":{"name":"Ship Technology Research","volume":"34 8","pages":"115 - 128"},"PeriodicalIF":2.2,"publicationDate":"2017-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09377255.2017.1392073","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41275401","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-09-02DOI: 10.1080/09377255.2017.1392074
V. Shigunov
ABSTRACT The second-generation intact stability criteria developed at IMO consist of three alternative assessments: level 1, level 2 and a direct stability assessment (DSA). In a probabilistic DSA, the probability of stability failure is used as a criterion, which requires some form of counting of stability failure events and therefore, requires very long simulation time. The paper studies several possibilities to simplify DSA and thus enables its use in practical design approval: extrapolation of the average time to stability failure over wave height, reduction of the number of assessment cases to few selected design situations, and use of non-probabilistic safety criteria. The results show that the extrapolation leads to sufficiently accurate results; however, outliers may require manual control; the design situations’ method provides sufficiently accurate results while significantly reducing the number of required simulations; non-probabilistic assessment significantly reduces simulation time but leads to a significant scatter of the assessment results.
{"title":"Direct stability assessment: pragmatic solutions","authors":"V. Shigunov","doi":"10.1080/09377255.2017.1392074","DOIUrl":"https://doi.org/10.1080/09377255.2017.1392074","url":null,"abstract":"ABSTRACT The second-generation intact stability criteria developed at IMO consist of three alternative assessments: level 1, level 2 and a direct stability assessment (DSA). In a probabilistic DSA, the probability of stability failure is used as a criterion, which requires some form of counting of stability failure events and therefore, requires very long simulation time. The paper studies several possibilities to simplify DSA and thus enables its use in practical design approval: extrapolation of the average time to stability failure over wave height, reduction of the number of assessment cases to few selected design situations, and use of non-probabilistic safety criteria. The results show that the extrapolation leads to sufficiently accurate results; however, outliers may require manual control; the design situations’ method provides sufficiently accurate results while significantly reducing the number of required simulations; non-probabilistic assessment significantly reduces simulation time but leads to a significant scatter of the assessment results.","PeriodicalId":51883,"journal":{"name":"Ship Technology Research","volume":"64 1","pages":"144 - 162"},"PeriodicalIF":2.2,"publicationDate":"2017-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09377255.2017.1392074","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48830075","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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