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Hydroelasticity in Marine Hull Bottom Panels - Modeling and Characterization
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems. (Marina system)ORCID iD: 0000-0001-7542-3225
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The work in this thesis is concerned with the localized problem of hydroelasticity in marine panel-water impacts with an overall aim to increase the efficiency of high-speed craft by application of more refined methods in the structural design. The work mainly focuses on numerical modeling of the hydroelastic problem and therewith related aspects in the modeling and characterization of hydroelasticity. In addition, the work also addresses aspects regarding design methods of high-speed craft and experimental analysis of hydroelasticity.

Two-dimensional panel-water impacts are simulated by using the commercial finite element code LS-DYNA. For the modeling of the panel-water impact situations a generalized approach for determination of fluid discretization and contact parameters is derived and extensively used throughout this work. The hydroelastic problem is studied through systematic series of numerical simulations regarding different impact situations. The work advances the understanding of the hydroelastic problem and introduces concepts such as kinematic and inertia related hydroelastic effects. The work further presents hydroelastic effects in contrast to previously published results, in the sense that it may not be conservative to ignore hydroelasticity in the structural design. This increase in the structural response when accounting for hydroelasticity can partly be related to kinematic effects, and partly to inertia related added mass effects. The results further show that, the effects of hydroelasticity increase with increased impact velocity, increased panel width, decreased deadrise angle, decreased panel flexural and in-plane stiffness, and decreased rotational and in-plane fixation at the boundaries.

A tentative method is derived to characterize the hydroelastic problem, which, despite its simplicity and limitations, is found to successfully capture the complexity of the hydroelastic interaction in the design of the experimental setup. The experimental water slam testing of composite hull panels are conducted to study the effect of hydroelasticity for panels with different stiffnesses. The observed hydroelastic effects included changes in panel geometry, local velocity and hydrodynamic pressures. These effects also correlate with the observed hydroelastic effects from the numerical simulations.

 

Place, publisher, year, edition, pages
Stockholm: KTH , 2009. , xi, 20 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2009:42
Keyword [en]
fluid-structure interaction, hydroelasticity, hull-water impact, high-speed craft, slamming, explicit finite element methods
National Category
Vehicle Engineering
Identifiers
URN: urn:nbn:se:kth:diva-10903ISBN: 978-91-7415-389-7 (print)OAI: oai:DiVA.org:kth-10903DiVA: diva2:229405
Public defence
2009-09-16, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:15 (English)
Opponent
Supervisors
Note
QC 20100810Available from: 2009-09-02 Created: 2009-08-12 Last updated: 2010-08-10Bibliographically approved
List of papers
1. On Structural Design of Energy Efficient Small High-Speed Craft
Open this publication in new window or tab >>On Structural Design of Energy Efficient Small High-Speed Craft
2011 (English)In: Marine Structures, ISSN 0951-8339, E-ISSN 1873-4170, Vol. 24, no 1, 43-59 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents an integrated design procedure for determination of structural arrangement and scantlings for the complete structure of small high-speed craft. The purpose of the procedure is to serve as a tool in the preliminary design stage where it enables generation of weight minimized designs with very limited effort. The design procedure is applied in a material concept study for a high-speed patrol craft. The various concepts include single skin and sandwich composites, aluminum and steel. It is demonstrated that the mass of the aluminum hull structure can be reduced from the original 11.7 tonnes to 9.6 tonnes through application of the presented design procedure. The most weight efficient material concept is a carbon-fiber foam-cored sandwich with a structural mass of 4.8 tonnes, which is about 50% less than the refined aluminum version. Through simple hydromechanic analysis, potential for fuel and CO2 emission reductions of 8% for the refined aluminum version and 27% for the carbon-fiber sandwich version in relation to the original craft are indicated.

Keyword
High-speed craft, Integrated design procedure, Scantlings, Weight minimization, Composites, Material concepts
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-10990 (URN)10.1016/j.marstruc.2011.01.001 (DOI)000289124100003 ()2-s2.0-79952444468 (Scopus ID)
Note
QC 20100810 Uppdaterad från submitted till published (201100419).Available from: 2009-09-02 Created: 2009-09-02 Last updated: 2017-12-13Bibliographically approved
2. Explicit FE-modelling of fluid-structure interaction in hull-water impacts
Open this publication in new window or tab >>Explicit FE-modelling of fluid-structure interaction in hull-water impacts
2006 (English)In: International Shipbuilding Progress, ISSN 0020-868X, E-ISSN 1566-2829, Vol. 53, no 2, 103-121 p.Article in journal (Refereed) Published
Abstract [en]

The paper considers explicit FE-modelling of fluid-structure interaction in hull-water impacts. To minimize the variables studied and to enable comparison with analytical methods, the problem is here idealised as a two-dimensional rigid wedge impacting on a calm water surface. A parameter study is performed, where the sensitivity in the mesh resolution and the contact parameter selection is investigated. It is concluded that a numerically stable non-leaking solution to the hull-water impact problem, with good correlation to analytical results, is achievable. It is however also concluded that application of this modelling technique can be costly and far from trivial. The solution is for example highly dependent on the relation between mesh-density and contact-stiffness. Successful modelling hence requires rational approaches for determination of fluid discretization and contact parameters. By making reference to an analytical solution of the hull-water impact problem, the results from the parameter study are generalised, and a rational approach for determination of fluid discretization and contact parameters in the modelling of arbitrary hull-water impact situations is presented. The generality of the approach is favourably demonstrated for different impact angles and velocities.

Keyword
Explicit FEA; Fluid-structure interaction; High-speed craft; Hull-water impact; Slamming
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-6876 (URN)2-s2.0-34547546367 (Scopus ID)
Note
QC 20100810Available from: 2007-03-13 Created: 2007-03-13 Last updated: 2017-12-14Bibliographically approved
3. Explicit FE-modelling of hydroelasticity in panel-water impacts
Open this publication in new window or tab >>Explicit FE-modelling of hydroelasticity in panel-water impacts
2007 (English)In: International Shipbuilding Progress, ISSN 0020-868X, E-ISSN 1566-2829, Vol. 54, no 2-3, 111-127 p.Article in journal (Refereed) Published
Abstract [en]

This paper considers modelling of hydroelasticity in water impacts of ship-hull bottom-panels by use of explicit finite element methods. The finite element analysis is based on a multi-material arbitrary Lagrangian-Eulerian formulation and a penalty contact algorithm. This modelling technique enables the modelling of the instantaneous fluid-structure interaction. The FE-modelling of elastic panel-water impacts is evaluated by a convergence study and by comparison with experiments. Hydroelastic effects on the panel response are systematically studied for different impact velocities, boundary conditions and structural mass. It is concluded that hydroelastic effects can result in a significant reduction of the structural response for certain combinations of panel deadrise, impact velocity and boundary conditions. Inertia effects are shown to be dominated by added water mass. The present study is compared with other published work concerning hydroelasticity in panel-water impacts.

Keyword
Explicit finite element modelling; Fluid-structure interaction; High-speed craft; Hull-water impact; Hydroelasticity; Slamming
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-6877 (URN)2-s2.0-35148831820 (Scopus ID)
Note
QC 20100810Available from: 2007-03-13 Created: 2007-03-13 Last updated: 2017-12-14Bibliographically approved
4. Hydroelasticity in Marine Hull Bottom Panels
Open this publication in new window or tab >>Hydroelasticity in Marine Hull Bottom Panels
2009 (English)Article in journal (Refereed) Submitted
Abstract [en]

The paper considers the hydroelastic interaction involved in panel- water impacts of high-speed craft. Hydroelastic panel-water impacts are simulated by using the finite element code LS-DYNA and a simplified in- house developed method. The mechanisms involved in the problem are stud- ied by a systematic series of simulations regarding different impact veloc- ities, deadirse angels, boundary conditions, membrane effects, and panel properties. The significance of hydroelasticity on the problem is studied by comparing with methods addressing the problem as completely separable and quasi-static. It is shown that membrane effects can have a large influ- ence on the hydroelastic problem. The results further show that, accounting for hydroelasticity may yield larger maximum deflections and strains com- pared to completely separated and quasi-static solutions. The increase in the structural response when accounting for hydroelasticity can partly be explained by kinematic boundary condition effects, and partly by inertia related added mass effects.

Keyword
hydroelastic, fluid-structure interaction, dynamic charac- terization, slamming, high-speed craft
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-10991 (URN)
Note
QS 20120315Available from: 2009-09-02 Created: 2009-09-02 Last updated: 2012-03-15Bibliographically approved
5. Effects of Panel Stiffness on Slamming Responses of Composite Hull Panels
Open this publication in new window or tab >>Effects of Panel Stiffness on Slamming Responses of Composite Hull Panels
Show others...
2009 (English)In: 17th International Conference on Composite Materials, ICCM17, 2009, 1-11 p.Conference paper, Published paper (Refereed)
Abstract [en]

Controlled water slam testing of composite hull panels was conducted to study the effect of hydroelasticity for three panels with different stiffnesses. The experimental methodology successfully characterised the hydroelastic behaviour, which included kinematic as well as inertial effects. Hydroelastic effects included changes in panel geometry, local velocity, fluid pressures, and panel structural responses.

Keyword
Dynamic, Experiments, Hydroelasticity, Marine, Panel, Sandwich, Slamming
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-10992 (URN)2-s2.0-80052045247 (Scopus ID)
Conference
17th International Conference on Composite Materials, ICCM-17; Edinburgh; United Kingdom; 27 July 2009 through 31 July 2009
Note

QC 20100810

Available from: 2009-09-02 Created: 2009-09-02 Last updated: 2014-09-26Bibliographically approved

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