Hydroelasticity in Marine Hull Bottom Panels - Modeling and Characterization

Abstract: 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 e?ciency of high-speed craft by application of more re?ned 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 ?nite element code LS-DYNA. For the modeling of the panel-water impact situations a generalized approach for determination of ?uid discretization and contact parameters is derived and extensively used throughout this work. The hydroelastic problem is studied through systematic series of numerical simulations regarding di?erent impact situations. The work advances the understanding of the hydroelastic problem and introduces concepts such as kinematic and inertia related hydroelastic e?ects. The work further presents hydroelastic e?ects 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 e?ects, and partly to inertia related added mass e?ects. The results further show that, the e?ects of hydroelasticity increase with increased impact velocity, increased panel width, decreased deadrise angle, decreased panel ?exural and in-plane sti?ness, and decreased rotational and in-plane ?xation 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 e?ect of hydroelasticity for panels with di?erent sti?nesses. The observed hydroelastic e?ects included changes in panel geometry, local velocity and hydrodynamic pressures. These e?ects also correlate with the observed hydroelastic e?ects from the numerical simulations.