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Lookup NU author(s): Dr Simon Benson, Professor Bob Dow, Professor Richard Birmingham
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).
Estimating the forces acting on a high speed craft for structural assessment purposes is challenging due to the complex combination of hydrodynamic loads, which include wave pressures, slamming pressures and their load effects at a global ‘hull girder’ level. An experimental approach to validate the use of established strip theory methods for predicting the hydrodynamic wave pressure loads is presented here. A series of regular wave seakeeping tests on a small scale segmented hull model of a high speed craft were completed and compared to equivalent seakeeping calculations. Experiments were conducted with a 1:13.5 scale hull model of a 17-metre all weather lifeboat, which is typical of a high speed watercraft capable of operating in severe weather at exposed locations. The model is segmented into four sections, rigidly held together by an instrumented backbone beam which can measure shear force and bending moments at the segmentation points. The model was tested over a full range of operating speeds and wave encounter frequencies. Results are compared with two strip theory calculations, the first using a zero speed Green function and the second using a Rankine source method with a forward speed correction term. It is shown that the Green function strip theory provides better correlation at lower speeds (up to a Froude number of 0.4) and the Rankine source method is more appropriate at higher speeds. The experiments generally show good equivalence to calculations and demonstrate that strip theory gives reasonable predictions of the global bending moment, assuming linearity with the wave height. It is proposed that, for the purpose of defining extreme or design loads, or for interpreting full scale trial data, strip theory is an appropriate method to represent the hydrodynamic wave induced loads in displacement and semi-planing regimes. This unlocks the potential for strip theory to be used as part of a complete assessment of the extreme loading on a high speed craft by combining the wave induced loads with other significant load components including slamming pressures and transient global loads caused by slamming impacts.
Author(s): Prini F, Benson S, Dow RS, Phillips HJ, Sheppard PJ, Birmingham RW
Publication type: Article
Publication status: Published
Journal: Engineering Structures
Year: 2021
Volume: 231
Print publication date: 15/03/2021
Online publication date: 26/01/2021
Acceptance date: 14/12/2020
Date deposited: 20/01/2021
ISSN (print): 0141-0296
ISSN (electronic): 1873-7323
Publisher: Elsevier Ltd
URL: https://doi.org/10.1016/j.engstruct.2020.111738
DOI: 10.1016/j.engstruct.2020.111738
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