Extreme coastal responses using focused wave groups: Overtopping and horizontal forces exerted on an inclined seawall

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dc.contributor.author Whittaker, Colin en
dc.contributor.author Fitzgerald, CJ en
dc.contributor.author Raby, AC en
dc.contributor.author Taylor, PH en
dc.contributor.author Borthwick, AGL en
dc.date.accessioned 2018-12-10T20:43:10Z en
dc.date.issued 2018-10 en
dc.identifier.citation Coastal Engineering 140:292-305 Oct 2018 en
dc.identifier.issn 0378-3839 en
dc.identifier.uri http://hdl.handle.net/2292/45006 en
dc.description.abstract Total wave group overtopping and maximum horizontal force responses are investigated for an idealised seawall/dike on a plane beach subject to compact focused wave attack, using both laboratory and numerical wave flumes. The wave group interactions have very short durations such that extraneous reflections from the wavemaker arrive long after the main interaction. These short test durations facilitate the use of large ensembles of tests to explore the sensitivity of overtopping and force responses to variations in focus location, phase angle at focus, and linear focus wave amplitude. The scope of the laboratory wave flume tests is broadened by accurate numerical simulation based on a 1DH hybrid Boussinesq-NLSW model. For a given focus location and linear focused wave amplitude, variations in phase lead to an order-of-magnitude change in the group overtopping volume. Substantial increases in overtopping volume owing to the use of linear wavemaker theory (compared to second order theory) are also observed. These observations have implications for phase-independent empirical relationships derived using linear paddle signals in physical experiments. Examination of the incidence of wave groups parametrically optimised for maximum (and minimum) overtopping volumes indicates that the overtopping volume may be optimised by minimising reflections of pre-overtopping waves within the group, while maximising the amplitude of the first overtopping bore. Numerical predictions of horizontal seawall forces are obtained using fluid impulse derivatives and hydrostatic pressures obtained from the shallow water model. Within the shallow water model framework, hydrodynamic force contributions included in the fluid impulse method are observed to be small relative to the hydrostatic pressure force. The parametric dependence of the horizontal (non-impulsive) forces on the seawall is very similar to that of the overtopping volumes, with clear ‘bands’ of large values observed as a function of phase and focus location (for a given amplitude). This suggests that the parametric optimisation of focused wave groups is a robust method for the investigation of multiple coastal responses such as overtopping, forces and runup. en
dc.publisher Elsevier en
dc.relation.ispartofseries Coastal Engineering en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. Previously published items are made available in accordance with the copyright policy of the publisher. en
dc.rights.uri https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm en
dc.rights.uri https://www.elsevier.com/journals/coastal-engineering/0378-3839/guide-for-authors#13300 en
dc.title Extreme coastal responses using focused wave groups: Overtopping and horizontal forces exerted on an inclined seawall en
dc.type Journal Article en
dc.identifier.doi 10.1016/j.coastaleng.2018.08.004 en
pubs.begin-page 292 en
pubs.volume 140 en
dc.rights.holder Copyright: Elsevier en
pubs.author-url https://www.sciencedirect.com/science/article/pii/S0378383918301613 en
pubs.end-page 305 en
dc.rights.accessrights http://purl.org/eprint/accessRights/OpenAccess en
pubs.subtype Article en
pubs.elements-id 751476 en
pubs.org-id Engineering en
pubs.org-id Civil and Environmental Eng en
pubs.record-created-at-source-date 2018-08-14 en
pubs.online-publication-date 2018-08-13 en

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