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Pneumatic long-wave generation of tsunami-length waveforms and their runup

McGovern, DJ; Robinson, T; Chandler, ID; Allsop, W; Rossetto, T; (2018) Pneumatic long-wave generation of tsunami-length waveforms and their runup. Coastal Engineering , 138 pp. 80-97. 10.1016/j.coastaleng.2018.04.006. Green open access

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Abstract

An experimental study is conducted using a pneumatic long-wave generator (also known as a Tsunami Generator). Scaled tsunami waveforms are produced with periods in the range of 5–230 s and wave amplitudes between 0.03 and 0.14 m in water depths of 0.7–1.0 m. Using Froude similitude in scaling, at scale 1:50, these laboratory waves are theoretically dynamically equivalent to prototype tsunami waveforms with periods between 1 and 27 min and positive wave amplitude between 1.5 and 7.0 m in water depths of 50 m. The purpose of these tests is to demonstrate that the pneumatic method can generate long waves in relatively short flumes and to investigate their runup. Standard wave parameters, (free-surface, wave celerity and velocity profiles) are used to characterise the waveforms. It is shown that for the purpose of runup and onshore ingression, minimal interference from the re-reflected waves is observed. By generating tsunami waveforms with periods greater than 80 s ( mins prototype scale) the available experimental data set is expanded and used to develop a new runup equation. Contrary to the shorter waves, shoaling of these longer waves is insignificant. For waveforms with periods greater 100 s the runup is best described by wave steepness not potential energy. When tested against available runup equations the results are mixed; most perform poorly for scaled tsunami length periods. A segmented regression analysis is performed on the data set and an empirical runup relationship is provided based on a new parameter termed the ‘Relative Slope Length’. The tests show the definition of offshore wave amplitude is non-trivial and may greatly affect the predicted relative runup of a given wave. It is noted that this appears to be a general issue for all types of tsunami simulation in the laboratory. Together these observations and proposed runup model provide a framework for future numerical studies of the topic.

Type: Article
Title: Pneumatic long-wave generation of tsunami-length waveforms and their runup
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.coastaleng.2018.04.006
Publisher version: https://doi.org/10.1016/j.coastaleng.2018.04.006
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Experiments, , Pneumatic generation, Long wave,Tsunami, Runup
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Civil, Environ and Geomatic Eng
URI: https://discovery.ucl.ac.uk/id/eprint/10061534
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