Pneumatic Long-Wave Generation of Tsunami-Length Waveforms and their Runup

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 to 230 seconds and wave amplitudes between 0.03 to 0.14 metres in water depths of 0.7 to 1.0 metres. Using Froude similitude in scaling, at scale 1:50, these laboratory waves are theoretically dynamically equivalent to prototype tsunami waveforms with periods between 1 to 27 minutes and positive wave amplitude between 1.5 to 7.0 metres 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 (≈ 9:5 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'.