Experimental and numerical investigation on the runup of leading-depression N-waves

Dr. Peter Lo, Assistant Professor
Department of Engineering Science and Ocean Engineering
National Taiwan University

Location Information
**This seminar will be held over Zoom only**
Meeting ID: 961 6222 2366
Passcode: OREseminar
https://hawaii.zoom.us/j/96162222366

Solitary waves, widely used benchmark waves in hydrodynamic studies, had historically been implied as a suitable wave form for tsunamis. However, modern tsunami records reveal solitary waves to be an inaccurate model for real tsunamis. For example, before the arrival of a tsunami at shore, a significant recession of water is often observed. Solitary waves are incapable of capturing this drawdown phenomenon, and the leading-depression N-waves (LDNs) are often used instead. Due to the elusive nature of LDNs, to date a comprehensive study on LDNs is still lacking. In this study, we utilize a combination of laboratory experiments and numerical simulations to investigate the runup of LDNs. Emphasis is placed on comparing the runup process of an LDN to that of the solitary wave with the same wave height. The main findings are: 1) for non-breaking waves, a steeper wave front results in a larger runup; 2) for breaking waves, an LDN causes a lower runup than the corresponding solitary wave due to a more intense wave breaking process; 3) bore-like LDNs cause higher runup than solitary waves. Overall, the water drawdown phenomenon is found to have only mild effects on wave runup. Nonetheless, the water drawdown phenomenon tends to increase the intensity of wave breaking, thus potentially causing greater damage in the swash zone.