Tsunami Ping-Pong: Generating The Whole Tsunami Event

Abstract

Considerable progress has been made over the past two decades in modelling representative tsunami waves in the laboratory. Developments such as the pneumatic tsunami simulator, TS, (Chandler et al, 2021), large wave paddles (Schimmels et al, 2016) and pump driven systems (Goseberg et al, 2013) have allowed full incident tsunami time series to be reproduced at large enough scales to provide reliable physical modelling data. These developments have enabled new insights into the time-varying influence of tsunami waves on run-up (McGovern et al, 2018), buildings (Foster et al, 2017), coastal structures (McGovern et al, 2022) and in particular the scour of sediments around these structures (McGovern et al, 2019). These advances are changing the way engineers and others design and plan for tsunami. However we are still only modelling ‘half the story’. In all existing published studies, the experiments simulated the effect of a single incident wave. We have so far ignored two significant elements of real tsunami events. Firstly, the rundown or return flow and secondly, the effect of multiple waves within a wave train. Both these aspects are difficult to model physically, particularly as the return flow and subsequent waves require a representative topography downstream of a test section. In most facilities there is not enough flume left to create this overland topography. In addition, changing this bathymetry to represent different scenarios such as a coastal plain or a small foreshore and an inland cliff, requires significant modelling effort and cost. To solve these challenges we propose the use of two TSs facing each other with the test section in between. This concept is shown in Figure 1. This extended abstract presents data from initial trials of the dual TS system conducted at HR Wallingford in 2023 during a three-day test window as part of the MAKEWAVES collaboration. The importance of simulating the return flow from a tsunami is demonstrated through its influence on scour around a rectangular building.