For many years, I have been puzzled by the limiting form of solitary waves at the air/water interface and its consequence on wave breaking. It turns out that the air plays an important role. With my Chinese colleagues from the Institute of Mechanics, Chinese Academy of Sciences, and my old collaborator Prof. Jean-Marc Vanden-Broeck, we performed careful numerical simulations to study the limiting configuration of interfacial solitary waves. The details are presented in a paper that just came out in the Journal of Fluid Mechanics (https://doi.org/10.1017/jfm.2021.521)

Coastal Boulder Deposits (CBD) are large rocks transported on land by storm or tsunami waves. Because CBD are very durable they can provide long term records of coastal inundation, but quantifying the strength and source of inundation remains controversial. The recent paper of our research associates A. Kennedy, R. Cox and of the HIGHWAVE PI F. Dias published in Geophysical Research Letters (https://doi.org/10.1029/2020GL090775) uses many records of CBD found worldwide combined with wave climatology to determine the range of transport possible for storm-wave CBD, and then to compare present results to findings using older methodologies. It is found that these older methods can underestimate the potential for storm waves to create CBD, and some previously identified “tsunami” CBD may actually have been generated by storm waves.

The first scaled experiments to determine breaking wave impact modes and energies responsible for the transport of boulder clasts of O(100 t) positioned atop coastal cliff s were carried out at Ecole Centrale de Marseille (ECM) in February 2021. In the experiments, the influence of the breaking wave crest shape and of the energy contained in the breaking wave were investigated.

As part of the HIGHWAVE project we are delighted to announce that some recent work has been accepted for publication in the Journal of Marine Science and Engineering (Special issue on Extreme Waves). The work focuses on comparing the effects of the wave spectrum, computed using the Discrete Interaction Approximation (DIA) and the Webb–Resio–Tracy (WRT) methods, on statistical wave properties such as skewness and kurtosis. In addition, we investigate the minimum spatial domain size required to obtain meaningful statistical wave properties.

Last week we have seen a lot of reports in media about the phenomenal sea state off the west coast of Ireland. An example is The Skipper (a journal of the Irish & UK Fishing Industries) releasing an article claiming a recorded monster wave of 30 meters. RTE had a few articles, where excited surfers mention 18 meter waves. Met Eireann and the Marine Institute M6 buoy recorded a maximum individual wave height of 21.7 meters between 27 and 28 October, with significant wave height being 15.7 meters. These were the remnants of hurricane Epsilon, that brought the extreme waves to the Irish coasts. These values are phenomenal indeed.

These reports bring us to the long standing discussion on quality control of the data. Can we trust a single instrument measuring the wave height?

My Chinese colleagues from Shanghai Jiao Tong University performed nice experiments to study the interaction between a solitary wave and a finite horizontal plate submerged at a depth equal to 1/4 of the water depth. The spatial and temporal variation of the three-dimensional (3D) surface deformation were measured using a multi-lens stereo reconstruction system. The hydrodynamic loads were measured by underwater load cells. The plate-induced shoaling causes 3D wave focusing, leading to an increased maximum elevation along the streamwise centerline of the plate. The detailed wave focusing process and the influence of wave amplitude on focusing are presented in a paper that just came out in Physics of Fluids (https://doi.org/10.1063/5.0015903). A 6-stage loading process based on the maxima of vertical wave force and pitching moment is proposed. It is coupled with the synchronous surface deformation to reveal the loading mechanism. It proves that the vertical wave force on the plate reduces compared with the results from 2D experiments. The surface elevation and wave-induced load data provide an excellent benchmark for further studies on the 3D nonlinear interaction between a solitary wave and a submerged plate.

HIGHWAVE involves a lot of numerical simulations, dealing in particular with extreme sea states and using nonlinear wave propagation models. ICHEC, the Irish Centre for High-End Computing, provides core-hours to three kinds of projects. Class A projects are intended for consortia concerned with high impact problems. Prof. Dias was successful with his Class A application. The project has been given 5M core-hours. It will start on 1 June 2020 and will last for a couple of years. 

In these dark times, when good news is scarce, science always pushes the boundaries and offers hope…

The world record set by Engineer Arnaud Disant and his team in 2018 has now been officially verified: offshore WiFi transmission of 19.4 nautical miles off Cork harbour, “The longest ever attempted transmission between a vessel offshore and a lighthouse on a distant shore, without using satellite communication of cellular data like 3G or 4G…”