The arrows indicate the strength and direction of water flow at each point of a breaking wave, or ‘bore’. | Graphic: D. Wüthrich et al. (2021)

The foamy features of breaking waves (‘bores’ in scientific parlance) only exist for a few fractions of a second. The civil engineer Davide Wüthrich has now captured and classified these ephemeral structures for the first time, using an ultra-high-speed video camera. He has thereby also been able to measure the flow velocities at the surface of a breaking wave (see the small white arrows).

D. Wüthrich et al.: Strong free-surface turbulence in breaking bores: a physical study on the free-surface dynamics and air–water interfacial features. Journal of Fluid Mechanics (2021)

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