The flow of water under wind-driven waves near the coast is highly energetic, leading to the production of chaotic, “turbulent” fluid motions. Turbulence plays an important role in the flow and the transport of sediment under waves. Therefore, understanding turbulence dynamics is crucial to understanding the behavior of waves and their effects on shoreline processes (e.g., beach erosion).
Previous research shows that the breaking of waves leads to a massive production of turbulent energy, but the vertical and horizontal spreading of turbulence is not properly understood. Through experiments in a large-scale wave flume, using acoustic and laser-based measurement instrumentation, Joep van der Zanden et al. (2018) systematically investigated the behavior of turbulent energy under breaking waves.
Results show that wave breaking alters turbulence dynamics over the full water column, from the water surface all the way down to the bed. Turbulence is spread horizontally and vertically by currents generated by the breaking wave. Moreover, wave breaking turbulence leads to the production of additional turbulence in the water column. The new insights in this paper can be used to further develop computational models for the flow and transport of sediment under breaking waves, ultimately contributing to better understanding of changes in beach profiles.
The full paper and a link to the data repository can be found at the website of Journal of Geophysical Research: Oceans (open access).
Published 27th February 2018.
Figure: Fluid circulation induced by the undertow: the main horizontal and vertical transport mechanism for wave breaking turbulence.