75th Annual Meeting of the APS Division of Fluid Dynamics (November 20, 2022 — November 22, 2022)

V0119: The Effect of Surfactants on a Plunging Breaker

  • Martin Erinin, Princeton University
  • Chang Liu, University of Maryland, College Park
  • Xinan Liu, University of Maryland, College Park
  • James Duncan, University of Maryland, College Park
DOI: https://doi.org/10.1103/APS.DFD.2022.GFM.V0119

In this video we show the free surface profile evolution for a deep-water plunging breaker in the presence of clean water (CLN) and three bulk concentrations of Triton-X 100 (TX1, TX2, TX3). The breakers are generated by a single programmable wave maker motion using a dispersively focused wave packet technique. Wave profiles are measured using laser induced fluorescence (LIF) and the surface tension is measured using a Langmuir trough. We found that in clean (CLN) and high surfactant concentration (TX3) cases the the plunging jet and entrained air cavity appear very smooth up to jet impact. However, in the TX1 case the jet curls inward and the air cavity becomes highly irregular while in the TX2 case no plunging jet is formed and no air entrained cavity appears, resulting in a spilling breaker. We hypothesize that this effect is because in the CLN and TX3 cases the surface tension along the jet surface is nearly constant, which results in a smooth jet and air cavity. While in the TX1 and TX2 cases the surface tension varies along the jet surface, which results in Marangoni stresses that influence the breaking process.

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