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High-resolution direct simulation of deep water breaking waves: transition to turbulence, bubbles and droplets production

Abstract : We present high-resolution three-dimensional direct numerical simulations of breaking waves solving for the two-phase Navier-Stokes equations. We investigate the role of the Reynolds (wave inertia relative to viscous effects) and Bond numbers (wave scale over the capillary length) on the energy, bubble and droplet statistics of strong plunging breakers. We explore the asymptotic regimes at high Reynolds and Bond numbers and compare with laboratory breaking waves. Energetically, the breaking wave transitions from laminar to three-dimensional turbulent flow on a timescale that depends on the turbulent Reynolds number up to a limiting value of Re λ ∼ 100, consistent with the mixing transition in other canonical turbulent flows. We characterize the role of capillary effects on the impacting jet and ingested main cavity shape and subsequent fragmentation process, and extend the buoyant-energetic scaling from Deike et al. (2016) to account for the cavity shape and its scale separation from the Hinze scale, r H. We confirm two regimes in the bubble size distribution, N (r/r H) ∝ (r/r H) −10/3 for bubbles above r H , and N (r/r H) ∝ (r/r H) −3/2 below it. We show resolved bubbles up to one order of magnitude below the Hinze scale and observe a good collapse of the numerical data compared to laboratory breaking waves (Deane & Stokes 2002). We resolve droplet statistics at high Bond number in good agreement with recent experiments (Erinin et al. 2019), with a distribution shape close to N d (r d) ∝ r −2 d. The evolution of the droplet statistics appears controlled by the details of the impact process and subsequent splash-up. We discuss velocity distributions for the droplets, finding ejection velocities up to four times the phase speed of the wave, which are produced during the most intense splashing events of the breaking process.
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https://hal.archives-ouvertes.fr/hal-03631988
Contributor : Stéphane Popinet Connect in order to contact the contributor
Submitted on : Wednesday, April 6, 2022 - 9:17:11 AM
Last modification on : Tuesday, May 24, 2022 - 5:11:10 PM

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Wouter Mostert, Stéphane Popinet, Luc Deike. High-resolution direct simulation of deep water breaking waves: transition to turbulence, bubbles and droplets production. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2022, 942 (A27), ⟨10.1017/jfm.2022.330⟩. ⟨hal-03631988⟩

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