Three‐Dimensional Measurements of Air Entrainment and Enhanced Bubble Transport During Wave Breaking

Ruth, Daniel; Néel, B.; Erinin, Martin A.; Mazzatenta, Megan; Jaquette, Robert; Véron, Fabrice; Deike, Luc

doi:10.1029/2022gl099436

Cited by 4 publications

(1 citation statement)

References 33 publications

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“…Bubbles on the ocean are created by breaking waves as air is entrained under the surface. The characteristic depth of bubble entrainment has been found to scale with the significant wave height,

( 62–65 ) so that we consider the height over which the bubbles are rising

2

. While there are multiple mechanisms which disperse microplastic in the ocean ( 66 ), the turbulent velocity field created by breaking waves—which entrain air to create bubbles—extends with the significant wave height ( 67 ), so we consider that the microplastic layer can be written as

2

.…”

Section: Modeling Global Emission Of Oceanic Microplasticmentioning

confidence: 99%

Ocean emission of microplastic

Shaw,

Li,

Nunes

et al. 2023

PNAS Nexus

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Microplastics are globally ubiquitous in marine environments, and their concentration is expected to continue rising at significant rates as a result of human activity. They present a major ecological problem with well-documented environmental harm. Sea spray from bubble bursting can transport salt and biological material from the ocean into the atmosphere, and there is a need to quantify the amount of microplastic that can be emitted from the ocean by this mechanism. We present a mechanistic study of bursting bubbles transporting microplastics. We demonstrate and quantify that jet drops are efficient at emitting microplastics up to 280μm in diameter and are thus expected to dominate the emitted mass of microplastic. The results are integrated to provide a global microplastic emission model which depends on bubble scavenging and bursting physics; local wind and sea state; and oceanic microplastic concentration. We test multiple possible microplastic concentration maps to find annual emissions ranging from 0.02 to 7.4—with a best guess of 0.1—mega metric tons per year and demonstrate that while we significantly reduce the uncertainty associated with the bursting physics, the limited knowledge and measurements on the mass concentration and size distribution of microplastic at the ocean surface leaves large uncertainties on the amount of microplastic ejected.

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( 62–65 ) so that we consider the height over which the bubbles are rising

2

2

.…”

Section: Modeling Global Emission Of Oceanic Microplasticmentioning

confidence: 99%

Ocean emission of microplastic

Shaw,

Li,

Nunes

et al. 2023

PNAS Nexus

Self Cite

View full text Add to dashboard Cite

show abstract

Comparison between shadow imaging and in-line holography for measuring droplet size distributions

et al. 2023

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A direct comparison of the droplet size and number measurements using in-line holography and shadow imaging is presented in three dynamically evolving laboratory scale experiments. The two experimental techniques and image processing algorithms used to measure droplet number and radii are described in detail. Droplet radii as low as $$r = 14$$ r = 14 µm are measured using in-line holography and $$r = 50$$ r = 50 µm using shadow imaging. The droplet radius measurement error is estimated using a calibration target (reticle) and it was found that the holographic technique is able to measure droplet radii more accurately than shadow imaging for droplets with $$r \le 625$$ r ≤ 625 µm. Using the measurements of droplet number and size we quantitatively cross-validate and assess the accuracy of the two measurement techniques. The droplet size distributions, N(r), are measured in all three experiments and are found to agree well between the two measurement techniques. In one of the laboratory experiments, simultaneous measurements of droplets ($$r \ge 14$$ r ≥ 14 µm, using holography) and dry aerosols ($$0.07 \lessapprox r \lessapprox 2$$ 0.07 ⪅ r ⪅ 2 µm, using an scanning mobility particle sizer and $$0.15 \lessapprox r \lessapprox 5$$ 0.15 ⪅ r ⪅ 5 µm using an optical particle sizer) are reported, one of the first such comparison to the best of our knowledge. The total number and volume of droplets is found to agree well between both techniques in the three experiments. We demonstrate that a relatively simple shadow imaging technique can be just as reliable when compared to a more sophisticated holographic measurement technique over their common droplet radius measurement range. The agreement in results is shown to be valid over a large range of droplet concentrations, which include experiments with relatively sparse droplet concentrations as low as 0.02 droplets per image. Advantages and disadvantages for the two techniques are discussed in the context of our results. The main advantages to in-line holography are the greater accuracy in droplet radius measurement, greater spatial resolution, larger depth of field, and the high repetition rate and short pulse duration of the laser light source. In comparison, the main advantages to shadow imaging are the simpler experimental setup, image processing algorithm, and fewer computer resources necessary for image processing. Droplet statistics like number and size are found to be very reliable between the two methods for large range of droplet densities, $${\mathcal {P}}_{r>50}$$ P r > 50 , ranging from $$10^{-4} \le {\mathcal {P}}_{r>50} \le 10^{-1}$$ 10 - 4 ≤ P r > 50 ≤ 10 - 1 cm$$^{-3}$$ - 3 , when the two techniques are implemented as shown in this paper.

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A data-driven approach to analyze bubble deformation in turbulence

Calado,

Capuano,

Balaras

2024

Physics of Fluids

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Bubble deformation and breakup from turbulence is present in many engineering applications and in nature, yet the physical mechanisms still remain poorly understood. Depending on the local turbulence intensity or Weber number, a bubble may either deform without breakup, suffer a violent breakup, or exhibit a resonant behavior, where the turbulent eddies excite the bubble's natural frequencies. Recent studies have used spherical harmonic decomposition to analyze bubble interaction with turbulence, quantifying the deformation energy of each eigenmode. However, this approach is only applicable for small levels of deformation (linear regime), while the bubble shape remains close to a sphere. In the present work, we present a novel data-driven approach combining large deformation diffeomorphic metric mapping and proper orthogonal decomposition, which is more robust for large deformations. The method is tested on a set of validation cases and applied to turbulent bubble deformation cases obtained from direct numerical simulations data.

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Three‐Dimensional Measurements of Air Entrainment and Enhanced Bubble Transport During Wave Breaking

Cited by 4 publications

References 33 publications

Ocean emission of microplastic

Ocean emission of microplastic

Comparison between shadow imaging and in-line holography for measuring droplet size distributions

A data-driven approach to analyze bubble deformation in turbulence

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