Size Distribution and Dispersion of Droplets Generated by Impingement of Breaking Waves on Oil Slicks

Li, Cheng; Miller, Jerry L.; Wang, J.; Koley, Subhra Shankha; Katz, Joseph

doi:10.1002/2017jc013193

Cited by 102 publications

(127 citation statements)

References 91 publications

(111 reference statements)

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“…Li, Spaulding, et al (2017), similar in concept to that of Johansen et al (2015) and the work by Zeinstra-Helfrich et al (2017). Recently, C. Li, Miller, et al (2017) reported experimental results of oil dispersion due to a plunging breaker of a solitary wave without and with dispersant. Their results indicated that in the absence of dispersant, the DS model holds well for entrained droplets whose diameters are smaller than 70 μm but that it overestimates the number of submerged larger diameter droplets.…”

Section: Introductionsupporting

confidence: 63%

Oil Droplets Transport Under a Deep‐Water Plunging Breaker: Impact of Droplet Inertia

et al. 2018

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Oil droplets transport in a deep‐water plunging breaker of height 0.18 m was simulated by coupling computational fluid dynamics with Lagrangian particle tracking. The Reynolds‐averaged Navier‐Stokes equations were solved in a two‐dimensional vertical slice within the computational fluid dynamics code Fluent to reproduce the movement of breaking waves in the absence of wind stress and large‐scale turbulence. The generated plunging breaker generated two additional (residual) breakers, consistent with experimental observations from the literature. The hydrodynamics of the breaker was subsequently used as input to the Lagrangian particle tracking code, NEMO3D, where the equation of motion was solved for each droplet by incorporating the major local forces including those due to the mass of the droplet. The droplet sizes were selected to vary from 100 to 600 μm. It was found that the droplet plume split into three clouds, one below and upstream of the first breaker, one below the second breaker, and one downstream of the third breaker. The largest penetration depth was within the second cloud. The largest entrainment (fraction of surface mass in the water column) occurred for the 100‐μm droplets, while the smallest entrainment occurred for the 600 μm. However, the 300 μm exhibited smaller entrainment than smaller droplets, which is due to the vortical nature of the breaker, which advected the 300 μm horizontally and then upward. This has implications on the biodegradation and dissolution of droplets of various sizes, and on the application of countermeasures such as dispersant.

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Section: Introductionsupporting

confidence: 63%

Oil Droplets Transport Under a Deep‐Water Plunging Breaker: Impact of Droplet Inertia

et al. 2018

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“…As shown by Li et al (2017), the time evolution of the droplet size distribution at the measurement location could be represented well by a simple model that includes the effects of turbulent diffusion and droplet buoyancy only. Since the dissipation rate was quite low at the measurement location, Li et al (2017) neglected the effect of droplet breakup in their model. Consequently, for the case of crude oil with dispersants, the model under-predicted the number of smaller size droplets generated.…”

Section: Model For Breakup Frequencymentioning

confidence: 99%

“…The Weber number (W e = 2ρ(ǫd) 2/3 d/σ) based on the droplet diameter for the case with dispersants is approximately W e = 3, confirming that the effects of droplet breakup are important. Our goal is to expand the model of Li et al (2017) by including breakup and select a value of K * that can achieve improved agreement with their experimental data.…”

Section: Model For Breakup Frequencymentioning

confidence: 99%

A population balance model for large eddy simulation of polydisperse droplet evolution

et al. 2019

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In the context of many applications of turbulent multi-phase flows, knowledge of the dispersed phase size distribution and its evolution is critical to predicting important macroscopic features. We develop a large eddy simulation (LES) model that can predict the turbulent transport and evolution of size distributions, for a specific subset of applications in which the dispersed phase can be assumed to consist of spherical droplets, and occurring at low volume fraction. We use a population dynamics model for polydisperse droplet distributions specifically adapted to a LES framework including a model for droplet breakup due to turbulence, neglecting coalescence consistent with the assumed small dispersed phase volume fractions. We model the number density fields using an Eulerian approach for each bin of the discretized droplet size distribution. Following earlier methods used in the Reynolds averaged Navier-Stokes framework, the droplet breakup due to turbulent fluctuations is modelled by treating droplet-eddy collisions as in kinetic theory of gases. Existing models assume the scale of droplet-eddy collision to be in the inertial range of turbulence. In order to also model smaller droplets comparable to or smaller than the Kolmogorov scale we extend the breakup kernels using a structure function model that smoothly transitions from the inertial to the viscous range. The model includes a dimensionless coefficient that is fitted by comparing predictions in a one-dimensional version of the model with a laboratory experiment of oil droplet breakup below breaking waves. After initial comparisons of the one-dimensional model to measurements of oil droplets in an axisymmetric jet, it is then applied in a threedimensional LES of a jet in crossflow with large oil droplets of a single size being released at the source of the jet. We model the concentration fields using N d = 15 bins of discrete droplet sizes and solve scalar transport equations for each bin. The resulting droplet size distributions are compared with published experimental data, and good agreement for the relative size distribution is obtained. The LES results also enable us to quantify size distribution variability. We find that the probability distribution functions of key quantities such as the total surface area and the Sauter mean diameter of oil droplets are highly variable, some displaying strong non-Gaussian intermittent behavior.

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“…Due to the difficulty of reproducing air entrainment from breaking waves in small-scale laboratory systems, researchers have used different experimental setups to generate subsurface bubbles including porous glass tubes (Mårtensson et al, 2003;Scott, 1975), overturning buckets (Carey et al, 1993;Haines & Johnson, 1995), continuous jets (May et al, 2016;Salter et al, 2014), intermittent water sheets (Stokes et al, 2013(Stokes et al, , 2016, and wave channels (Deane & Stokes, 2002;Li et al, 2017;Loewen et al, 1996). The validity of such setups to faithfully reproduce air-water interactions from breaking waves depends on their ability to replicate the in situ bubbles and aerosols size distributions (Fuentes et al, 2010;Stokes et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

A Systematic Analysis of the Salinity Effect on Air Bubbles Evolution: Laboratory Experiments in a Breaking Wave Analog

Harb

Foroutan

2019

JGR Oceans

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The evolution of air bubbles after breaking waves plays an important role in gas and particle exchange between water bodies and the atmosphere. To improve our understanding of the impacts of salinity on this process, we systematically investigate the effect of salt concentrations ranging from 0 to 40 g/kg on the volume and size distributions of subsurface bubble plumes and surface foams in a laboratory breaking wave analog. Our experimental setup utilizes an intermittent plunging sheet to simulate breaking waves, while two synchronized digital cameras were used to monitor the temporal evolution of bubble plumes and surface foams. We first highlight the importance of plunging sheet intermittency on surface foam evolution. We then show that increasing salinity enhances the entrainment of submillimeter bubbles but has a less significant effect on larger supramillimeter bubbles. We observed that the foam area in saltier waters is consistently higher than that in freshwater throughout the foam decay phase. Furthermore, our investigation of surface bubble sizes shows that salinity has a more distinct effect on smaller (sub 2 mm) than on larger bubbles. This suggests that salinity may have a more pronounced impact on jet than on film drops ejection mechanisms. Finally, we conclude that the change in salinity within the typical oceanographic range is likely not a major factor for bubble-mediated interactions at the water surface during breaking waves. However, even low-salt concentrations greatly alter air entrainment characteristics in freshwater systems. Plain Language SummaryWhen sea waves break, they entrain large volumes of air in the form of bubbles. These bubbles rise up to the surface and burst, ejecting gas and small droplets into the air. This ejection mechanism plays an important role in air quality and climate dynamics. The effect of water salinity on this process is still not well understood. We used an intermittent plunging waterfall inside a laboratory tank and digital cameras to monitor the evolution of bubbles within and at the surface of water. We found that the jet intermittency affects the foam evolution on the surface following the wave-breaking event. Increasing water salinity led to an increase in the entrained bubbles number, and potentially the air volume injected by the breaking waves. We also observed a larger and more persistent foam patch in more saline water than in freshwater. The size of the surface bubbles in the foam patch was also affected by the salinity indicating that the latter affects the bubble-bursting mechanism on the surface. We conclude that water salinity has a measurable effect on the air volume and bubble sizes injected by breaking waves and should be accounted for in future air-sea interactions studies.

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Size Distribution and Dispersion of Droplets Generated by Impingement of Breaking Waves on Oil Slicks

Cited by 102 publications

References 91 publications

Oil Droplets Transport Under a Deep‐Water Plunging Breaker: Impact of Droplet Inertia

Oil Droplets Transport Under a Deep‐Water Plunging Breaker: Impact of Droplet Inertia

A population balance model for large eddy simulation of polydisperse droplet evolution

A Systematic Analysis of the Salinity Effect on Air Bubbles Evolution: Laboratory Experiments in a Breaking Wave Analog

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