On Scale Modeling of Oil Droplet Formation from Spilled Oil

1991 ◽  
Vol 1991 (1) ◽  
pp. 501-506 ◽  
Author(s):  
Gerard A. L. Delvigne
Keyword(s):  
Complex Structure ◽  
Breaking Waves ◽  
Droplet Formation ◽  
Laboratory Model ◽  
Small Scale ◽  
Oil Droplets ◽  
Oil Droplet ◽  
Model Studies ◽  
Scale Modeling ◽  
Reliable Interpretation

ABSTRACT Oil droplets form through various processes when oil is spilled at sea:Breakup of the oil surface layer by breaking waves and intrusion of the droplets into the water column (natural dispersion)Enhanced breakup of the oil layer by application of dispersants (chemical dispersion)Breakup of oil lumps from a subsurface spill by turbulence in the waterEntrainment of droplets from a boomed oil slick caused by a large difference in velocity between the oil and the waterBreakup of oil droplets after disposal of oily water into the turbulent wake of a ship. The formation of droplets from a coherent oil mass has been found to be dependent on a complex structure of process parameters, for example, the turbulent eddy structure in the water, internal breaking waves on the oil-water interface, and viscosity and interfacial tension of the oil. The behavior of oil and oil droplet formation in the above processes can be studied relatively easily in small-scale laboratory models, provided that the scaling rules are understood and the laboratory results can be interpreted in terms of field situations. Several laboratory model studies of oil droplet formation were performed by Delft Hydraulics. Much attention was paid to scaling rules and the reliable interpretation of the results in terms of field conditions. Results and conclusions about the modeling process are discussed.

scholarly journals Small Scale Physical and Bio-Chemical Processes Affecting the Transport of Oil after a Spill

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Joseph Katz ◽  
CJ Beegle-Krause ◽  
Michel Boufadel ◽  
Marcelo Chamecki ◽  
Vijay John ◽  
...  
Keyword(s):  
Crude Oil ◽  
Size Distribution ◽  
Targeted Delivery ◽  
Breaking Waves ◽  
Halloysite Nanotubes ◽  
Small Scale ◽  
Oil Droplets ◽  
Form Complex ◽  
Oil Water ◽  
The Impact

Abstract A series of GOMRI-sponsored experimental and computational studies have discovered, elucidated and quantified the impact of small-scale processes on the dispersion, transport and weathering of crude oil slicks and subsurface plumes. Physical interfacial phenomena occurring at micron-scales include the formation of particle-stabilized emulsions, penetration of particles into oil droplets, formation of compound water-containing oil droplets during plume breakup, and the mechanisms affecting the breakup of oil into micro-droplet by tip streaming resulting from the drastic reduction in interfacial tension upon introduction of dispersant. Efforts aimed at development targeted delivery of surfactants have introduced solvent-free halloysite nanotubes that can be filled with surfactants, and preferentially released at oil-water interface. Buoyant surfactant-based gels, which enhance their encounter rates with oil slicks and adhere to weathered oil have also been developed. Studies of oil-bacteria interactions during early phases of biodegradation and shown how the bacteria, some highly active, attach to the oil-water interfaces and form complex films. Clay-decorated droplets sequester these bacteria and promote the propagation of these biofilm. Long extracellular polymeric substance (EPS) streamers generated by these biofilms form connected networks involving multiple droplets and debris, as well as increase the drag on the oil droplets. At 0.01–10 m scales, the generation of subsurface and airborne crude oil droplets by breaking waves, subsurface plumes and raindrop impact have been quantified. For waves, premixing the oil with dispersant reduces the droplets sizes to micron- and submicron-scales, and changes the slope of their size distribution. Without dispersant, the droplet diameters can be predicted based on the turbulence scales. With dispersant, the droplets are much smaller than the turbulence scales owing to the abovementioned tip-streaming. Aerosolization of oil is caused both by the initial splash and by subsequent bubble bursting, as entrained bubbles rise to the surface. Introduction of dispersant increases the airborne nano-droplet concentration by orders of magnitude, raising health questions. Dispersant injection also reduces the size of droplets in subsurface plumes, affecting the subsequent dispersion of these plume by currents and turbulence. Advancements have also been made in modeling of dissolution of oil in plumes, as well as in applications of Large Eddy Simulations (LES) to model plumes containing oil droplets and gas bubbles. The new multiscale framework, which accounts for the droplet size distribution and mass diffusion, can simulate the near- and far-fields of plumes, and predict the effect of vertical mixing promoted by turbulence on the transport of dispersed oil.

Modeling Oil Droplet Formation and Evolution under Breaking Waves

2009 ◽  
Vol 31 (5) ◽  
pp. 438-448 ◽  
Author(s):  
Z. Chen ◽  
C.-S. Zhan ◽  
K. Lee ◽  
Z.-K. Li ◽  
M. Boufadel
Keyword(s):  
Breaking Waves ◽  
Droplet Formation ◽  
Oil Droplet ◽  
Formation And Evolution

Numerical Simulation of Oil-Droplet Cleavage by Surfactant

1996 ◽  
Vol 118 (2) ◽  
pp. 201-209 ◽  
Author(s):  
Xiaoyi He ◽  
Micah Dembo
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Surface Tension ◽  
Large Deformation ◽  
Concentration Gradient ◽  
Surface Tension Gradient ◽  
Oil Droplets ◽  
Numerical Computations ◽  
Oil Droplet ◽  
Pure Surface

We present numerical computations of the deformation of an oil-droplet under the influence of a surface tension gradient generated by the surfactant released at the poles (the Greenspan experiment). We find this deformation to be very small under the pure surface tension gradient. To explain the large deformation of oil droplets observed in Greenspan’s experiments, we propose the existence of a phoretic force generated by the concentration gradient of the surfactant. We show that this hypothesis successfully explains the available experimental data and we propose some further tests.

scholarly journals Importance of Sub-Grid Scale Modeling for Accurate Aerodynamic Simulations

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Petter Ekman ◽  
James Venning ◽  
Torbjörn Virdung ◽  
Matts Karlsson
Keyword(s):  
The Body ◽  
Small Scale ◽  
Piv Measurements ◽  
Vortical Structures ◽  
Scale Modeling ◽  
Simple Geometry ◽  
Image Velocimetry ◽  
Large Eddy ◽  
Near Wall ◽  
Ahmed Body

Abstract The Ahmed body is one of the most well-investigated vehicle bodies for aerodynamic purposes. Despite its simple geometry, the flow around the body, especially at the rear, is very complex as it is dominated by a large wake with strong interaction between vortical structures. In this study, the flow around the 25 deg Ahmed body has been investigated using large eddy simulations and compared to high-resolution particle image velocimetry (PIV) measurements. Special emphasis was put on studying three commonly used sub-grid scale (SGS) models and their ability to capture vortical structures around the Ahmed body. The ability of the SGS models to capture the near-wall behavior and small-scale dissipation is crucial for capturing the correct flow field. Very good agreement between simulations and PIV measurements were seen when using the dynamic Smagorinsky-Lilly and the wall-adopting local eddy-viscosity SGS models, respectively. However, the standard Smagorinsky-Lilly model was not able to capture the flow patterns when compared to the PIV measurements due to shortcomings in the near-wall modeling in the standard Smagorinsky-Lilly model, resulting in overpredicted separation.

Visual pigments and oil droplets in diurnal lizards

2002 ◽  
Vol 205 (7) ◽  
pp. 927-938 ◽  
Author(s):  
Ellis R. Loew ◽  
Leo J. Fleishman ◽  
Russell G. Foster ◽  
Ignacio Provencio
Keyword(s):  
Visual Pigment ◽  
Visual Pigments ◽  
Anolis Carolinensis ◽  
Visual Cell ◽  
Oil Droplets ◽  
Oil Droplet ◽  
Long Wavelength ◽  
Apparent Color ◽  
Vitamin A2 ◽  
Insight Into

SUMMARY We report microspectrophotometric (MSP) data for the visual pigments and oil droplets of 17 species of Caribbean anoline lizard known to live in differing photic habitats and having distinctly different dewlap colors. The outgroup Polychrus marmoratus was also examined to gain insight into the ancestral condition. Except for Anolis carolinensis, which is known to use vitamin A2 as its visual pigment chromophore, all anoline species examined possessed at least four vitamin-A1-based visual pigments with maximum absorbance (λmax) at 564, 495,455 and 365 nm. To the previously reported visual pigments for A. carolinensis we add an ultraviolet-sensitive one withλ max at 365 nm. Five common classes of oil droplet were measured, named according to apparent color and associated with specific cone classes — yellow and green in long-wavelength-sensitive (LWS) cones,green only in medium-wavelength-sensitive (MWS) cones and colorless in short-wavelength-sensitive (SWS) and ultraviolet-sensitive (UVS) cones. MSP data showed that the colorless droplet in the SWS cone had significant absorption between 350 and 400 nm, while the colorless droplet in the UVS cone did not. The pattern for Polychrus marmoratus was identical to that for the anoles except for the presence of a previously undescribed visual cell with a rod-like outer segment, a visual pigment with a λmaxof 497 nm and a colorless oil droplet like that in the UVS cones. These findings suggest that anoline visual pigments, as far as they determine visual system spectral sensitivity, are not necessarily adapted to the photic environment or to the color of significant visual targets (e.g. dewlaps).

Visual pigments, oil droplets and cone photoreceptor distribution in the european starling (Sturnus vulgaris)

1998 ◽  
Vol 201 (9) ◽  
pp. 1433-1446 ◽  
Author(s):  
N S Hart ◽  
J C Partridge ◽  
I C Cuthill
Keyword(s):  
Visual Pigment ◽  
Sturnus Vulgaris ◽  
European Starling ◽  
Visual Pigments ◽  
Double Cone ◽  
Temporal Region ◽  
Oil Droplets ◽  
Tetrazolium Chloride ◽  
Oil Droplet ◽  
Single Cone

Microspectrophotometric measurements of retinal photoreceptors from the European starling (Sturnus vulgaris) revealed four classes of single cone, containing visual pigments with wavelengths of maximum absorbance (<IMG src="/images/symbols/lambda.gif" WIDTH="8" HEIGHT="12" ALIGN="BOTTOM" NATURALSIZEFLAG= "3">max) at 563, 504, 449 and close to 362 nm. The two longer-wave-sensitive single cones contained brightly coloured oil droplets which cut off light below 572 and 514 nm, respectively. The 449 nm <IMG src="/images/symbols/lambda.gif" WIDTH="8" HEIGHT="12" ALIGN="BOTTOM" NATURALSIZEFLAG="3">max pigment was associated with a 'colourless' oil droplet with peak measured absorptance below 400 nm. The ultraviolet-sensitive visual pigment was paired with a transparent oil droplet which showed no significant absorption above 350 nm. A single class of double cone was identified, both members of which contained the longwave-sensitive (<IMG src="/images/symbols/lambda.gif" WIDTH="8" HEIGHT= "12" ALIGN="BOTTOM" NATURALSIZEFLAG="3">max 563 nm) visual pigment. The principal member of the double cone contained an oil droplet with a topographically variable cut-off wavelength below 471 nm; the oil droplet found in the accessory member was only measured in the ventral retina and displayed three distinct peaks of absorption at approximately 430, 450 and 480 nm. Rod photoreceptors had a <IMG src="/images/symbols/lambda.gif" WIDTH="8" HEIGHT="12" ALIGN="BOTTOM" NATURALSIZEFLAG="3">max at 503 nm. A new polynomial for fitting visual pigment templates to ultraviolet-sensitive visual pigment data is given. Topographic density measurements of the different cone classes were made using Nitroblue-tetrazolium chloride to label selectively bleached photoreceptors. The two classes of shortwave-sensitive single cone were more abundant in the dorsal retina, and longwave-sensitive single cones were notably less abundant in the dorso-temporal region of the retina, which subserves binocular vision.

scholarly journals Emulsification of Surfactant on Oil Droplets by Molecular Dynamics Simulation

Molecules ◽  
2020 ◽  
Vol 25 (13) ◽  
pp. 3008
Author(s):  
Yaoshuang Cheng ◽  
Shiling Yuan
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Heavy Oil ◽  
Molecular Level ◽  
Sodium Dodecyl ◽  
Mean Square Displacement ◽  
Dynamics Simulation ◽  
Oil Droplets ◽  
Hydration Layer ◽  
Oil Droplet

Heavy oil in crude oil flooding is extremely difficult to extract due to its high viscosity and poor fluidity. In this paper, molecular dynamics simulation was used to study the emulsification behavior of sodium dodecyl sulfonate (SDSn) micelles on heavy oil droplets composed of asphaltenes (ASP) at the molecular level. Some analyzed techniques were used including root mean square displacement, hydrophile-hydrophobic area of an oil droplet, potential of mean force, and the number of hydrogen bonds between oil droplet and water phase. The simulated results showed that the asphaltene with carboxylate groups significantly enhances the hydration layer on the surface of oil droplets, and SDSn molecules can change the strength of the hydration layer around the surface of the oil droplets. The water bridge structure between both polar heads of the surfactant was commonly formed around the hydration layer of the emulsified oil droplet. During the emulsification of heavy oil, the ratio of hydrophilic hydrophobic surface area around an oil droplet is essential. Molecular dynamics method can be considered as a helpful tool for experimental techniques at the molecular level.

scholarly journals Scale Modeling of Snow–Avalanche Impact on Structures

1980 ◽  
Vol 26 (94) ◽  
pp. 189-196
Author(s):  
T. E. Lang ◽  
J.D. Dent
Keyword(s):  
Froude Number ◽  
Computer Modeling ◽  
Snow Avalanche ◽  
Small Scale ◽  
Snow Avalanches ◽  
Scale Modeling ◽  
Impact Processes ◽  
Model Fluid ◽  
Impact Predictions

AbstractSmall–scale modeling of flow and impact of snow avalanches is demonstrated to be both feasible and accurate. Geometric, kinematic, and force variables are scaled correctly under equivalence of Froude number between prototype and model using sifted snow as the model fluid. Physical and computer–simulated impact processes show correspondence, so that computer modeling is demonstrated to be a viable tool in flow and impact predictions.

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