scholarly journals Marangoni instabilities of drops of different viscosities in stratified liquids

2021 ◽  
Vol 932 ◽  
Author(s):  
Yanshen Li ◽  
Jochem G. Meijer ◽  
Detlef Lohse
Keyword(s):  
Concentration Gradient ◽  
Concentration Field ◽  
Gravitational Effect ◽  
Oscillatory Instability ◽  
Scaling Theory ◽  
Limiting Factor ◽  
Gravitational Acceleration ◽  
Water Mixture ◽  
Marangoni Flow ◽  
Drop Radius

For an immiscible oil drop immersed in a stably stratified ethanol–water mixture, a downwards solutal Marangoni flow is generated on the surface of the drop, owing to the concentration gradient, and the resulting propulsion competes against the downwards gravitational acceleration of the heavy drop. In prior work of Li et al. (Phys. Rev. Lett., vol. 126, issue 12, 2021, 124502), we found that for drops of low viscosity, an oscillatory instability of the Marangoni flow is triggered once the Marangoni advection is too strong for diffusion to restore the stratified concentration field around the drop. Here we experimentally explore the parameter space of the concentration gradient and drop radius for high oil viscosities and find a different and new mechanism for triggering the oscillatory instability in which diffusion is no longer the limiting factor. For such drops of higher viscosities, the instability is triggered when the gravitational effect is too strong so that the viscous stress cannot maintain a stable Marangoni flow. This leads to a critical drop radius above which the equilibrium is always unstable. Subsequently, a unifying scaling theory that includes both the mechanisms for low and for high viscosities of the oil drops is developed. The transition between the two mechanisms is found to be controlled by two length scales: the drop radius $R$ and the boundary layer thickness $\delta$ of the Marangoni flow around the drop. The instability is dominated by diffusion for $\delta < R$ and by viscosity for $R<\delta$ . The experimental results for various drops of different viscosities can well be described with this unifying scaling theory. Our theoretical description thus provides a unifying view of physicochemical hydrodynamic problems in which the Marangoni stress is competing with a stable stratification.

THE EFFECTS OF ELASTIC STIFFENING ON THE EVOLUTION OF THE STRESS FIELD WITHIN A SPHERICAL ELECTRODE PARTICLE OF LITHIUM-ION BATTERIES

2013 ◽  
Vol 05 (04) ◽  
pp. 1350040 ◽  
Author(s):  
WENBIN ZHOU ◽  
FENG HAO ◽  
DAINING FANG
Keyword(s):  
Stress Field ◽  
Lithium Ion Batteries ◽  
Internal Stress ◽  
Concentration Gradient ◽  
Concentration Field ◽  
Lithium Ion ◽  
Coupling Model ◽  
Ion Concentration ◽  
Hysteresis Phenomenon ◽  
Mechanical Coupling

Poor cyclic performance of lithium-ion batteries is calling for efforts to study its capacity attenuation mechanism. The internal stress field produced in the lithium-ion battery during its charging and discharging process is a major factor for its capacity attenuation, research on it appears especially important. We established an electrochemical –mechanical coupling model with the consideration of the influence of elastic stiffening on diffusion for graphite anode materials. The results show that the inner stress field strongly depends on the lithium-ion concentration field, greater concentration gradients lead to greater stresses. The evolution of the stress field is similar to that of the concentration gradient but lags behind it, which shows hysteresis phenomenon. Elastic stiffening can lower the concentration gradient and increase elastic modulus, which are two major factors influencing the inner stress field. We conclude that the latter is more dominant compared to the former, and elastic stiffening acts to increasing the internal stress.

scholarly journals Superspreading on Hydrophobic Substrates: Effect of Glycerol Additive

2019 ◽  
Vol 3 (2) ◽  
pp. 51 ◽  
Author(s):  
Nina M. Kovalchuk ◽  
Jacques Dunn ◽  
Jack Davies ◽  
Mark J. H. Simmons
Keyword(s):  
Silicone Oil ◽  
Water Mixture ◽  
Marangoni Flow ◽  
Glycerol Content ◽  
Complete Wetting ◽  
Glycerol Water ◽  
Left Behind ◽  
Surfactant Solutions ◽  
Trisiloxane Surfactants ◽  
Equilibration Rate

The spreading of solutions of three trisiloxane surfactants on two hydrophobic substrates, polyethylene and polyvinylidenefluoride, was studied with the addition of 0–40 mass % of glycerol. It was found that all the surfactant solutions spread faster than silicone oil of the same viscosity, confirming the existence of a mechanism which accelerates the spreading of the surfactant solutions. For the non-superspreading surfactant, BT-233, addition of glycerol improved the spreading performance on polyvinylidenefluoride and resulted in a transition from partial to complete wetting on polyethylene. The fastest spreading was observed for BT-233 at a concentration of 2.5 g/L, independent of glycerol content. For the superspreading surfactants, BT-240 and BT-278, the concentration at which the fastest spreading occurs systematically increased with concentration of glycerol on both substrates from 1.25 g/L for solutions in water to 10 g/L for solutions in 40% glycerol/water mixture. Thus, the surfactant equilibration rate (and therefore formation of surface tension gradients) and Marangoni flow are important components of a superspreading mechanism. De-wetting of the solutions containing glycerol, once spread on the substrates, resulted in the formation of circular drop patterns. This is in contrast to the solely aqueous solutions where the spread film shrank due to evaporation, without any visible traces being left behind.

scholarly journals A new program for the hydraulic calculation of steam-water mixture pipelines in geothermal fields

2020 ◽  
Vol 192 ◽  
pp. 04004
Author(s):  
Aleksandr Shulyupin ◽  
Alla Chermoshentseva ◽  
Natalia Varlamova
Keyword(s):  
Gravitational Effect ◽  
Water Velocity ◽  
Hydraulic Calculation ◽  
Water Mixture ◽  
Two Phase ◽  
Drift Model ◽  
Geothermal Fields ◽  
Proposed Model ◽  
Empirical Coefficients ◽  
Positive Results

A new mathematical model of steam-water flow in a pipeline, which takes into account the gravitational effect and satisfies new challenges in the development of geothermal fields with two-phase transportation of the heat carrier is presented. Taking into account the gravitational effect in the upstream flows, a method based on the “drift model”, which determines the steam velocity averaged over the crosssection was used. A similar method is proposed for downstream flows, but it determines the water velocity averaged over the cross-section. In this case, analogs of empirical coefficients were used. These coefficients determined from the condition of equality of parameters calculated using different approaches in a horizontal flow. The model was verified, which showed positive results. The proposed model significantly expands the possibilities of hydraulic calculation of steam-water mixture pipelines in geothermal fields.

scholarly journals Quantumbit Cosmology Explains Effects of Rotation Curves of Galaxies

2021 ◽  
Author(s):  
Thomas Görnitz ◽  
Uwe Schomäcker
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Gravitational Effect ◽  
Big Bang ◽  
Gravitational Acceleration ◽  
Rotation Curves ◽  
Effects Of Rotation ◽  
The Big Bang ◽  
Black Hole Masses ◽  
Absolute Quantum

AbstractSome terms identify enigmata of today’s cosmology: “Inflation” is expected to explain the homogeneity and isotropy of the cosmic background. The repulsive force of a “dark energy” shall prevent a re-collapse of the cosmos. The additional gravitational effect of a “dark matter” was originally supposed to explain the deviations of the rotation curves of the galaxies from Kepler’s laws. Adopting a theory founded on the core notion of absolute quantum information–Protyposis–being a cosmological concept from the outset, the observed phenomena can be explained without postulating further unknown specific “particles” or “fields”. Moreover, this theory allows for a rationalization of the fact that huge black holes with their enormous jet structures, acting as “seeds” of the galaxies, are detected ever closer to the big bang. The problem of the rotation curves in the galaxies can be addressed outside of General Relativity within a Newtonian approximation: by an attenuation of the gravitational acceleration as in the modified Newtonian dynamics, or by the effect of additional invisible “particles of dark matter”, yet unknown and not yet established in natural sciences. Within the Protyposis theory, these problems are solved without having to invent a lot of parameters. The cosmology of the Protyposis causes the change of the gravitational acceleration in the vicinity of large (black hole) masses and, at the same time, avoids a recollapse of the cosmos for which a cosmological constant or “dark energy” was invented.

Instantaneous three-dimensional concentration measurements in the self-similar region of a round high-Schmidt-number jet

1994 ◽  
Vol 279 ◽  
pp. 313-350 ◽  
Author(s):  
M. Yoda ◽  
L. Hesselink ◽  
M. G. Mungal
Keyword(s):  
Concentration Gradient ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Concentration Field ◽  
The Self ◽  
Gradient Field ◽  
Geometrical Parameters ◽  
Similar Region ◽  
Self Similar ◽  
Local Topology

The virtually instantaneous three-dimensional concentration fields in the self-similar region of natural or unexcited, circularly excited and weakly buoyant round jets of Reynolds number based on nozzle diameter of 1000 to 4000 are measured experimentally at a spatial resolution of the order of the Kolmogorov length scale. Isoconcentration surfaces are extracted from the concentration field. These surfaces along with their geometrical parameters are used to deduce the structure and modal composition of the jet. The concentration gradient field is calculated, and its local topology is classified using critical-point concepts.Large-scale structure is evident in the form of ‘clumps’ of higher-concentration jet fluid. The structure, which has a downstream extent of about the local jet diameter, is roughly axisymmetric with a conical downstream end. This structure appears to be present only in fully turbulent jets. The antisymmetric two-dimensional images previously thought to be axial slices of an expanding spiral turn out in our data to instead be slices of a simple sinusoid in three dimensions. This result suggests that the helical mode, when present, is in the form of a pair of counter-rotating spirals, or that the +1 and −1 modes are simultaneously present in the flow, with their relative phase set by initial conditions.In terms of local structure, regions with a large magnitude in concentration gradient are shown to have a local topology which is roughly axisymmetric and compressed along the axis of symmetry. Such regions, which would be locally planar and sheet-like, may correspond to the superposition of several of the layer-like structures which are the basic structure of the fine-scale passive scalar field (Buch & Dahm 1991; Ruetsch & Maxey 1991).

scholarly journals Thermally driven Marangoni surfers

2014 ◽  
Vol 752 ◽  
pp. 589-601 ◽  
Author(s):  
Alois Würger
Keyword(s):  
Long Range ◽  
Short Range ◽  
Dipole Moments ◽  
Particle Surface ◽  
Concentration Field ◽  
The Self ◽  
The Other ◽  
Marangoni Flow ◽  
Thermally Driven ◽  
Stress Discontinuity

AbstractWe study autopropulsion of an interface particle that is driven by the Marangoni stress arising from a self-generated asymmetric temperature or concentration field. We calculate separately the long-range Marangoni flow $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}{\boldsymbol {v}}^{I}$ due to the stress discontinuity at the interface and the short-range velocity field ${\boldsymbol {v}}^{P}$ imposed by the no-slip condition on the particle surface. Both contributions are evaluated for a spherical floater with temperature monopole and dipole moments. We find that the self-propulsion velocity is given by the amplitude of the ‘source doublet’ that belongs to the short-range contribution ${\boldsymbol {v}}^{P}$. Hydrodynamic interactions, on the other hand, are determined by the long-range Marangoni flow ${\boldsymbol {v}}^{I}$. Its dipolar part results in an asymmetric advection pattern of neighbouring particles, which in turn may perturb the known hexatic lattice or even favour disordered states.

Survival of organic compounds in ejecta from hypervelocity impacts on ice

2009 ◽  
Vol 8 (1) ◽  
pp. 19-25 ◽  
Author(s):  
S.A. Bowden ◽  
J. Parnell ◽  
M.J. Burchell
Keyword(s):  
Stearic Acid ◽  
Organic Compounds ◽  
Concentration Gradient ◽  
Organic Molecules ◽  
Water Mixture ◽  
Hypervelocity Impacts ◽  
Surface Materials ◽  
Icy Bodies ◽  
The Impact ◽  
Β Carotene

AbstractHypervelocity impacts (HVIs) where organic-bearing ice constitutes the target material are important in several aspects of planetary and space science: (1) sampling of planetary surfaces using a hypervelocity projectile to impact the surface and eject surface materials for measurement or collection by a spacecraft; (2) the transfer of organic material between planetary bodies; and (3) providing energy for chemical processes involving surface materials. While small organic molecules (~6 carbon atoms), if present in surface materials, will likely be present in HVI-ejecta, uncertainty remains for larger organic molecules. It is the larger molecular weight compounds which could constitute direct evidence of life, and thus their survival within an HVI-ejecta plume is of key importance when evaluating strategies for life detection on icy bodies. It is not currently known what large organic molecules, and in what concentrations, may be present on icy bodies in the Solar System, but it is highly likely some will be more chemically stable during a HVI than others. Accordingly, in this study we examined a range of chemicals (β,β carotene, stearic acid and anthracene) with molecular weights between 178 and 536 daltons, and three different types of chemical structure. The compounds were solvated in a dimethylsulfoxide/water mixture and frozen. The frozen targets were impacted with steel spheres 1 and 1.5 mm in diameter at velocities of about 4.9 km s−1. Ice ejected during the impact was collected and underwent chemical analysis. The most labile compound (β,β carotene) was only detected (in small amounts) in the ejecta (and only that emitted at the lowest angles of ejection), although the other compounds were present in larger quantities and at a range of ejection angles. A concentration gradient was observed within the ejecta as a function of angle of ejection. This was not the same for both stearic acid and anthracene: the greatest concentrations of stearic acid were found at shallow angles of ejection whereas anthracene was most abundant at both intermediate and large angles of ejection, implying an inverted concentration gradient. These observations may indicate that organic compounds are variably altered and destroyed during a HVI with ice and that the ejecta plume does not sample the original materials equally at all angles of ejection. Future work is planned and will evaluate fractional survival for a greater range of compound types, impact materials and velocities.

Traveling-wave convection in a narrow rectangular cell

1992 ◽  
Vol 70 (9) ◽  
pp. 689-695 ◽  
Author(s):  
Minghui Liu ◽  
John R. de Bruyn
Keyword(s):  
Aspect Ratio ◽  
Flow Visualization ◽  
Traveling Wave ◽  
Concentration Field ◽  
Numerical Calculations ◽  
Water Mixture ◽  
Rectangular Cell ◽  
Constrained Geometry

Traveling-wave convection in an ethanol–water mixture confined in a narrow rectangular cell of height:width aspect ratio 1:0.3 is studied using shadowgraph flow visualization. We are able to identify qualitatively the contributions to the shadowgraph intensity due to the concentration field in the convecting mixture. The measured shadowgraph intensities and traveling-wave frequencies share features with the results of numerical calculations, which assume an infinitely wide cell, and of experiments done in wider cells, but there are significant quantitative differences, apparently due to our highly constrained geometry.

scholarly journals Gravitational-Magnetic-Electric Interaction in Controlling Relative Permittivity and Permeability

2021 ◽  
Author(s):  
Yin Zhu
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Relative Permittivity ◽  
Gravitational Effect ◽  
Gravitational Acceleration ◽  
Field Interaction ◽  
The Earth ◽  
Electric Interaction ◽  
Permittivity And Permeability

Appling the controlling relative permittivity and permeability in the equations for the gravitational-magnetic-electric field interaction, a very large variation of the gravitational acceleration of the Earth by electric/magnetic field could be arrived at. This conclusion may be supported by some of the experiments for the gravitational effect of superconductivity.

scholarly journals The Role of Hydrogen Bonding in the Dehydration of Bioalcohols in Hydrophobic Pervaporation Membranes

2021 ◽  
Author(s):  
Rafael M. Madero-Castro ◽  
Sofía Calero ◽  
A. Ozgur Yazaydin
Keyword(s):  
Hydrogen Bonding ◽  
Concentration Gradient ◽  
Md Simulations ◽  
Single Component ◽  
Biofuel Production ◽  
Water Mixture ◽  
Oh Groups ◽  
Mixture Separation ◽  
Pervaporation Membrane ◽  
Alcohol Water

<p>The dehydration of bioalcohols is considered one of the major factors contributing to the cost of biofuel production. In this study, liquid phase separation of water from methanol and ethanol in a siliceous MFI pervaporation membrane was studied by performing concentration gradient driven molecular dynamic (CGD-MD) simulations. CGD-MD simulations work by imposing a higher concentration in the feed side and a lower concentration in the permeate side of the membrane. This creates a concentration gradient across the membrane that facilitates the diffusion of molecules from the feed to the permeate side, mimicking the experimental pervaporation membrane set up. Fluxes of methanol, ethanol and water were calculated in single component permeation simulations and in equimolar methanol-water and ethanol-water mixture separation simulations. It was found that water formed hydrogen bonding with the silanol (Si-OH) groups on the external surface of the MFI and did not enter the membrane in the single component permeation simulation. While this may suggest that MFI can be used to effectively dehydrate bioalcohols, our simulations showed that water permeated through the MFI membrane when it was in a mixture with either methanol or ethanol. Furthermore, in the alcohol-water mixture simulations, the fluxes of methanol and ethanol were significantly lower than that of expected based on their single component fluxes. A detailed analysis of hydrogen bonding in the alcohol-water mixture separation simulations revealed that water preferred making hydrogen bonds with methanol and ethanol rather than with the silanol groups. This resulted in drifting of water molecules along with permeating alcohol molecules in to the MFI membrane in mixture simulations, while slowing the permeation of methanol and ethanol fluxes. </p>

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