Measurements of Static and Dynamic Bubble Surface Tension Using a Deformation-Based Microfluidic Tensiometer

2021 ◽  
Author(s):  
Shihao Liu ◽  
Cari S. Dutcher
Keyword(s):  
Surface Tension ◽  
Bubble Surface

scholarly journals Application of Depletion Attraction in Mineral Flotation: II. Effects of Depletant Concentration

Minerals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 450 ◽  
Author(s):  
Gahee Kim ◽  
Junhyun Choi ◽  
Sowon Choi ◽  
KyuHan Kim ◽  
Yosep Han ◽  
...  
Keyword(s):  
Surface Tension ◽  
Polymer Brush ◽  
Bubble Surface ◽  
Mass Ratio ◽  
Attraction Force ◽  
Surface Acting ◽  
Pure Silica ◽  
Mineral Flotation ◽  
Air Water Interface ◽  
High Concentrations

Along with the accompanying theory article, we experimentally investigate the effect of the depletion attraction force on the flotation of malachite. While varying the concentration of the depletion agent (polyethylene glycol), three different systems are studied: pure malachite, pure silica and a 1:1 mass ratio of malachite and silica binary system. We find that the recovery increases significantly as the concentration of the depletion reagents increases for all three systems. However, the recovery suddenly decreases in a certain concentration range, which corresponds to the onset of the decreased surface tension when high concentrations of the depletion agent are used. The decreased surface tension of the air/water interface suggests that the recovery rate is lowered due to the adsorption of the depletion agent to the bubble surface, acting as a polymer brush. We also perform experiments in the presence of a small amount of a collector, sodium oleate. An extremely small amount of the collector (10−10–10−5 M) leads to the increase in the overall recovery, which eventually reaches nearly 100 percent. Nevertheless, the grade worsens as the depletant provides the force to silica particles as well as target malachite particles.

Effects of Phospholipid Layers on the Motion of Microbubbles Under Pressure Variations

2011 ◽  
Author(s):  
Yuki Tanaka ◽  
Hiroyuki Takahira
Keyword(s):  
Surface Tension ◽  
Phosphate Buffer Solution ◽  
Ccd Camera ◽  
Gas Diffusion ◽  
Bubble Surface ◽  
Gas Permeation ◽  
Experimental Result ◽  
Buffer Solution ◽  
Dynamic Surface ◽  
Instantaneous Increase

The shrinking and growth of microbubbles under pressure variations are observed with a CCD camera. The influence of gas diffusion on the stability of microbubbles covered with phospholipid layers is investigated. The microbubbles are made with acoustic liposomes encapsulating phosphate buffer solution and perfluoropropane gas. It is shown that when the ambient liquid pressure increases, the observed microbubbles shrink accompanied with the cyclic surface buckling and smoothing process. The bubble surface smoothing in the process shows that the excess phospholipid layers are removed from the surface, which results in the instantaneous bubble shrinkage. It is also shown that the smaller the initial radius is, the more the growth of microbubbles is reduced. The bubble model by Takahira and Ito, in which the dynamic surface tension and the gas permeation resistance of molecular layers are considered, is utilized to simulate the experiments. The simulation is in qualitative agreement with the experimental result except for the instantaneous bubble shrinkage. The model is improved so as to consider the instantaneous increase of surface tension. The instantaneous bubble shrinkage is simulated successfully with the improved model. The results suggest that the instantaneous increase of surface tension is caused by the shedding of the excess phospholipid layer material due to the zippering process proposed by Borden and Longo.

scholarly journals Bubble Rise Velocity and Surface Mobility in Aqueous Solutions of Sodium Dodecyl Sulphate and n-Propanol

Minerals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 743
Author(s):  
Pavlína Basařová ◽  
Yuliya Kryvel ◽  
Jakub Crha
Keyword(s):  
Surface Tension ◽  
Aqueous Solutions ◽  
Sodium Dodecyl Sulphate ◽  
Sodium Dodecyl ◽  
Bubble Surface ◽  
Rise Velocity ◽  
Bubble Rise ◽  
Spherical Bubble ◽  
Surface Mobility ◽  
Bubble Rise Velocity

Aqueous solutions of simple alcohols exhibit many anomalies, one of which is a change in the mobility of the bubble surface. This work aimed to determine the effect of the presence of another surface-active agent on bubble rise velocity and bubble surface mobility. The motion of the spherical bubble in an aqueous solution of n-propanol and sodium dodecyl sulphate (SDS) was monitored by a high-speed camera. At low alcohol concentrations (xP < 0.01), both the propanol and SDS molecules behaved as surfactants, the surface tension decreased and the bubble surface was immobile. The effect of the SDS diminished with increasing alcohol concentrations. In solutions with a high propanol content (xP > 0.1), the SDS molecules did not adsorb to the phase interface and thus, the surface tension of the solution was not reduced with the addition of SDS. Due to the rapid desorption of propanol molecules from the bottom of the bubble, a surface tension gradient was not formed. The drag coefficient can be calculated using formulas for the mobile surface of a spherical bubble.

The toroidal bubble

1968 ◽  
Vol 32 (1) ◽  
pp. 97-112 ◽  
Author(s):  
T. J. Pedley
Keyword(s):  
Surface Tension ◽  
Viscous Fluid ◽  
Energy Equation ◽  
Bubble Surface ◽  
Inviscid Fluid ◽  
Initial Instant ◽  
Bubble Volume ◽  
Toroidal Bubble ◽  
History Of ◽  
Impulse Equation

It has been observed by Walters & Davidson (1963) that release of a mass of gas in water sometimes produces a rising toroidal bubble. This paper is concerned with the history of such a bubble, given that at the initial instant the motion is irrotational everywhere in the water. The variation of its overall radius a with time may be predicted from the vertical impulse equation, and it should be possible to make the same prediction by equating the rate of loss of combined kinetic and potential energy to the rate of viscous dissipation. This is indeed seen to be the case, but not before it is recognized that in a viscous fluid vorticity will continually diffuse out from the bubble surface, destroying the irrotationality of the motion, and necessitating an examination of the distribution of vorticity. The impulse equation takes the same form as in an inviscid fluid, but the energy equation is severely modified. Other results include an evaluation of the effect of a hydrostatic variation in bubble volume, and a prediction of the time which will have elapsed before the bubble becomes unstable under the action of surface tension.

Deformation of a bubble or drop in a uniform flow

1980 ◽  
Vol 101 (4) ◽  
pp. 673-686 ◽  
Author(s):  
Jean-Marc Vanden-Broeck ◽  
Joseph B. Keller
Keyword(s):  
Surface Tension ◽  
Liquid Drop ◽  
Pressure Ratio ◽  
Bubble Surface ◽  
Stagnation Pressure ◽  
Two Dimensional ◽  
Bubble Shape ◽  
Fluid Density ◽  
Circular Arc ◽  
Steady Potential

Steady potential flow around a two-dimensional bubble with surface tension, either free or attached to a wall, is considered. The results also apply to a liquid drop. The flow and the bubble shape are determined as functions of the contact angle β and the dimensionless pressure ratio γ = (pb − ps)/½ρU2. Here pb is the pressure in the bubble, ps = p∞ + ½ρU2 is the stagnation pressure, p∞ is the pressure at infinity, ρ is the fluid density and U is the velocity at infinity. The surface tension σ determines the dimensions of the bubble, which are proportional to 2σ/ρU2. As γ tends to ∞, the bubble surface tends to a circle or circular arc, and as γ decreases the bubble elongates in the direction normal to the flow. When γ reaches a certain value γ0(β), opposite sides of the bubble touch each other. The problem is formulated as an integrodifferential equation for the bubble surface. This equation is discretized and solved numerically by Newton's method. Bubble profiles, the bubble area, the surface energy and the kinetic energy are presented for various values of β and γ. In addition a perturbation solution is given for γ large when the bubble is nearly a circular arc, and a slender-body approximation is presented for β ∼ ½π and γ ∼ γ0(β), when the bubble is slender.

The anomalous wake accompanying bubbles rising in a thin gap: a mechanically forced Marangoni flow

1997 ◽  
Vol 352 ◽  
pp. 283-303 ◽  
Author(s):  
JOHN W. M. BUSH
Keyword(s):  
Surface Tension ◽  
Bubble Surface ◽  
Surface Flow ◽  
Surface Tension Gradient ◽  
Marangoni Flow ◽  
Wake Structure ◽  
Rising Bubble ◽  
Moderate Reynolds Number ◽  
Mechanical Analogue ◽  
Order Of Magnitude

A novel wake structure, observed as penny-shaped air bubbles rise at moderate Reynolds number through a thin layer of water bound between parallel glass plates inclined at a shallow angle relative to the horizontal, is reported. The structure of the wake is revealed through tracking particles suspended in the water. The wake completely encircles the rising bubble, and is characterized by a reverse surface flow or ‘edge jet’ which transports fluid in a thin boundary layer along the bubble surface from the tail to the nose at speeds which are typically an order of magnitude larger than the bubble rise speed. A consistent physical explanation for the wake structure is proposed. The wake is revealed to be a manifestation of the three-dimensionality of the flow in the suspending fluid. The bubble surface advances through a rolling motion, thus generating regions of surface divergence and convergence at, respectively, the leading and trailing edges of the bubble. A nose-to-tail gradient in surfactant concentration is thus established, and the associated surface tension gradient drives the edge jet. The dependence of the wake structure on the suspending fluid is examined experimentally.Surfactants play an anomalous role in the reported flow, serving to promote rather than suppress surface motions. The wake structure is an example of a mechanically forced Marangoni flow, and so represents a mechanical analogue of that accompanying thermocapillary drop motion in microgravity. A theoretical model is developed which reproduces the salient features of the flow, and on the basis of which an estimate is made of the mechanically induced surface tension gradient along the bubble surface.

Effect of organic matter on bubble surface tension

1996 ◽  
Vol 101 (C2) ◽  
pp. 3769-3774 ◽  
Author(s):  
David E. Slauenwhite ◽  
Bruce D. Johnson
Keyword(s):  
Surface Tension ◽  
Organic Matter ◽  
Bubble Surface

Marangoni effects caused by contaminants adsorbed on bubble surfaces

2010 ◽  
Vol 647 ◽  
pp. 143-161 ◽  
Author(s):  
PETER LAKSHMANAN ◽  
PETER EHRHARD
Keyword(s):  
Surface Tension ◽  
Shear Stress ◽  
Contaminant Transport ◽  
Level Set ◽  
Solid Sphere ◽  
Bubble Surface ◽  
Stress Profile ◽  
Air Bubbles ◽  
Shear Stress Profile ◽  
Marangoni Effects

The influence of Marangoni stresses, caused by contaminants adsorbed on the surface of small air bubbles, rising in water, is examined by numerical simulations. A modified level set method is used to represent the deformable bubble interface, extended by a model for the contaminant transport on the bubble surface. We show that surface tension variations of less than 2% are sufficient to generate Marangoni stresses that are strong enough to change the rising characteristics of a bubble to that of a corresponding solid particle. In such situations, we find that the bubble surface is fully covered with contaminant and the shear stress profile resembles the shear stress profile around a solid sphere.

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