Visualization of Multiscale Processes - Bubble Dynamics in Surface Active Colloids

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
S. Manoharan ◽  
D. Kalaikadal ◽  
R. M. Manglik ◽  
E. Iskrenova-Ekiert ◽  
S. S. Patnaik
Keyword(s):  
Molecular Dynamics ◽  
Surface Tension ◽  
Pure Water ◽  
Dynamic Surface Tension ◽  
Air Flow Rate ◽  
Dynamic Surface ◽  
Multi Scale ◽  
Macro Scale ◽  
Dynamics Simulations ◽  
Adsorption Desorption

The growth dynamics of isolated gas bubbles from a submerged capillary-tube orifice in a pool of aqueous solution of Cetyl Trimethyl Ammonium Bromide (CTAB) was studied by multi-scale modeling. The macro-scale bubble ebullience is controlled by the molecular scale surfactant adsorption/desorption on the liquid-gas interface. Molecular dynamics simulations were carried out to predict the interfacial adsorption/desorption kinetics. The results of the molecular dynamics simulations were input to the volume-of-fluid based macro-scale computations. The size and shape of bubbles from incipience to departure were measured using high speed videography for model validation. Predictions of the multi-scale model agree with the experimental measurements of bubble size evolution and bubble diameter at departure. The surfactant mass transfer and adsorption on the liquid gas interface gives rise to dynamic surface tension. As a result of the surfactant presence, the bubble departure diameters were smaller in CTAB solution compared to pure water. Furthermore, dynamic surface tension behavior of CTAB makes the bubble departure diameter a function of bubble Reynolds number (Re based on the orifice diameter and air flow rate). At low flow rates or low Re, the bubble departure diameters are smaller than those in water. As the air flow rate increases, the bubble departure diameters tend towards those in pure water. The authors gratefully acknowledge funding from AFOSR Thermal Science Program and AFRL DoD Supercomputing Resource Center for computing time and resources.

Additive Adsorption and Interfacial Characteristics of Nucleate Pool Boiling in Aqueous Surfactant Solutions

2005 ◽  
Vol 127 (7) ◽  
pp. 684-691 ◽  
Author(s):  
Juntao Zhang ◽  
Raj M. Manglik
Keyword(s):  
Contact Angle ◽  
Pure Water ◽  
Pool Boiling ◽  
Dynamic Surface Tension ◽  
Nucleate Pool Boiling ◽  
Dynamic Surface ◽  
Wetting Contact Angle ◽  
Optimum Heat ◽  
Adsorption Desorption ◽  
And Control

Interfacial phenomena and ebullient dynamics in saturated nucleate pool boiling of aqueous solutions of three surfactants that have different molecular weight and ionic nature are experimentally investigated. The additive molecular mobility at interfaces manifests in a dynamic surface tension behavior (surfactant adsorption–desorption at the liquid–vapor interface), and varying surface wetting (contact angle) with concentration (surfactant physisorption at the solid–liquid interface). This tends to change, enhance, and control the boiling behavior significantly, and an optimum heat transfer enhancement is obtained in solutions at or near the critical micelle concentration (CMC) of the surfactant. Furthermore, wettability (contact angle) is observed to be a function of the molecular makeup of the reagent, and shows distinct regions of change along the adsorption isotherm that are associated with the aggregation mode of adsorbed ions at the solid–water interface. This distinguishably alters the ebullience from not only that in pure water, but also between pre- and post-CMC solutions. Increased wetting tends to suppress nucleation and bubble growth, thereby weakening the boiling process.

Experimental Investigation of Low Weber Number Post-Impact Drop Spreading on Solid Substrates

2010 ◽  
Author(s):  
Milind A. Jog ◽  
Raj M. Manglik
Keyword(s):  
Surface Tension ◽  
High Speed ◽  
Pure Water ◽  
Surfactant Solution ◽  
Video Camera ◽  
Dynamic Surface Tension ◽  
Temporal Variations ◽  
Dynamic Surface ◽  
Post Impact ◽  
Triton X

The post-impact spreading and recoil behaviors of droplets of pure liquids (water and ethanol) and aqueous solution of Triton X-100 (a surfactant) on a dry horizontal hydrophilic (glass) substrate are investigated for low Weber numbers. The evolution of drop shape during spreading and recoil are captured using a high-speed (4,000 frames per second) digital video camera. Digital image-processing was used to determine the spread and height of the liquid film on the surface from each frame. Unlike pure liquids, the liquid-gas interfacial tension for surfactant solution is a function of surface age, where surface tension is that of the solvent at zero time and then reaches an equilibrium value with increasing surface age. Furthermore, the equilibrium surface tension is a function of the surfactant concentration, which decreases from that of the solvent at zero concentration to that at the critical micelle concentration (CMC), and remains essentially constant thereafter. The surface tension of aqueous Triton X-100 solution varies from that of pure water to nearly that of ethanol. As such the comparison of transient droplet-impact-spreading-recoil behavior of the three liquids, or their temporal variations of the spread and the flattening factor, provides a basis for understanding the role of dynamic surface tension and surface wettability.

scholarly journals Glycine in aerosol water droplets: a critical assessment of Köhler theory by predicting surface tension from molecular dynamics simulations

2011 ◽  
Vol 11 (2) ◽  
pp. 519-527 ◽  
Author(s):  
X. Li ◽  
T. Hede ◽  
Y. Tu ◽  
C. Leck ◽  
H. Ågren
Keyword(s):  
Molecular Dynamics ◽  
Surface Tension ◽  
Molecular Dynamics Simulations ◽  
Global Climate ◽  
Pure Water ◽  
Model Systems ◽  
Water Droplets ◽  
Cloud Droplets ◽  
Kohler Theory ◽  
Dynamics Simulations

Abstract. Aerosol particles in the atmosphere are important participants in the formation of cloud droplets and have significant impact on cloud albedo and global climate. According to the Köhler theory which describes the nucleation and the equilibrium growth of cloud droplets, the surface tension of an aerosol droplet is one of the most important factors that determine the critical supersaturation of droplet activation. In this paper, with specific interest to remote marine aerosol, we predict the surface tension of aerosol droplets by performing molecular dynamics simulations on two model systems, the pure water droplets and glycine in water droplets. The curvature dependence of the surface tension is interpolated by a quadratic polynomial over the nano-sized droplets and the limiting case of a planar interface, so that the so-called Aitken mode particles which are critical for droplet formation could be covered and the Köhler equation could be improved by incorporating surface tension corrections.

Adsorption of C14EO8 at the interface between its aqueous solution drop and air saturated by different alkanes vapor

2017 ◽  
Vol 19 (3) ◽  
pp. 2193-2200 ◽  
Author(s):  
R. Miller ◽  
E. V. Aksenenko ◽  
V. I. Kovalchuk ◽  
V. B. Fainerman
Keyword(s):  
Aqueous Solution ◽  
Surface Tension ◽  
Pure Water ◽  
Dynamic Surface Tension ◽  
Dynamic Surface ◽  
Equilibrium Surface ◽  
Equilibrium Surface Tension

The dynamic and equilibrium surface tension for drops of aqueous C14EO8 solutions at the interface to pure air or pentane, hexane, heptane and toluene saturated air, and the dynamic surface tension of pure water at these interfaces are presented.

scholarly journals Glycine in aerosol water droplets: a critical assessment of Köhler theory by predicting surface tension from molecular dynamics simulations

2010 ◽  
Vol 10 (10) ◽  
pp. 23169-23196 ◽  
Author(s):  
X. Li ◽  
T. Hede ◽  
Y. Tu ◽  
C. Leck ◽  
H. Ågren
Keyword(s):  
Molecular Dynamics ◽  
Surface Tension ◽  
Molecular Dynamics Simulations ◽  
Global Climate ◽  
Pure Water ◽  
Model Systems ◽  
Water Droplets ◽  
Cloud Droplets ◽  
Kohler Theory ◽  
Dynamics Simulations

Abstract. Aerosol particles in the atmosphere are important participants in the formation of cloud droplets and have significant impact on cloud albedo and global climate. According to the Köhler theory which describes the nucleation and the equilibrium growth of cloud droplets, the surface tension of an aerosol droplet is one of the most important factors that determine the critical supersaturation of droplet activation. In this paper, with specific interest to remote marine aerosol, we predict the surface tension of aerosol droplets by performing molecular dynamics simulations on two model systems; the pure water droplets and glycine in water droplets. The curvature dependence of the surface tension is interpolated by a quadratic polynomial over the nano-sized droplets and the limiting case of a planar interface, so that the so-called Aitken mode particles which are critical for droplet formation could be covered and the Köhler equation could be improved by incorporating surface tension corrections.

scholarly journals Drop Size Dependence of the Apparent Surface Tension of Aqueous Solutions in Hexane Vapor as Studied by Drop Profile Analysis Tensiometry

2020 ◽  
Vol 4 (3) ◽  
pp. 29
Author(s):  
Valentin B. Fainerman ◽  
Volodymyr I. Kovalchuk ◽  
Eugene V. Aksenenko ◽  
Altynay A. Sharipova ◽  
Libero Liggieri ◽  
...  
Keyword(s):  
Surface Tension ◽  
Drop Size ◽  
Profile Analysis ◽  
Pure Water ◽  
Dynamic Surface Tension ◽  
Dynamic Surface ◽  
Hexane Vapor ◽  
Wide Range ◽  
Drop Profile Analysis Tensiometry ◽  
Hexane Phase

Surface tension experiments were performed using the drop profile analysis tensiometry method. The hexane was injected into the measuring cell at certain times before the formation of the solution drop. The influence of the capillary diameter and solution drop size on the measured apparent dynamic surface tension was studied. The amount of hexane transferred from the vapor phase to the drop was estimated. For large pure water drops, it was shown that the ageing of the drop in the hexane vapor during a long time resulted in the formation of a liquid hexane phase covering the drop, but the volume of this phase did not exceed 0.5 mm3. On the contrary, for surfactant solution drops the volume of the hexane phase covering the drop was essentially larger. Experiments with solution drops were performed to measure the surface tension within a wide range of surfactant concentration. It was found that the dependencies of dynamic surface tension on the C13DMPO and C14EO8 solutions concentration exhibit maxima at concentrations of about 1–2 μmol/L for C14EO8 and 2–5 μmol/L for C13DMPO at ageing times of 100 to 1000 s; these maxima were shown to exist also at equilibrium. This phenomenon is presumably ascribed to the competitive character of simultaneous adsorption of hexane and surfactant.

scholarly journals Dynamic Surface Tension Enhances the Stability of Nanobubbles in Xylem Sap

2021 ◽  
Vol 12 ◽  
Author(s):  
Stephen Ingram ◽  
Yann Salmon ◽  
Anna Lintunen ◽  
Teemu Hölttä ◽  
Timo Vesala ◽  
...  
Keyword(s):  
Surface Tension ◽  
Surface Composition ◽  
Xylem Sap ◽  
Dynamic Surface Tension ◽  
External Pressure ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Dynamic Surface ◽  
Biologically Relevant ◽  
Dynamics Simulations

Air seeded nanobubbles have recently been observed within tree sap under negative pressure. They are stabilized by an as yet unidentified process, although some embolize their vessels in extreme circumstances. Current literature suggests that a varying surface tension helps bubbles survive, but few direct measurements of this quantity have been made. Here, we present calculations of dynamic surface tension for two biologically relevant lipids using molecular dynamics simulations. We find that glycolipid monolayers resist expansion proportionally to the rate of expansion. Their surface tension increases with the tension applied, in a similar way to the viscosity of a non-Newtonian fluid. In contrast, a prototypical phospholipid was equally resistant to all applied tensions, suggesting that the fate of a given nanobubble is dependent on its surface composition. By incorporating our results into a Classical Nucleation Theory (CNT) framework, we predict nanobubble stability with respect to embolism. We find that the metastable radius of glycolipid coated nanobubbles is approximately 35 nm, and that embolism is in this case unlikely when the external pressure is less negative than –1.5 MPa.

Dynamic surface tension of xylem sap at the air-water interface

2021 ◽  
Author(s):  
Reddy Prasanna Duggireddy ◽  
Eran Raveh ◽  
Gilboa Arye
Keyword(s):  
Surface Tension ◽  
Surface Activity ◽  
Pure Water ◽  
Xylem Sap ◽  
Dynamic Surface Tension ◽  
Bulk Solution ◽  
Diffusion Control ◽  
Dynamic Surface ◽  
Equilibrium Surface Tension ◽  
Air Interface

<p>The surface tension (ST) of xylem sap at the water-air interface is a crucial phenomenon, influencing many physiological events such as air seeding and embolism, by which xylem vessels become air-filled and cease to function. Refilling of embolized, may relies on sap’s surface activity at the interface. It is commonly assumed that the ST of xylem sap is equal to the ST of pure water (72 mN/m). However, xylem sap is a complex solution and consists of surface-active molecules that may adsorb and accumulate at the water-air interface and thereby reduce the ST of water as a function of their aqueous concentration. However, when a new water-air interface is formed, equilibrium ST is not reached instantaneously. Specifically, amphiphilic molecules are kinetically adsorbed and undergo orientation at the interface following diffusion from the bulk solution. Dynamic ST of xylem sap and liquid-solid interactions, describing the surface phenomena of the xylem of vascular plants is currently not fully understood. This is mainly due to a lack of quantitative knowledge on the rate and extent of dynamic and equilibrium ST of sap. In this regard, the main objective of this study is to quantify the dynamic and equilibrium ST of xylem sap as a function of their aqueous concentration. We extracted xylem sap from lemon trees and measured ST as a function of time using the pendant drop technique. The dynamic ST data were analyzed using empirical and diffusion-control mathematical models which adequately described the exponential-like decay of the ST as a function of time. The results showed reduced ST of water in the xylem sap, indicating significant surface activity, reaching equilibrium ST values as low as 42 mN/m. The rate of ST decay was higher in high sap concentration and reduced in diluted one. The results of dynamic and equilibrium ST and the corresponding model will be presented and their implications for xylem hydraulic functioning will be discussed.</p><p> </p><p>Keywords: Dynamic surface tension, Equilibrium surface tension, Diffusion, Xylem sap.</p><p> </p>

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