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.

Experimental Investigation of Droplet Dynamics on Solid Surfaces: Spreading and Recoil Effects

2006 ◽  
Author(s):  
Kalpak P. Gatne ◽  
Milind A. Jog ◽  
Raj M. Manglik
Keyword(s):  
Surface Tension ◽  
High Speed ◽  
Lower Surface ◽  
Video Camera ◽  
Temporal Variations ◽  
Liquid Viscosity ◽  
Viscous Effects ◽  
Droplet Dynamics ◽  
Digital Video Camera ◽  
The Impact

A study of the normal impact of liquid droplets on a dry horizontal substrate is presented in this paper. The impact dynamics, spreading and recoil behavior are captured using a high-speed digital video camera at 2000 frames per second. A digital image processing software was used to determine the drop spread and height of the liquid on the surface from each frame. To ascertain the effects of liquid viscosity and surface tension, experiments were conducted with four liquids (water, ethanol, propylene glycol and glycerin) that have vastly different fluid properties. Three different Weber numbers (20, 40, and 80) were considered by altering the height from which the drop is released. The high-speed photographs of impact, spreading and recoil are shown and the temporal variations of dimensionless drop spread and height are provided in the paper. The results show that changes in liquid viscosity and surface tension significantly affect the spreading and recoil behavior. For a fixed Weber number, lower surface tension promotes greater spreading and higher viscosity dampens spreading and recoil. Using a simple scale analysis of energy balance, it was found that the maximum spread factor varies as Re1/5 when liquid viscosity is high and viscous effects govern the spreading behavior.

Effect of Ethoxylation and Molecular Weight of Cationic Surfactants on Nucleate Boiling in Aqueous Solutions

2004 ◽  
Vol 126 (1) ◽  
pp. 34-42 ◽  
Author(s):  
Juntao Zhang ◽  
Raj M. Manglik
Keyword(s):  
Molecular Weight ◽  
Surface Tension ◽  
Aqueous Solutions ◽  
Cationic Surfactants ◽  
Bubble Dynamics ◽  
Surfactant Solution ◽  
Dynamic Surface Tension ◽  
Nucleate Boiling ◽  
Dynamic Surface ◽  
Reduce Surface Tension

Saturated, nucleate pool boiling on a horizontal, cylindrical heater and the associated bubble dynamics in aqueous solutions of cationic surfactants of different molecular weight and ethoxylation or ethylene oxide (EO) content, are experimentally investigated. Boiling curves qw″∝ΔTsat for different concentrations and photographic records of the salient features of the ebullient behavior are presented, along with a characterization of interfacial properties (surface tension and contact angle). The surfactant additive significantly alters the nucleate boiling in water and enhances the heat transfer. The enhancement increases with concentration, with an optimum obtained in solutions at or near the critical micelle concentration (c.m.c.) of the surfactant. The photographic and visual observations indicate a markedly different boiling behavior than that of water, as well as between pre- and post-c.m.c. solutions. A lower molecular weight surfactant tends to reduce surface tension faster, and show better enhancement performance than its higher molecular weight counterpart. With EO groups in its molecular chain the surfactant solution becomes more hydrophilic, and the higher wettability tends to suppress nucleation, thereby weakening the boiling process. Also, enhancement in pre-micellar solutions is shown to depend on the dynamic surface tension, and the number of EO groups in and molecular weight of the surfactant.

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.

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.

Molecular-Scale Reagent Transport-Induced Modification of Low Weber Number Droplet Impact Dynamics

2007 ◽  
Author(s):  
Kalpak P. Gatne ◽  
Raj M. Manglik ◽  
Milind A. Jog
Keyword(s):  
High Speed ◽  
Surfactant Concentration ◽  
Water Drop ◽  
Pure Water ◽  
Sodium Dodecyl ◽  
Hydrophobic Surface ◽  
Video Camera ◽  
Impact Dynamics ◽  
Dynamic Surface ◽  
The Impact

Effect of surfactant molecular mass transport on the normal impact and spreading of a droplet of its aqueous solution on dry horizontal substrates is investigated for a range of Weber numbers (We = 20 – 100). The impact dynamics, spreading and recoil behavior are captured using a high-speed digital video camera at 4000 frames per second. Digital image-processing software was used to determine the drop spread and height of the liquid film on the surface from each frame. Experiments were performed with water and with two different aqueous solutions of Sodium Dodecyl Sulphate (SDS), one at its half critical micelle concentration (CMC) and another at twice CMC, on a hydrophilic surface (glass) and a hydrophobic surface (Teflon). It is seen that surfactant concentration, its dynamic surface tension behavior, and surface wettability govern the transient impact-spreading-recoil phenomena. A droplet of SDS solution exhibits higher maximum spread and weaker surface oscillations compared to a pure water drop colliding with the same velocity. On a hydrophobic (Teflon) surface, the drop rebound is inhibited by the presence of the surfactant. These effects are more pronounced at surfactant concentration of twice CMC compared to that at half CMC.

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.

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