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Bubble Growth from Submerged Orifices: Investigating the Influence of Surface Wettability, Liquid Properties, and Design Conditions

Manoharan, Sanjivan
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479819854513389

Abstract Details

2016, PhD, University of Cincinnati, Engineering and Applied Science: Mechanical Engineering.
The effects of surface wettability, liquid properties, and design conditions on bubble growth from orifice plates and capillary orifices submerged in liquid pools have been experimentally and computationally studied. For orifice plates submerged in water, above a certain critical contact angle, the bubble base was observed to spread away from the orifice resulting in larger bubbles at departure. By scaling the forces acting on the bubble and using a minimum energy approach, a correlation to predict the static regime equivalent bubble departure diameter was proposed using data obtained from the current experiments and existing literature. Following this, ebullience in aqueous surfactant solutions was investigated. First, bubble growth from a capillary-tube orifice submerged in pools of aqueous surfactant (SDS and CTAB) was studied. A new numerical treatment was developed to determine the surfactant transport and adsorption/desorption in the interface region. From the variation of the surfactant interfacial concentration, the spatio-temporal variation in interfacial tension is determined. Due to the resulting variation in interfacial tension, the shapes and sizes of bubbles in surfactant solution are different from those in pure liquid. The results were compared to those obtained from experiments and were found to be in excellent agreement. Experiments were then conducted for orifice plates submerged in SDS with varying concentrations. Ethanol-water binary mixtures of similar liquid-vapor interfacial tensions were also used in order to decouple the compound effect of surface tension and contact angle on bubble size. It was found that there was a critical surface tension below which spreading of the bubble base was absent even for super-hydrophobic surfaces such as Teflon. However for such surfaces, beyond the critical surface tension, there was a sharp increase in the bubble size due to surface dewetting. This increase in bubble size was not linear but more of an `s’ shaped one. In addition to variation in orifice diameter, chamber volume, another design parameter, was also varied to study the influence on ebullience in water and binary mixtures. The chamber volume effects were first studied using Plexiglass, a hydrophilic orifice plate. Two different chamber volumes and several orifice diameters were used to vary the degree of chamber effects. In the presence of chamber effects, the bubbles were larger, more spherical with a sharp apex, sat closer to the orifice plate, and had smaller growth times. For the medium chamber region, an empirical correlation was proposed to predict bubble departure diameters to within ±15%. For Teflon (hydrophobic), introducing chamber effects resulted in a decrease in spread of the bubble base. The net effect was no change in bubble sizes for the considered diameter range due to both effects (increased chamber volume and decreased bubble spreading) opposing each other. However, bubble characteristics such as shape, growth time, and spread behavior were affected. Finally, bubble growth in more viscous liquids on hydrophobic and hydrophilic surfaces with varying orifice diameters was experimentally investigated. For larger orifice diameters, viscous effects were only present beyond a certain flow rate. For such orifices, beyond a certain flow rate, there was a reduction in bubble size on Teflon due to the bubble base spread being suppressed. However, this was evident only above a certain viscosity threshold. For small orifice diameters, viscosity effects were seen at all flow rates. Bubble characteristics during and after the growth phase have been studied.
Milind Jog, Ph.D. (Committee Chair)
Yuen Koh Kao, Ph.D. (Committee Member)
Raj Manglik, Ph.D. (Committee Member)
David Thompson, Ph.D. (Committee Member)
239 p.
Mechanical Engineering; Mechanics
Bubble dynamics; Surface Wettability; Contact Angle; Chamber volume; Surfactant; Dynamic Surface Tension

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Citations

  • Manoharan, S. (2016). Bubble Growth from Submerged Orifices: Investigating the Influence of Surface Wettability, Liquid Properties, and Design Conditions [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479819854513389

    APA Style (7th edition)

  • Manoharan, Sanjivan. Bubble Growth from Submerged Orifices: Investigating the Influence of Surface Wettability, Liquid Properties, and Design Conditions. 2016. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479819854513389.

    MLA Style (8th edition)

  • Manoharan, Sanjivan. "Bubble Growth from Submerged Orifices: Investigating the Influence of Surface Wettability, Liquid Properties, and Design Conditions." Doctoral dissertation, University of Cincinnati, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479819854513389

    Chicago Manual of Style (17th edition)

ucin1479819854513389
408
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This open access ETD is published by University of Cincinnati and OhioLINK.