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Investigation of Drop Generation from Low Velocity Liquid Jets and its Impact Dynamics on Thin Liquid Films

Rajendran, Sucharitha
http://orcid.org/0000-0002-0854-0648
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1512038966865923

Abstract Details

2017, PhD, University of Cincinnati, Engineering and Applied Science: Mechanical Engineering.
Drop generation from jet breakup and drop-impact on thin films are two key processes in many spray, coating and deposition applications which are experimentally and computationally investigated in this dissertation. A high-speed camera is used to capture the drop formation and its impingement on thin films and a modified volume of fluid (VOF) method is used to accurately simulate jet/film breakup. It is shown that the proposed modifications in interfacial property evaluations for VOF method provide accurate predictions of moving interface for highly viscous liquids. To understand the parameters governing uniform drop generation, a numerical study of the jet disintegration process, supplemented by experimental observations, is conducted. The simulations show that while an increase in viscous force offers greater resistance to propagation of the surface undulations thus resulting in stretching of the liquid jet, surface tension determines the radius of curvature of the pinch-off location. The interplay of these two forces leads to deviations from uniform drop generation and two different modes of liquid jet pinch-off that lead to satellite drop creation are observed. It is shown that the occurrence of these modes is governed by the liquid Morton number. A semi-empirical relation is proposed to predict the onset of the two modes. In most spray applications, the drops formed from a jet are incident on a target surface usually with a thin layer of liquid film. While viscous resistance to impact of the drop is offered by the film thus controlling drop spreading and crown formation, surface tension is noted to primarily govern the growth and eventual break-up of the ejected crown. An empirical relation for the onset of splash is obtained from high-speed image analyses of the drop-film interactions. Numerical simulation of the process indicates that the contribution of the target film and impacting drop in the creation of ejected crown depends on the film thickness. At low liquid film thickness, the liquid from the impacting drop primarily forms a jet that is ejected post-impact. For thicker films, the liquid layer absorbs a part of the energy from the impacting drop and thus the ejected jet is formed from both the impacting drop as well as the liquid layer. The temporal dynamics of deposition of Newtonian drops on thin films indicates that while surface tension and inertial forces govern resultant crown height, their contribution on crown diameter is not as significant. Viscosity is noted as the key factor that governs the crown diameter. In addition, experimental investigation of drop impact dynamics of shear thinning polymeric solution is carried out to understand the effects of solution rheology on the temporal dynamics. For aqueous solution of HEC 250 HHR, the apparent viscosity is low during initial impact (high shear rate) and this increases the likelihood of splashing compared to a Newtonian liquid with the same zero shear viscosity. High-speed images of drop impact on thin film of aqueous solution of PEO WSR 303 indicate that extensional viscosity also plays an important role in governing the post-impact behavior.
Milind Jog, Ph.D. (Committee Chair)
Woo Kyun Kim, Ph.D. (Committee Member)
Raj Manglik, Ph.D. (Committee Member)
Kumar Vemaganti, Ph.D. (Committee Member)
214 p.
Engineering
drop impact; jet breakup; viscous liquid; Volume of fluid; OpenFOAM; drop generation

Recommended Citations

Citations

  • Rajendran, S. (2017). Investigation of Drop Generation from Low Velocity Liquid Jets and its Impact Dynamics on Thin Liquid Films [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1512038966865923

    APA Style (7th edition)

  • Rajendran, Sucharitha. Investigation of Drop Generation from Low Velocity Liquid Jets and its Impact Dynamics on Thin Liquid Films. 2017. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1512038966865923.

    MLA Style (8th edition)

  • Rajendran, Sucharitha. "Investigation of Drop Generation from Low Velocity Liquid Jets and its Impact Dynamics on Thin Liquid Films." Doctoral dissertation, University of Cincinnati, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1512038966865923

    Chicago Manual of Style (17th edition)

ucin1512038966865923
262
© 2017, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.