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Effects of Interfacial and Viscous Properties of Pure Liquids and Polymeric Solutions on Drop Spread Dynamics

Ravi, Vishaul
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1331300235

Abstract Details

2012, MS, University of Cincinnati, Engineering and Applied Science: Mechanical Engineering.
An experimental study of the post-impact spreading of liquid droplets on dry horizontal substrates is presented in this paper. The drop spreading and recoil behaviors are captured using a high-speed digital video camera at 2000 frames per second. To ascertain the effects of liquid interfacial and viscous properties, experiments were conducted with five liquids (water, ethylene glycol, propylene glycol, glycerin, and acetic anhydride). A range of drop Weber number from 20 to 120 was considered by altering the height from which the drop is released. Effects of liquid properties on droplet spread-recoil dynamics were determined by comparing the results of liquids with different surface tension but similar viscosity and vice versa. 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. 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 recoil. Also, spread, recoil and shape oscillations were more pronounced on a hydrophobic substrate (Teflon) compared to those on a hydrophilic substrate (glass). A detailed comparison of maximum spreads observed in the experiments with those obtained using spread correlations available in the literature show significant differences. Limitations of the available correlations are discussed in the paper. The post-impact spreading and recoil behaviors of liquid droplets of pure water, water glycerol solution, ethylene glycol and two different grades of non-Newtonian aqueous solution of Hydroxy ethyl cellulose (HEC), namely HR and MR on dry horizontal hydrophobic (Teflon) and hydrophilic (glass) substrates. To understand the iii effects of non-Newtonian viscous character of aqueous polymeric solutions on postimpact spreading, the behavior of a particular concentration of HEC-MR solution with identical surface tension and zero-shear rate viscosity is compared with water glycerol solution. A range of drop Weber number from 0 (sessile drop) to 200 was 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, height, and the dynamic variation of the contact angle are provided in the paper. The shear rate dependent viscosity of aqueous polymeric solutions aids drop spreading compared to water-glycerol drops but dampens drop recoil and is results claiming the effects have been shown. At low Weber numbers (low shear rate during spreading), the maximum spread of the HEC solution droplets are comparable to those of water-glycerol solution droplets whereas at high Weber numbers (high shear rate during spreading), the maximum spread of HEC solution droplets are closer to those of water droplets. The same effect was seen when ethylene glycol and an aqueous solution of HEC-HR were compared. Experiments were also conducted at Weber numbers, 20, 100 and 200 with droplets of smaller diameter to witness the effects of increase shear rates on the aqueous polymeric solutions and compared with the droplet impact effect of the bigger droplets. The results obtained point to the fact that the droplet spread and recoil is a function of the Reynolds number. The reduction in the different energies possessed by the droplets have been discussed to explain the drop in the maximum spread factor with the diameter of the droplet.
Milind Jog, PhD (Committee Chair)
Jude Iroh, PhD (Committee Member)
Raj Manglik, PhD (Committee Member)
111 p.
Chemistry
Surface Tension; liquid droplet impact; Horizontal surfaces; recoil; experimental; non-newtonian;

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Citations

  • Ravi, V. (2012). Effects of Interfacial and Viscous Properties of Pure Liquids and Polymeric Solutions on Drop Spread Dynamics [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1331300235

    APA Style (7th edition)

  • Ravi, Vishaul. Effects of Interfacial and Viscous Properties of Pure Liquids and Polymeric Solutions on Drop Spread Dynamics. 2012. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1331300235.

    MLA Style (8th edition)

  • Ravi, Vishaul. "Effects of Interfacial and Viscous Properties of Pure Liquids and Polymeric Solutions on Drop Spread Dynamics." Master's thesis, University of Cincinnati, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1331300235

    Chicago Manual of Style (17th edition)

ucin1331300235
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This open access ETD is published by University of Cincinnati and OhioLINK.