Loading...

Numerical Simulation of Forced Impregnation in a Thick Capillary Tube

Safavi, Mohammad | 2013

685 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 44446 (08)
  4. University: Sharif University of Technology
  5. Department: Mechaical Engineering
  6. Advisor(s): Mousavi, Ali
  7. Abstract:
  8. Drop penetration into the capillary tube, as a classical problem, has been studied over 100 years. But there are a few studies that investigate forced impregnation of capillary tubes, which has major application in coating, inkjet printing and rain drop penetration into the soil, have been made. A comprehensive numerical investigation on millimeter droplet impact dynamics on a thick capillary tube with micrometer sized pore is conducted and validated against experimental data. This work is extended to oblique impact of drops into pores and normal impact on nanoscaled pores. We apply the finite volume numerical method to solve the time-dependent governing equations of continuity, momentum in conjunction with the Volume of Fluid (VOF) approach for interface tracking. Surface tension, wall adhesion effect and gravitational body force dynamics are accounted for the governing equations. We observe different regimes in a normal impact of microsized drop: at low impact velocity, we recover the classical results for impregnation. The liquid does not impregnate the hydrophobic pore while it is totally sucked into the hydrophilic one. At high impact velocities, the drop is broken in two parts: one part spreads at the top of the surface while an isolated slug is trapped within the pore. We determine the critical speeds for these regimes and obtain a full phase-diagram for our observations. We observe a higher mean penetration velocity than a impact velocity at first moments of impact due the pressure rise resulting from impact. Based on energy balance analysis, an analytical solution with linear assumption is obtained. The model used in the present study includes an approach of describing the penetration mean velocity at first moments of drop impact. The penetration velocity predicted by the analytical solution is found in a good agreement with the numerical simulation results.For a hydrophilic and hydrophobic nano scaled pores; respectively, limited impregnation regime and No Impregnation regimes can be predicted in usual impact velocities. In an oblique impact, the result is similar to normal one. but the drop can only penetrates a hydrophilic pore completely, when the impact angle is approximatly normal to pore. And we can see multiple isolated slugs in hydrophobic pores with a high horizantioal impact velocity.
  9. Keywords:
  10. Capillary Tube ; Penetration ; Droplet Impact ; Oblique Impact ; Volume of Fluid ; Numerical Simulation ; Wettability

 Digital Object List

 Bookmark

No TOC