Thesis
OUTCOMES FOLLOWING DROPLET IMPACT ON A HYDROPHILIC SUBSTRATE: SPREADING, JETTING, AND PARTIAL REBOUND
Washington State University
Master of Science (MS), Washington State University
01/2022
DOI:
https://doi.org/10.7273/000004510
Handle:
https://hdl.handle.net/2376/125062
Abstract
Droplet impact on a solid surface, while ubiquitous, still has many facets to be explored. One of these is the influence of surface characteristics, which we have analyzed through the examination of a novel substrate that is both hydrophilic and microstructured with arrays of pillars. The ability to predict the outcomes following droplet impact such as maximum spreading, jetting, breakup, and partial rebound are crucial in the practical applications of this surface or similar instances. Impacts and the events thereafter were studied for this substrate by impinging water-glycerol solutions of varying viscosity and release height. From our work we have found that the maximum spreading factor, βmax = Dmax/Di, is largely unaffected by the consideration of viscous effects due to the micropillars. Spreading of the droplet can therefore be characterized by a simple scaling of βmax ~ We1/4 found by energy conservations methods. For jetting, we have found that surface wettability and the velocity profile across the jet greatly affect the evolution of the jet dimensions over time, with the jet tip radius and height straying from the typical scaling factor of 2/3 and maintaining average values of 1/5 and 1, respectively. Analyzing partial rebound for our substrate, we have found that this outcome exhibits a near constant volume ratio when comparing the rebounded portion to the original droplet. We find evidence this is likely due to the maximum retraction height before breakup, which is at least two times greater than the capillary length of the fluid. Partial rebound is also found to possess a threshold energy at maximum retraction of 0.5 µW, above which partial rebound is the most likely outcome. For all outcomes, we derive a scaling that infers breakup time is only dependent upon impact conditions, such as impact velocity and fluid properties, and is unrelated to the outcome of the droplet itself. Utilizing these latest outcome characteristics, we are able to further parameterize impact on hydrophilic and micropillared substrates and expand our understanding of the underlying dynamics of spreading, jetting, and partial rebound for this surface.
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Details
- Title
- OUTCOMES FOLLOWING DROPLET IMPACT ON A HYDROPHILIC SUBSTRATE
- Creators
- Brooklyn Asai
- Contributors
- Hua Tan (Advisor)Stephen A. Solovitz (Committee Member)Linda Chen (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Engineering and Computer Science (VANC), School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Number of pages
- 72
- Identifiers
- 99900877038701842
- Language
- English
- Resource Type
- Thesis