Show simple item record

dc.contributor.advisorThoroddsen, Sigurdur T
dc.contributor.authorTian, Yuansi
dc.date.accessioned2020-08-31T13:37:44Z
dc.date.available2020-08-31T13:37:44Z
dc.date.issued2020-06
dc.identifier.citationTian, Y. (2020). Experiments on Drop-impact Splashing, Singular Jets and Coalescence in Emulsions. KAUST Research Repository. https://doi.org/10.25781/KAUST-7N1YP
dc.identifier.doi10.25781/KAUST-7N1YP
dc.identifier.urihttp://hdl.handle.net/10754/664909
dc.description.abstractThis dissertation describes experiments on drop dynamics. It is split into two main parts: The first investigates the breakup of liquid during the impact of a drop on a pool surface, with focus on the smallest and fastest splashed satellite droplets. The second part studies the much slower coalescence of two minute water droplets in oil inside a micro-channel, with applications to separation of water droplets from crude oil emulsions. First, we study drop-on-liquid impacts in high-speed experiments with extreme time and spatial resolutions using up to 5 million frames-per-second video imaging. This is used to identify and explain two primary mechanisms which produce the smallest and fastest splashed secondary droplets, i.e. ejecta sheets and singular jets. Using a novel 25-m-tall vacuum tube we generate very large impact velocities, to reach regimes in parameter-space never studied before. During the earliest stage of the impact a fast-moving horizontal ejecta sheet emerges from the neck between drop and pool. The breakup of this sheet forms a myriad of micron-size droplets. The ejecta bending is dominated by air resistance, which we investigate under reduced ambient pressures and successfully model based on Bernoulli suction which pulls down the ejecta to hit the pool surface. The ejecta can initially bend up or down depending on the relative viscosities of the drop and pool, bending up if the pool is less viscous. Singular jets are produced by the collapse of drop-impact craters for deep pools, when a dimple forms at the bottom of the crater focusing the energy into a micron-sized region, with jetting velocities over 100 m/s. We use Gerris to study the fine details, obscured in the experiments. In the second part, we study the coalescence of water droplets inside an oil emulsion, developing an empirical relation between the coalescence interaction time tc and the modified shear-rate. This is done by tracking 3-D drop trajectories inside a microchannel, with two perpendicular high-speed cameras. For droplets in crude oil, we implement near-infrared visualization in an innovative device to quantify demulsifier efficiency, using mono-disperse micro-droplets.
dc.language.isoen
dc.subjectsplashing
dc.subjectsingular jets
dc.subjectcoalescence
dc.subjectdrop impact
dc.titleExperiments on Drop-impact Splashing, Singular Jets and Coalescence in Emulsions
dc.typeDissertation
dc.contributor.departmentPhysical Science and Engineering (PSE) Division
dc.rights.embargodate2021-08-30
thesis.degree.grantorKing Abdullah University of Science and Technology
dc.contributor.committeememberSamtaney, Ravi
dc.contributor.committeememberSun, Shuyu
dc.contributor.committeememberCastrejon-Pita, Jose Rafael
thesis.degree.disciplineMechanical Engineering
thesis.degree.nameDoctor of Philosophy
dc.rights.accessrightsAt the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation will become available to the public after the expiration of the embargo on 2021-08-30.
kaust.request.doiyes


Files in this item

Thumbnail
Name:
PhD_Dissertation_Yuansi_Tian_Final0809.pdf
Size:
51.20Mb
Format:
PDF
Description:
Dissertation - Yuansi Tian

This item appears in the following Collection(s)

Show simple item record