Thesis
On the evolution of and the deposition from an evaporating sessile droplet
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2022
- Thesis identifier
- T16330
- Person Identifier (Local)
- 201762293
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- This thesis concerns the theoretical modelling and analysis of the evolution of, and the deposition from, an evaporating sessile droplet. In particular, the thesis focuses on the diffusion-limited situation in which the diffusive transport of vapour away from the droplet in the atmosphere is the rate-limiting mechanism for evaporation. First, the evolution of a thin droplet in a shallow well of rather general shape is described both before and after the free surface of the droplet touches down on the well. In particular, it is shown that, depending on the shape of the well, touchdown can occur at the lip of the well, everywhere within the well simultaneously, or at the centre of the well. The mathematical model is validated by finding good agreement between the theoretical predictions and the results of physical experiments performed by collaborators at Durham University for the special case of a cylindrical well. Second, the effect of gravity on the shape, evolution, and lifetime of thin sessile and pendant droplets is studied for four different modes of evaporation. Droplets of arbitrary volume are investigated and the limiting behaviours for small and large droplet volumes are determined. In particular, the mathematical model confirms that the contact radius of, and the total evaporative flux from, a sessile droplet is always larger than that for a pendant droplet of the same volume. It is also shown that the lifetime of a pendant droplet is always greater than that of a sessile droplet of the same initial volume for all four modes of evaporation studied. Finally, the effect of spatial variation in the local evaporative flux on the deposition of particles from an evaporating sessile droplet is considered. A one-parameter family of spatially-varying local evaporative fluxes that captures a wide range of qualitatively different behaviours is investigated. It is shown that the flow within, and the deposition from, an evaporating droplet depends strongly on the local evaporative flux profile. In particular, the mathematical model predicts three qualitatively different deposit types depending on the spatial variation in the local evaporative flux, namely, a ring deposit, a paraboloidal deposit, and a deposit at the centre of the droplet.
- Advisor / supervisor
- Wilson, Stephen
- Resource Type
- DOI
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PDF of thesis T16330 | 2022-11-03 | Public | Download |