On the evaporation of sessile droplets

  • Jutta Stauber

Student thesis: Doctoral Thesis

Abstract

In this thesis the evolution of sessile droplets in different modes of evaporation and their lifetimes are investigated. The thesis focuses on situations in which the diffusion of vapour into the surrounding atmosphere is the rate-limiting mechanism of evaporation. First, we describe the evolution of droplets evaporating in the two extreme modes, namely the constant contact radius mode, in which the contact line of the droplet is always pinned, and the constant contact angle mode, in which the contact line of the droplet is always de-pinned. In particular, we demonstrate how these two modes converge on strongly hydrophobic substrates. Next we study the evolution of droplets evaporating in the stick-slide mode, in which the contact line is initially pinned and the contact angle decreases to the receding contact angle, but thereafter the contact line is de-pinned and the contact radius decreases to zero. The lifetimes of droplets evaporating in the stick-slide mode are investigated in two situations, namely when the initial and receding contact angles are independent and when there is a simple relationship between them based on the assumption of a constant maximum pinning force. In particular, it is shown that the lifetimes of droplets evaporating in this mode may be longer than those of initially identical droplets evaporating in the two extreme modes. Finally, we develop a model for the evolution of droplets evaporating in a stick-jump mode, in which the contact line pins, de-pins and re-pins multiple times. It is shown that the lifetimes of droplets evaporating in this mode may be longer or shorter than those of initially identical droplets evaporating in the two extreme modes. Good agreement is found between the predicted lifetimes of droplets in both the stick-slide and the stick-jump modes and the lifetimes of droplets determined from relevant experiments in the literature.
Date of Award1 Apr 2015
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsEPSRC (Engineering and Physical Sciences Research Council)
SupervisorStephen Wilson (Supervisor) & Brian Duffy (Supervisor)

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