Multiphase lubrication fluid flows

Lead Research Organisation: University of Manchester
Department Name: Physics and Astronomy

Abstract

This research project aims to investigate multiple phase viscous fluid systems; we aim to look specifically at the fluid flows present in the systems and the interactions between phases. To this end, the project will consist of two parts. In the first part, we will investigate the motion of microdroplets (with radii on the order of tens of microns) deposited onto silicone oil substrates with a spatial depth gradient. We hope to develop a robust theoretical model which predicts the motion of the droplets. We also aim to quantify the effect, if any, of the surface tension at the triple line of the system; to the best of our knowledge, this effect has not been investigated in the existing literature.
The second part of the project will be to investigate the reopening of collapsed, fluid-filled elastorigid channels. The base and sides of these channels are machined out of a Perspex block and the top consists of an elastic latex sheet. These channels are filled with silicone oil and then uniformly collapsed. When gas is injected into these channels, the resulting bubbles are seen to propagate with a variety of different shapes depending on the flow rate and degree of initial channel collapse. A good degree of understanding of the stability and mechanics of these systems has already been acquired through previous work; however, as the inspiration for these bench-top systems comes from studying collapsed airways in the lungs, we would like to take the existing theory and go on to investigate systems of bifurcated channels

Publications

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publication icon
Cuttle C (2020) Dynamics of front propagation in a compliant channel in Journal of Fluid Mechanics

Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509565/1 01/10/2016 30/09/2021
1830567 Studentship EP/N509565/1 19/09/2016 31/03/2020 Callum Cuttle
 
Description So far, I have performed a set of experiments with a system demonstrating aspects of fluid-structure interaction and interfacial dynamics between multiple fluid phases. To be exact, the system under investigation was the displacement of oil by the injection of air within a rigid rectangular channel, bounded by an elastic membrane on top. These problems are broadly related to the reopening of collapsed pulmonary airways in the lungs. Furthermore, the dynamics of the specific system investigated are comparable to those associated with the transition to turbulence in pipe flows, one of the key unsolved problems in physics. Due to the comparative simplicity of our system, which is largely described by linear equations, we have been able to study these complex dynamics in great detail using careful experimental measurements.

Since this work, I have moved onto the second part of my project. Again, I have been studying interfacial flows in the limit of high viscosity (low Reynolds number). This time, I've been looking at the evolution of water droplets placed onto deep layers of immiscible silicone oil. While there has been a lot of work conducted previously on the inverse problem (oil on water), this is one of the first studies looking at this particular problem. Since the oil used is perfectly wetting on the droplet, the oil will spread to cover the droplet's surface. In addition, the droplet is more dense than the oil and so must eventually sink. We have found that the exact process which leads up to the droplet finally becoming engulfed by the oil and sinking is surprisingly complex. To fully account for the dynamical picture of droplet engulfment requires a detailed analysis of effects spanning broad length- and timescales (nm to mm, and micro-seconds to hours, respectively). Our results have shown that gravitational effects, typically ignored at sufficiently small length scales where surface tension dominates, are crucial in this system down to micron-sized drops.
Exploitation Route Within the wider scientific community, our findings provide an example of a simple, quasi-2 dimensional system in which current research topics in nonlinear dynamics may be studied numerically (as well as experimentally) with relative ease. For example, we have identified so-called edge states in our system, which are unstable equilibrium states which act to guide a bistable system towards one particular stable state. These edge states have generated a lot of interest in their role in turbulent transitions as well as the break up of liquid droplets in certain flows.

Within my own department, moreover, a colleague of mine is currently working to simulate the same system and my results will serve as a means of direct comparison.

The second part of the project, looking at the engulfment of droplets, is a conceptually simple problem, and so we expect our results to find applications in a variety of settings, e.g. cleaning and decontaminaion of crude oil spills. In terms of academic interest, the problem is broadly reated to spreading dynamics, an active and expansive field of research. Typically, in spreading flows the effects of gravity diminish with time (or the extent of spreading). In our system, the opposite is true, and so our results extend the classical picture of spreading. Again, since the deposition of droplets on liquid layers is a fairly ubiquitous problem, we would expect our work to generate interest and further studies from other researchers engaded in the field.
Sectors Aerospace, Defence and Marine,Construction,Education,Energy,Healthcare,Pharmaceuticals and Medical Biotechnology

 
Description School Visit 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact CC delivered a 40 minute talk of fluid dynamics at a school in Manchester to a sixth form group interested in engineering. The group had some prior knowledge of fluid mechanics, but had not been introduced to many applications in biology and geology, which sparked interest in the students.
Year(s) Of Engagement Activity 2017