Thesis

Particles in oscillatory flows : jamming of concentrated particulate suspensions and the response of swimming algae

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Awarding institution
  • University of Strathclyde
Date of award
  • 2014
Thesis identifier
  • T13877
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Department, School or Faculty
Abstract
  • This document describes an experimental investigation of two different particle systems under conditions of oscillatory flow. The 1st system being concentrated suspensions of non-motile particles and the 2nd system being dilute suspensions of swimming algae. This document focuses on the study of the jamming of concentrated suspensions of particles (primarily in oscillatory flows), and the response of swimming algae to oscillatory shear flows. The flow characteristics of concentrated colloidal and granular suspensions are known to display a variety of interesting flow characteristics such as shear thinning and discontinuous shear thickening. These depend on a wide range of parameters such as concentration, particle size, rate of deformation and many more. During the flow of concentrated suspensions, they can change from behaving like a fluid and flowing to behaving like a solid which can fracture or yield. Many aspects of this transition are still not understood. This phenomenon has important applications in process flow of slurries, the development of light weight bullet proof vests and as a dampening fluid within vehicle suspensions. This thesis shows that when concentrated colloidal and granular suspensions are subjected to oscillatory squeeze film flow, they display reversible local flow field distortions and macroscopic shape changes which are likely related to jamming. It highlights a range of unreported behaviours of suspensions in oscillatory squeeze film flows. This document also provides rheological data on the discontinuous shear thickening and jamming of a wide variety of different suspensions in both continuous and oscillatory shear flows. Swimming micro-organisms are currently used in a wide variety of health and cosmetic products. They are also being researched for use in the production of biodiesel. Swimming algae are grown within photo-bioreactors where their swimming characteristics can have a major impact on the reactors overall efficiency. Additionally a major issue in the production of swimming algae is the need for them to be concentrated using centrifugation which is energy intensive. This thesis shows that in oscillatory shear flows, gravitactic swimming algae can order their swimming directions in the vorticity directions of the oscillating flow field. This has potential applications in the development of a method to encourage micro-swimmers to self-concentrate. Suggestions of other investigations into the ordering behaviour of swimming micro-organisms are also provided. This document also displays a unique and cheap method for applying oscillatory squeeze film flows while allowing samples to be viewed underneath a microscope. It also makes suggestions on how this method could be enhanced. This device has applications in carrying out squeeze film tests to examine the rheological properties of fluids.
Resource Type
DOI
Date Created
  • 2014
Former identifier
  • 1041623

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