The effect of viscoelastic fluids on flows generated by spherical objects during sedimentation

Abstract

This thesis describes and analyses sedimentation experiments of a bead in various concentrations of aqueous PEG. These experiments are intended to be first order approximations of free-swimming organisms sedimenting in viscoelastic fluids and serve as a precursor to further experiments involving free-swimming organisms swimming in viscoelastic fluids. The post-processed data from these experiments are presented as colour maps in graphs of Reynolds number versus Deborah number, revealing that the velocity and vorticities are more sensitive to changes in Reynolds number than in Deborah number. However, for the range of viscoelastic fluids experimented with, no quantitative trends were apparent. As such, further experiments will need to be conducted to gain information about the velocity and viscosity maps from a wider range of viscoelastic fluids. Further improvements to the current setup are also suggested and outlined where possible.