Escott, Liam James;
(2022)
The rheology of weakly-viscoelastic multiphase systems using a cell model.
Doctoral thesis (Ph.D), UCL (University College London).
Preview |
Text
Liam_Escott_Thesis.pdf - Other Download (8MB) | Preview |
Abstract
We consider the rheology in bulk of three multiphase systems: a suspension of rigid spheres, a suspension of elastic spheres and a two-phase fluid system. In all cases, we use the second-order fluid model to capture the first effects of viscoelasticity. The deformability of the secondary phase, where applicable, is calculated locally and contributes to the bulk behaviour of the system. We attribute, to each sphere-like object comprising secondary phase, a mean-field cell model. This cell model is considered a proxy by which we reach beyond the dilute limit, where fully analytical results can be derived, to higher concentrations of the secondary phase. The whole suspension or two-phase fluid system is described in terms of a semi-analytical constitutive equation, itself a second-order fluid with modified material parameters. We find that, in simple shear of a rigid solid suspension, there is no volume fraction dependence in the ratio of first normal stress difference to shear stress. However, we do find a change of sign in the corresponding ratio for second normal stress difference upon increase in concentration. Upon introducing elastic particles instead of the previous rigid case, we use a deformation dependent empirical model to derive a slight shear-thinning behaviour in effective viscosity. Further, we find increasing and decreasing first and second normal stress difference respectively upon decrease in solid shear modulus, for fixed solid volume fraction. In both the elastic solid suspension and two-phase fluid emulsion, there is an increase in first normal stress difference with increasing deformation, normalised by shear stress where none was found in the rigid case. With respect to the second normal stress difference, we again find a change of sign from negative to positive. It would be justifiable to apply this model to all flows which can be described via the second-order fluid expansion.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | The rheology of weakly-viscoelastic multiphase systems using a cell model |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2022. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Mathematics UCL |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10151771 |
Archive Staff Only
 |
View Item |
