## Citation

Song, Yichuan
(2022)
*Rheological Measurements in Moderate Reynolds Number Liquid-Solid Flows.*
Dissertation (Ph.D.), California Institute of Technology.
doi:10.7907/5ey8-v324.
https://resolver.caltech.edu/CaltechTHESIS:06062022-033735914

## Abstract

Liquid-solid flows with inertial and viscous effects are critical for many engineering and geophysical applications, such as the processing of biomass slurry and the control of debris flows. However, modeling the rheological behaviors of these complex flows remains a challenge. Prior investigations on the liquid-solid flows typically cover suspensions in which the particle Reynolds numbers (*Re*) based on the particle diameter and shear rate are less than 1. Limited prior study at Caltech focuses on particle Reynolds numbers above 10. This thesis focuses on rheological experiments for the moderate Reynolds number regime where both inertial and viscous effects are important, with particle Reynolds numbers from 0.5 to 800. The rheological experiments include torque measurements of *mm* scale-sized polystyrene and SAN particles with a range of solid fractions from 10% to 50%, considering both neutrally-buoyant and settling suspensions with density ratios of 1 and 1.05. This thesis discusses rheological measurements of three different fields: pure fluids, neutrally-buoyant suspensions, and non-neutrally-buoyant suspensions.

The pure fluids measurements determine the flow starts to transition to turbulent flow for gap Reynolds numbers above 6500 in the Caltech Couette flow device. For suspensions with matched particle and fluid densities and solid fractions less than 40%, we find that the effective viscosity only depends on the particle solid fraction until we observe the shear-thickening behaviors for *Re* of approximately 10. For the intermediate *Re* from 10 to 100 and lower solid fractions, the effective viscosity not only depends on the particle solid fraction, but also shows increased dependence on *Re*. For *Re* greater than 100, the liquid-solid flows transition to the turbulent regime, similar to what we see for the pure fluids. At the maximum solid fraction of 50%, the magnitude of the effective viscosity has increased by a factor of 20 as compared to the results of the 10% solid fraction, but the effective viscosity is nearly independent of *Re*. A particle Reynolds number (*Re'*) based on the maximum shear flow velocity and the particle diameter is introduced to examine the effective viscosity of the suspensions. Since the present studies use particles with different sizes, *Re'* is found to be a better way to correlate the effective viscosity than the traditional *Re*. For the analysis of liquid-solid flows with a density ratio of 1.05, the effective viscosity of the particulate flow increases with the Stokes number for loading fractions of 10% and 20%, while the dependence is reversed for higher solid fractions.

Item Type: | Thesis (Dissertation (Ph.D.)) | ||||
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Subject Keywords: | Liquid-Solid Flows | ||||

Degree Grantor: | California Institute of Technology | ||||

Division: | Engineering and Applied Science | ||||

Major Option: | Aeronautics | ||||

Minor Option: | Computer Science | ||||

Awards: | Ernest E. Sechler Memorial Award in Aeronautics, 2018. Marble Graduate Fellowship, 2016. Stanback Graduate Fellowship, 2016. | ||||

Thesis Availability: | Public (worldwide access) | ||||

Research Advisor(s): | - Hunt, Melany L.
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Thesis Committee: | - McKeon, Beverley J. (chair)
- Brady, John F.
- Dabiri, John O.
- Hunt, Melany L.
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Defense Date: | 25 May 2022 | ||||

Funders: |
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Record Number: | CaltechTHESIS:06062022-033735914 | ||||

Persistent URL: | https://resolver.caltech.edu/CaltechTHESIS:06062022-033735914 | ||||

DOI: | 10.7907/5ey8-v324 | ||||

ORCID: |
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Default Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | ||||

ID Code: | 14948 | ||||

Collection: | CaltechTHESIS | ||||

Deposited By: | Yichuan Song | ||||

Deposited On: | 07 Jun 2022 15:29 | ||||

Last Modified: | 04 Aug 2022 19:27 |

## Thesis Files

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