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Examining the Effect of Particle-particle and Fluid-particle Interactions on Mixing and Dispersion of Solids

Lopez, Ramon (2022) Examining the Effect of Particle-particle and Fluid-particle Interactions on Mixing and Dispersion of Solids. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Particle-fluid and particle-particle interaction play an essential role in many applications: the mixing of solids and liquids, granulation, coating, waste removal, oil production, solid rocket propellants, etc. The viscosity of the fluid can affect the efficiency of this process. For example, a high viscosity fluid needs a higher applied shear such that it is typical that a bladed mixer is used for applications such as the mixing of solid rocket propellant. As an alternative, a Resonant Acoustic Mixer (RAM) boasts several purported advantages over a bladed mixer including shorter mixing time and fewer particle breakages. Nevertheless, the mixing mechanisms and critical operational parameters that affect the mixing performance within a RAM are poorly understood. In this work, the RAM was evaluated using both experiments and computational modeling. It is found that higher viscosities decrease the mixing performance. Interestingly, size differences between particles are critical, and some cases show segregation.
Another case in which particle-fluid interactions play a vital role is in processes that involve a liquid bridge between particles. We examine the dynamics of a liquid bridge between a sphere and a flat plate being separated from each other. Unlike previous research, we focus on the case where the viscosity of the bridge is lower than that of the external fluid. We develop a lubrication theory-based model that is applicable for the general case of a viscosity mismatch between the bridge fluid and the external fluid. The model predicts that a low viscosity bridge reduces the force as compared to both separation without a liquid bridge or separation with a bridge of matched viscosity. Experiments show that the length of the bridge at rupture increases as the separation velocity increases. Also, the magnitude of the force reduction is experimentally shown to be more severe at small sphere-plate separations and at large bridge volumes, but the magnitude of the reduction is even larger than that predicted from our model. We propose that the lubricating effect of a thin coating of the low-viscosity bridge fluid that is left behind on the sphere and plate is responsible for this discrepancy.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Lopez, Ramonramonlopezotero@gmail.comrel58@pitt.edu0000-0003-3960-7291
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Thesis AdvisorMcCarthy,
Committee MemberVelankar,
Committee MemberLi,
Committee MemberPeyman,
Date: 6 September 2022
Date Type: Publication
Defense Date: 23 February 2022
Approval Date: 6 September 2022
Submission Date: 23 June 2022
Access Restriction: 1 year -- Restrict access to University of Pittsburgh for a period of 1 year.
Number of Pages: 128
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Chemical and Petroleum Engineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: RAM, mixing, liquid bridge, modeling
Date Deposited: 06 Sep 2022 16:34
Last Modified: 06 Sep 2023 05:15

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