A simple portable magnetic resonance technique for characterizing circular couette flow of non-Newtonian fluids

William Selby; Phil Garland; Igor Mastikhin

doi:10.1016/j.jmr.2022.107325

A simple portable magnetic resonance technique for characterizing circular couette flow of non-Newtonian fluids

J Magn Reson. 2022 Dec:345:107325. doi: 10.1016/j.jmr.2022.107325. Epub 2022 Nov 5.

Authors

William Selby¹, Phil Garland², Igor Mastikhin³

Affiliations

¹ MRI Research Centre, Department of Physics, University of New Brunswick, 8 Bailey Drive, Fredericton E3B 5A3, NB, Canada.
² Department of Mechanical Engineering, University of New Brunswick, 15 Dineen Drive, Fredericton E3B 5A3, NB, Canada.
³ MRI Research Centre, Department of Physics, University of New Brunswick, 8 Bailey Drive, Fredericton E3B 5A3, NB, Canada. Electronic address: mast@unb.ca.

PMID: 36370547
DOI: 10.1016/j.jmr.2022.107325

Abstract

In this work, we expand on past portable magnetic resonance flow methods and propose a novel method for characterizing circular (laminar) Couette flow of non-Newtonian fluids. Symmetry of the flow system combined with a constant magnetic field gradient leads to phase interference, affecting the signal magnitude, and net phase cancellation when averaging across the excited slice, preventing the use of phase-sensitive methods. Therefore, we utilize the dependence of signal magnitude at variable echo times and shear rates to characterize rheological properties. Theoretical equations governing the velocity distributions of fluids that obey a simple power-law model are used to obtain integral expressions for signal magnitude. Integral expressions can be simplified by approximating a thin excited slice or complete excitation of the Couette cell depending on experimental parameters. With simple data acquisition and analysis procedures employed, our measurements of the flow behavior indices of non-Newtonian xanthan gum dispersions are in close agreement with conventional rheological magnetic resonance measurements.

Keywords: Constant gradient; Couette flow; Flow behavior index; Low field magnetic resonance; Non-Newtonian fluids; Portable magnetic resonance; Rheology; Shear thinning fluids.