Abstract
This research looks to develop and validate a coupled rheometry and nuclear magnetic
resonance (Rheo-NMR) system in order to investigate the rheology of complex fluids such
as drilling muds.
The work presented in this research focuses on three key areas: creation of a control software
for the custom Rheo-NMR system, development and validation of the rheometry hardware
and lastly integration of rheometry and NMR systems for simultaneous measurements. The
control software is written in python and provides the user with an interactive graphical user
interface that allows for the execution of semi-customisable experiment sequences. The design
of the rheometry system includes a motor-gearbox-transducer assembly which acts as the
drivetrain and a Taylor-Couette shear geometry. Assessment of the rheometer design involved
analysing and addressing any misalignments present in the system, calibrating and evaluating
the performance of the in-line torque transducer and lastly characterising the tribological
properties of the materials comprising the rotation point of the geometry. Validation of the
rheometer included the measurements of both Newtonian and non-Newtonian fluids. The
viscosity measurements for the Newtonian standards tested were found to agree with the
manufacturer quoted values, exhibiting a maximum measurement error of 6%. Flow curves
of non-Newtonian fluids were measured and compared to measurements from a commercial
rheometer. The power law index n derived from the results were found to agree with
measurements from the commercial rheometer. However, a notable disparity was observed
in the measured stress possibly arising from the startup conditions that affect the microstructure
differently within the shear domain of the custom and commercial rheometers.
Prior to velocimetry and simultaneous torque measurements, the linearity of the gradients
was first assessed using static 1-dimensional images obtained by magnetic resonance imaging
(MRI). Subsequently, the linearity of the phase-gradient relationship was evaluated by
considering errors due to background gradients and the velocity distribution within the MRI
image arising from the curvature of the rheometer geometry. Finally, tandem measurements of
torque and velocimetry are conducted on a non-Newtonian fluid. Local flow curve derived from
velocimetry measurements agree with the global flow curve thereby validating the quantification
of rheological properties using the Rheo-NMR system.