Characterizing and quantifying turbulent flow using magnetic resonance
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Date
2022-08
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University of New Brunswick
Abstract
“I am an old man now, and when I die and go to heaven there are two matters on which I hope for enlightenment. One is quantum electrodynamics, and the other is the turbulent motion of fluids. And about the former I am rather optimistic.” -Sir Horace Lamb, in a 1932 address to the British Association for the Advancement of Science
Fluid turbulence is found everywhere in nature and in many engineering applications. Although the equations governing turbulent flow have not yet been solved analytically, advances have been made in the measurement of this phenomenon. The aim of this work is to contribute Magnetic Resonance (MR) methodologies to the arsenal of measurement methods that can help unravel the mystery of fluid turbulence. Magnetic Resonance is well-suited to the measurement of turbulent flow because it is non-invasive. Three turbulent systems are studied in this thesis: a pipe, a pipe with a constriction, and a baroque recorder. In the recorder, velocity is measured using motion-sensitized Single Point Ramped Imaging with T1 Enhancement (SPRITE) and preliminary estimates of the degree of turbulence are extracted from this data. In a pipe with a constriction, motion-sensitized SPRITE is once again employed, but this time with motion sensitization applied along two Cartesian axes simultaneously to build up a full picture of anisotropic turbulence. The technique is akin to Diffusion Tensor Imaging which is used in clinical applications to measure fibrous tissues like the brain and muscles. In both a straight pipe and a pipe with a constriction, a new technique called Rapid Acceleration and Velocity Encoding (RAVE) is used to measure velocity and acceleration distributions. Together, these MR-based methodologies can be used to explore turbulence and hopefully shed some light on this chaotic and complicated phenomenon.