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Graduate:
University of Oregon, Oregon
Masters Thesis: Fluid resonance in elastic-walled englacial transport networks
Abstract (upcoming publication): Englacial water transport is an integral part of the glacial hydrologic system, yet the geometry of englacial structures remains largely unknown. In this study, we explore the excitation of fluid resonance by small amplitude waves as a probe of englacial geometry. We model a hydraulic network consisting of one or more tabular cracks that intersect a cylindrical conduit, subject to oscillatory wave motion initiated at the water surface. Resulting resonant frequencies and quality factors are diagnostic of fluid properties and transport geometry. For a single crack-conduit system, the fundamental mode involves gravity-driven fluid sloshing between the conduit and the crack, at frequencies between 0.02-10 Hz for typical glacial parameters. Higher frequency modes include dispersive Krauklis waves generated within the crack and tube waves in the conduit. But we find that crack lengths are often well constrained by fundamental mode frequency and damping rate alone for settings that include alpine glaciers and ice sheets. Branching crack geometry and dip, ice thickness, and source excitation function help define limits of crack detectability for this mode. In general, we suggest that identification of eigenmodes associated with wave motion in time series data may provide a pathway towards inferring englacial hydrologic structures.
Figure showing simulated time evolving pressures and resulting frequency spectra in a conduit-crack system due to surface perturbations:
Caption: Excitation of resonant modes from different source-time functions in a three crack system where the cracks are at depths of 40 m, 90 m and 150 m. All other model parameters are the same as previous experiments and assuming fully developed flow. Left column: A long wavelength Gaussian excitation, with a scaled wavelength of 130 m. A. Forcing function for the long wavelength model run. D. Spatial time series for the long wavelength model run. G. Frequency spectra for the long wavelength model run showing the DFT of time series taken at 20 m, 65 m and 120 m. Middle column: A short wavelength excitation, with a scaled wavelength of 10 m. B. Forcing function for the short wavelength model run. E. Spatial time series for the short wavelength model run. F. Frequency spectra for the short wavelength model run showing the DFT of time series taken at 20 m, 65 m and 120 m. Right column: A simulated white noise continuous excitation, comprised of 2000 sine waves with random initial phase and a small amount of numerical noise. A. Forcing function for the continuous forcing model run. D. Spatial time series for the continuous forcing model run. G. Frequency spectra for the continuous forcing model run showing the DFT of time series taken at 20 m, 65 m and 120 m.
Figure showing how we apply our models to infer englacial structure:
[embeddoc url=”https://blogs.uoregon.edu/mcquillan/files/2020/10/couplecontours2.pdf” download=”all” viewer=”google”]
Caption: Predicting fracture length using the measurable frequency and quality factor for a coupled oscillation involving gravity-driven fluid sloshing between the conduit and the crack for geometric parameters relevant to both alpine and ice sheet environments. A. and B. Frequency contours for R = 0.1 m and 0.5 m, and L = 100 m and 1000 m. C. and D. Quality factor contours for R = 0.1 m and 0.5 m, and L = 100 m and 1000 m. In all panels, there is a transition of dominant driving forces where frequency and quality factor lose their dependence on fracture length. B. in particular shows no frequency variation for crack lengths above the 0.06 Hz (red) and 0.02 Hz (blue) contour.
For more information keep an eye out for our upcoming publication…
Measuring the viscosity of martian-like brine solutions at low temperatures
Worked to measure the viscosity of brine solutions at low temperatures (down to – 80 degrees C) for application to martian ice lenses. Viscosities of solutions of NaCl, MgCl, and Mg/ Ca perchlorates were measured using a TA instruments Rheometer.
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Undergraduate:
University of Saint Thomas, Minnesota
Data Processing of Interacting Galaxies
University of St. Thomas
2014-2015
The goal of this project was to understand galaxy evolution through interacting galaxies. We focused on NGC 3310 and NGC 2798-2799. Through this project I developed data processing skills using Python involving integration of multiple sub processes from PyRAF, SExtractor and AstroImageJ. Results of this project were a pipeline for processing data from the HDI 0.9m telescope at Kitt Peak. After the data were processed, we discovered a previously undocumented tidal loop around NGC 3310, likely indicating collisional history.
Investigating Periodic Structures in the Slow Solar Wind
Society of Physics Students/NASA Goddard Space Flight Center Heliophysics Intern
2015-2016
The goal of this project was to understand how periodic structures in the slow solar wind were created. My contribution to this goal was creating a MATLAB routine that produced multiple visual aids to track solar wind from the Sun to the Earth. Outputs of this routine were prominent periodicities in the solar wind along a specified trajectory, a movie of the solar wind traveling from the Sun to the Earth with the specified trajectory highlighted throughout the movie, multiple interactive comparison plots of solar wind density structures along multiple specified trajectories.
Construction of a High Vacuum System
University of St. Thomas
2016-2017
The goal of this project was to build a versatile high vacuum. My contributions to this project were machining supporting components, assisting in the design and construction of the main chamber, and preparing the roughing pump system for operation.