Spectral properties of homogeneous magnetohydrodynamic turbulence
dc.contributor.advisor
Berera, Arjun
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dc.contributor.advisor
Smillie, Jennifer
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dc.contributor.author
McKay, Màiri Elise
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dc.contributor.sponsor
Engineering and Physical Sciences Research Council (EPSRC)
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dc.date.accessioned
2019-08-27T09:24:29Z
dc.date.available
2019-08-27T09:24:29Z
dc.date.issued
2019-11-26
dc.description.abstract
Magnetohydrodynamics (MHD) is the study of how an electrically-conducting
fluid interacts with a magnetic field. Many of the constituents of the universe
possess a magnetic field and MHD has applications ranging from geophysical
flows to solar and galactic physics; in fact, the possible generation of magnetic
fields due to early-universe phase transitions makes MHD a valuable tool even
in cosmology. From a more practical point of view, liquid metals, such as those
required in nuclear fusion reactors, can be described by the MHD equations.
In this thesis various aspects of homogeneous, incompressible MHD without a
mean magnetic field are explored. This stripped-back setting facilitates the
development of deeper knowledge of the fundamental energy transfer mechanisms
of MHD turbulence. A complementary set of numerical and analytical results are
presented, which explore the consequences of the fundamental interactions in
MHD.
First of all, the results of high-resolution direct numerical simulations of MHD
subject to three different forcing functions are analysed in order to determine
whether or not the method of energy injection affects the behaviour of the
fields. Next, energy transfers between different length scales are computed and
compared in cases with differing values of magnetic and cross helicity, with a
view to understanding their influence on reverse energy transfer. The effect of
the magnetic Prandtl number is studied in detail by varying both the kinetic and
magnetic Reynolds numbers in decaying turbulence with initially large values of
magnetic helicity. This allows us to distinguish large magnetic Prandtl number
effects from large magnetic Reynolds number effects and small kinetic Reynolds
number effects.
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dc.identifier.uri
http://hdl.handle.net/1842/36078
dc.language.iso
en
dc.publisher
The University of Edinburgh
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dc.relation.hasversion
M. Linkmann, A. Berera, M. McKay, and J. J ager. Helical mode interactions and spectral transfer processes in magnetohydrodynamic turbulence. J. Fluid Mech., 791:61{96, 2016.
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dc.relation.hasversion
M. Linkmann, G. Sahoo, M. McKay, A. Berera, and L. Biferale. Effects of magnetic and kinetic helicities on the growth of magnetic fields in laminar and turbulent flows by helical Fourier decomposition. Astrophys. J., 836(1):26, 2017.
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dc.relation.hasversion
M. F. Linkmann, A. Berera, W. D. McComb, and M. E. McKay. Nonuniversality and finite dissipation in decaying magnetohydrodynamic turbulence. Phys. Rev. Lett., 114:235001, 2015.
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dc.relation.hasversion
M. E. McKay, A. Berera, and R. D. J. G. Ho. Fully-resolved array of simulations investigating the influence of the magnetic Prandtl number, 2018. arXiv:1806.10202.
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dc.relation.hasversion
M. E. McKay, M. Linkmann, D. Clark, A. A. Chalupa, and A. Berera. Comparison of forcing functions in magnetohydrodynamics. Phys. Rev. Fluids, 2:114604, 2017
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dc.subject
magnetohydrodynamics
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dc.subject
planetary magnetic field
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dc.subject
magnetohydrodynamic turbulence
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dc.subject
MHD equations
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dc.subject
Prandtl number
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dc.subject
Reynolds number effects
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dc.title
Spectral properties of homogeneous magnetohydrodynamic turbulence
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dc.type
Thesis or Dissertation
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dc.type.qualificationlevel
Doctoral
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dc.type.qualificationname
PhD Doctor of Philosophy
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