[aspect-devel] Aspect-devel Digest, Vol 12, Issue 3
Wolfgang Bangerth
bangerth at math.tamu.edu
Mon Nov 19 12:27:46 PST 2012
All,
I know it's terrible -- I don't recall who exactly sent me this input
file (attached) and whether I modified it, but in any case I ran it over
the weekend to see what happens to the boundary fluxes in the shell
geometry. Attached is what I get from simply running this on 16
processors for a *very* long time.
The two heat fluxes never reach a steady state -- rather, the jump up
and down every time a plume detaches from the inner or outer boundaries.
Looking at the solution picture (also attached), I'm not surprised that
the heat fluxes don't coincide: it looks like the boundary layers are
less than one cell width, and so we can not expect to resolve them
accurately. Rather, the heat flux given by these numerical
approximations is determined by the smallest length scale that can be
resolved by the mesh -- and because this length scale is different for
the inner and outer boundaries, the heat fluxes is different. (Of
course, had we chosen a mesh where the radial resolution is the same at
the two boundaries, we may have gotten results where the two heat fluxes
match -- but are both completely wrong.)
Best
W.
--
------------------------------------------------------------------------
Wolfgang Bangerth email: bangerth at math.tamu.edu
www: http://www.math.tamu.edu/~bangerth/
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set CFL number = 1.0
set End time = 1e12
set Output directory = output
set Resume computation = false
set Start time = 0
set Use years in output instead of seconds = true
set Dimension = 2
subsection Boundary temperature model
set Model name = spherical constant
subsection Spherical constant
set Inner temperature = 5000
set Outer temperature = 1
end
end
subsection Discretization
set Stokes velocity polynomial degree = 2
set Temperature polynomial degree = 2
set Use locally conservative discretization = true
subsection Stabilization parameters
set alpha = 2
set beta = 0.078
set cR = 0.11
end
end
subsection Geometry model
set Model name = spherical shell
subsection Spherical shell
set Inner radius = 3481000
set Outer radius = 6371000
end
end
subsection Gravity model
set Model name = radial constant
subsection Radial constant
set Magnitude = 9.81
end
end
subsection Initial conditions
set Model name = spherical hexagonal perturbation
end
subsection Material model
set Model name = simple
subsection Simple model
set Reference density = 3300
set Reference temperature = 273
set Thermal conductivity = 4.1
set Thermal expansion coefficient = 4e-5
set Viscosity = 1e22
set Composition viscosity prefactor = 1.
set Density differential for compositional field 1 = 1000.
end
end
subsection Mesh refinement
set Additional refinement times =
set Initial adaptive refinement = 0
set Initial global refinement = 5
set Refinement fraction = 0.0
set Coarsening fraction = 0.00
set Strategy = Temperature
set Time steps between mesh refinement = 1000000
end
subsection Model settings
set Fixed temperature boundary indicators = 0,1
set Include shear heating = false
set Include adiabatic heating = false
set Prescribed velocity boundary indicators =
set Radiogenic heating rate = 0e0
set Tangential velocity boundary indicators = 1
set Zero velocity boundary indicators = 0
end
subsection Compositional fields
set Number of fields = 0
end
subsection Postprocess
set List of postprocessors = visualization, heat flux statistics
subsection Visualization
set Number of grouped files = 1
set Output format = vtu
set Time between graphical output = 1e7
set List of output variables = density,partition,viscosity
end
end
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