[aspect-devel] AGU meeting feedback

[Juliane Dannberg]

Hi all,

On 01/09/2014 05:53 PM, Timo Heister wrote:
>> - Second, what happens if we use a smooth field, say using an arctangent
>>    with a width of 2-3 cells. I bet that the first peak is exactly where
>>    it was before, whereas the second one suddenly becomes grid 
>> independent.
> Yes, I think so too. I am somewhat swamped right now, so I anybody
> wants to try this out...
>
> In the long run we should find a way to get this smoothing behavior
> automatically (this is basically what a levelset reinitialization
> would do). This assumes that this fixes the problem we are seeing.
>
okay, so I just tried this and it looks quite well
I have attached a plot of root mean square velocity in dependence of 
time for different meshes, and now the solution seems not longer to be 
mesh-dependent and the second peak seems to converge to a value similar 
to the one in the van Keken Benchmark, too. I also attached my input 
file, in case anybody wants to do some more testing. In principle I just 
used a hyperbolic tangent function to smooth the boundary between the 
compositional fields.

Cheers,
Juliane
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############### Global parameters
# We use a 3d setup. Since we are only interested
# in a steady state solution, we set the end time
# equal to the start time to force a single time
# step before the program terminates.

set Dimension                              = 2
set Start time                             = 0
set End time                               = 2000
set Use years in output instead of seconds = false
set CFL number                             = 1.0
set Output directory                       = van_Keken_8_smooth

subsection Geometry model
  set Model name = box
  subsection Box
    set X extent  = 0.9142
    set Y extent  = 1.0000
  end
end

subsection Model settings
  set Include adiabatic heating               = false
  set Include shear heating                   = false # default: true
  set Tangential velocity boundary indicators = 0,1
  set Zero velocity boundary indicators       = 2,3
end

subsection Material model
  set Model name = simple
  subsection Simple model
    set Reference density             = 1010
    set Viscosity                     = 1e2
    set Thermal expansion coefficient = 0
  end
end

subsection Gravity model
  set Model name = vertical
  subsection Vertical
    set Magnitude = 10
  end
end


############### Parameters describing the temperature field
# As above, there is no need to set anything for the
# temperature boundary conditions.

subsection Boundary temperature model
  set Model name = box
end

subsection Initial conditions
  set Model name = function
  subsection Function
    set Variable names      = x,z
    set Function constants  = pi=3.14159
    set Function expression = if((z>0.2+0.02*cos(pi*x/0.9142)),0,1)
  end
end


############### Parameters describing the compositional field

subsection Compositional fields
  set Number of fields = 1
end

subsection Compositional initial conditions
  set Model name = function
  subsection Function
    set Variable names      = x,z
    set Function constants  = pi=3.14159
    set Function expression = 0.5*(1+tanh((0.2+0.02*cos(pi*x/0.9142)-z)*10/0.2))
  end
end

subsection Material model
  subsection Simple model
    set Density differential for compositional field 1 = -10
  end
end

############### Parameters describing the discretization

subsection Mesh refinement
  set Initial adaptive refinement        = 0
  set Strategy                           = composition
  set Initial global refinement          = 8
  set Time steps between mesh refinement = 1000000
  set Coarsening fraction                = 0.05
  set Refinement fraction                = 0.3
end


##subsection Discretization
##  set Composition polynomial degree = 2
##  subsection Stabilization parameters
##    set beta  = 0.5
##    set cR  = 1e15
##  end
#3end



############### Parameters describing the what to do with the solution

subsection Postprocess
  set List of postprocessors = visualization, velocity statistics, composition statistics
  subsection Visualization
    set List of output variables = all
    set Output format                 = vtu
    set Time between graphical output = 100
  end
end
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