[aspect-devel] S40RTS and thermal boundary layers

[Rene Gassmoeller]

Hi Marie,

as far as I can see the S40RTS perturbation should not impose boundary
layers, unless there are some in S40RTS itself (but I suppose they are
subtracted from the tomography model, i.e. it is defined by subtracting
a lateral average?). Jacky and Shangxin have more experience with that,
maybe they have more insight? Another reason might be that you are
prescribing boundary temperatures at the top and bottom, which will
overlap with the initial condition in the outermost/innermost cells. Do
you see these boundary layers also in elements below the outermost
shell? Do you see them if you remove 'inner' and 'outer' from the 'Fixed
temperature boundary indicators'?

Best,
Rene


On 07/21/2016 11:28 AM, Marie Kajan wrote:
> Hey all,
>
> Quick question. I'm not sure if this is specific to how ASPECT works
> or just my chosen parameters, but I'm using the S40RTS perturbation
> with the simple compressible material model and can already see
> boundary layers in my temperature profile at the first time step. Can
> anyone tell me where these come from? Are they imposed by ASPECT due
> to my temperature boundary conditions, and how?
>
> I'll paste my parameter file minus output settings below. Thanks!
>
> Marie
>
> ---
>
> set Dimension                              = 3
> set Start time                             = 0
> set End time                               = 0
> set Linear solver tolerance                = 1e-5
> set Max nonlinear iterations               = 100
> set Nonlinear solver scheme                = iterated IMPES
> set Nonlinear solver tolerance             = 1e-5
> set Number of cheap Stokes solver steps    = 0
> set Output directory                       =
> /RQexec/mnk/aspect/output_shell_simple_3d_freeslip_s40rts_compressible
> set Use years in output instead of seconds = true
>
>
> subsection Boundary temperature model
>   set Model name = spherical constant
>
>   subsection Spherical constant
>     set Inner temperature = 4000
>     set Outer temperature = 300
>   end
> end
>
>
> subsection Discretization
>   set Use locally conservative discretization = false
>
>   subsection Stabilization parameters
>     set alpha = 2
>     set beta  = 0.117
>     set cR    = 0.5
>   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 earth-like
> end
>
>
> subsection Heating model
>   set List of model names = adiabatic heating
>
>   subsection Adiabatic heating
>     set Use simplified adiabatic heating = true
>   end
> end
>
>
> subsection Initial conditions
>   set Model name = S40RTS perturbation
>
>   subsection S40RTS perturbation
>     set Data directory                                               =
> /home/mnk/aspect-1.4.0/data/initial-conditions/S40RTS/
>     set Initial condition file name                                  =
> S40RTS.sph
>     set Remove degree 0 from perturbation                            =
> true
>     set Spline knots depth file name                                 =
> Spline_knots.txt
>     set Thermal expansion coefficient in initial temperature scaling =
> 3e-5
>     set Vs to density scaling                                        = 0.2
>   end
> end
>
>
> subsection Material model
>   set Model name = simple compressible
> end
>
>
> subsection Mesh refinement
>   set Initial adaptive refinement = 0
>   set Initial global refinement   = 4
> end
>
>
> subsection Model settings
>   set Fixed temperature boundary indicators   = inner, outer
>   set Tangential velocity boundary indicators = inner, outer
>   set Remove nullspace                        = net rotation
> end
>
>
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