[aspect-devel] S40RTS and thermal boundary layers

Austermann, Jacqueline jaustermann at fas.harvard.edu
Fri Jul 22 08:28:47 PDT 2016

Hi Marie,

Just to chime in on this, my first thought is the same as Rene’s: I would think that you see "boundary layers" because you prescribe an inner and outer temperature that is very different from the adiabatic reference temperature within the mantle (and the S40RTS perturbations are very small compared to those boundary layer jumps). To check whether that’s the case you can look at the output and / or not impose these temperature boundary conditions … i.e. exactly what Rene said. S40RTS does not include boundary layers in itself, it’s only a perturbation to the depth dependent temperature profile. I also wanted to add that Shangxin fixed a bug in the normalization of the S40RTS initial condition during the hackathon so it might be worth updating your branch to the newest developer version of aspect.


On Jul 22, 2016, at 12:47 AM, Rene Gassmoeller <rene.gassmoeller at mailbox.org<mailto:rene.gassmoeller at mailbox.org>> wrote:

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'?


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!



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

subsection Discretization
  set Use locally conservative discretization = false

  subsection Stabilization parameters
    set alpha = 2
    set beta  = 0.117
    set cR    = 0.5

subsection Geometry model
   set Model name = spherical shell

  subsection Spherical shell
    set Inner radius = 3481000
    set Outer radius = 6371000

subsection Gravity model
  set Model name = radial earth-like

subsection Heating model
  set List of model names = adiabatic heating

  subsection Adiabatic heating
    set Use simplified adiabatic heating = true

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

subsection Material model
  set Model name = simple compressible

subsection Mesh refinement
  set Initial adaptive refinement = 0
  set Initial global refinement   = 4

subsection Model settings
  set Fixed temperature boundary indicators   = inner, outer
  set Tangential velocity boundary indicators = inner, outer
  set Remove nullspace                        = net rotation

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