advection_reaction.base.prm

#########################################################
# This is a benchmark case that tests the operator split
# solver scheme, which can use a different time step to
# compute reactions between compositional fields than
# the time step used for advection.
# In comparison to the example 'exponential_decay', the
# initial comosition depends on x, and there is a constant
# horizontal velocity. The composition decays over time,
# following the equations for exponential decay with a decay
# rate that depends on y.

set Additional shared libraries = ./libadvection_reaction.so

############### Global parameters

set Dimension                              = 2
set Start time                             = 0
set End time                               = 1
set Use years instead of seconds           = false

# We use a new solver scheme option that enables the operator split.
set Nonlinear solver scheme                = single Advection, single Stokes
set Use operator splitting                 = true
set Maximum time step                      = 1

# As we split the time-stepping of advection and reactions,
# there are now two different time steps in the model:
# We control the advection time step using the 'Maximum time step'
# parameter (for easy comparison with the exponential decay test
# case), and the reaction time step using the 'Reaction time step'
# parameter. We will vary both parameters in different model runs.
subsection Solver parameters
  subsection Operator splitting parameters
    set Reaction time step                 = 0.0005
  end
end

subsection Discretization
  subsection Stabilization parameters
    set beta  = 0.0
    set cR = 0.0
  end
end

subsection Geometry model
  set Model name = box

  subsection Box
    set X extent = 1
    set Y extent = 1
  end
end

subsection Compositional fields
  set Number of fields = 1
end

# The velocity on all boundaries is prescribed to a constant
# value, leading to horizontal flow from left to right.
subsection Boundary velocity model
  set Prescribed velocity boundary indicators = 0:function, 1:function, 2:function, 3:function

  subsection Function
    set Variable names      = x,z,t
    set Function constants  =
    set Function expression = 0.01;0.0
  end
end

# We then choose a vertical gravity model and describe the
# initial temperature with a vertical gradient. The default
# strength for gravity is one. The material model is the
# same as before.
subsection Gravity model
  set Model name = vertical
end

# For this model, we choose a sinusoidal initial temperature
# and composition, so that we can see how the field changes
# over time as it is advected and decays over time.
subsection Initial temperature model
  set Model name = function

  subsection Function
    set Variable names      = x,z
    set Function constants  = pi=3.1415926
    set Function expression = sin(2*pi*x)
  end
end

subsection Initial composition model
  set Model name = function

  subsection Function
    set Variable names      = x,z
    set Function constants  = pi=3.1415926
    set Function expression = sin(2*pi*x)
  end
end

subsection Boundary temperature model
  set Fixed temperature boundary indicators   = 0
  set List of model names = ExponentialDecayBoundary
end

subsection Boundary composition model
  set Fixed composition boundary indicators   = 0
  set List of model names = ExponentialDecayBoundary
end

# We choose material and heating models that let temperature
# and composition decay over time, and that is implemented in
# a plugin.
subsection Heating model
  set List of model names = exponential decay heating

  subsection Exponential decay heating
    set Half life = 10
  end
end

subsection Material model
  set Model name = exponential decay

  subsection Exponential decay
    set Half life = 10
  end

  subsection Composition reaction model
    set Thermal conductivity          = 0
    set Thermal expansion coefficient = 0
    set Viscosity                     = 1e5
    set Density differential for compositional field 1 = 0
  end
end

subsection Mesh refinement
  set Initial adaptive refinement        = 0
  set Initial global refinement          = 5
  set Time steps between mesh refinement = 0
end

subsection Postprocess
  set List of postprocessors = composition statistics, visualization, ExponentialDecayPostprocessor

  subsection Visualization
    set Time between graphical output = 0
  end
end