Hello everyone,
I am trying to use a Compositing material model to include batch melting and latent heat of melting into a model with viscoplastic rheology.
It is a simple testing case that should represent decompression melting beneath and extending lithospheric plate. The viscosity looks fine and decompression melting occurs as well, but I am confused by the latent heat. In the visualization output, the latent heat is non-zero even if there is zero melt fraction. What is the source of this heat?
Thanks in advance for your help!
Petra
Here is the PRM file:
set Dimension = 2
set Use years in output instead of seconds = true
set Output directory = output-extension-freesurf-latentheat
set End time = 2e6 #years
set Nonlinear solver scheme = single Advection, iterated defect correction Stokes
set Nonlinear solver tolerance = 1e-5
set Max nonlinear iterations = 100
subsection Geometry model
set Model name = box
subsection Box
set X repetitions = 2
set Y repetitions = 1
set X extent = 100e3
set Y extent = 50e3
end
end
subsection Mesh deformation
set Mesh deformation boundary indicators = top: free surface
subsection Free surface
set Surface velocity projection = vertical
end
set Additional tangential mesh velocity boundary indicators = left, right
end
set Pressure normalization = no
subsection Gravity model
set Model name = vertical
subsection Vertical
set Magnitude = 10.0
end
end
subsection Initial temperature model
set Model name = function
subsection Function
set Variable names = x,y,t
set Function constants = Ttop=273, Tbot=1473, ysize=50e3
set Function expression = Ttop+(Tbot-Ttop)*(ysize-y)/ysize
end
end
subsection Boundary temperature model
set Fixed temperature boundary indicators = top, bottom
set List of model names = function
subsection Function
set Function constants = Ttop=273, Tbot=1473, ysize=50e3
set Function expression = (y>ysize/2 ? Ttop : Tbot)
end
end
subsection Boundary velocity model
set Prescribed velocity boundary indicators = bottom y: function, left x: function, right x: function
subsection Function
set Variable names = x,y
set Function constants = v=0.02, xsize=100e3, ysize=50e3
set Function expression = (x<xsize/2 ? -v : v); (y<ysize/2 ? ysize/xsize*v : -ysize/xsize*v)
end
end
subsection Compositional fields
set Number of fields = 2
set Names of fields = pyroxenite, weak_seed
set Compositional field methods = field, field
end
subsection Initial composition model
set List of model names = function
subsection Function
set Variable names = x,y
set Function constants = xsize=100e3, ypos=30e3, rad=5e3
set Function expression = 0; if((x-xsize/2)^2+(y-ypos)^2<rad^2, 1, 0)
end
end
subsection Boundary composition model
set Fixed composition boundary indicators = top, bottom, left, right
set List of model names = initial composition
end
subsection Heating model
set List of model names = latent heat
end
subsection Material model
set Model name = compositing
set Material averaging = harmonic average only viscosity
subsection Compositing
set Viscosity = visco plastic
set Density = visco plastic
set Thermal expansion coefficient = visco plastic
set Specific heat = visco plastic
set Thermal conductivity = visco plastic
set Compressibility = visco plastic
set Entropy derivative pressure = latent heat melt
set Entropy derivative temperature = latent heat melt
set Reaction terms = latent heat melt
end
subsection Latent heat melt
set A1 = 841.32
set A2 = 1.3463e-7
set A3 = -5.3158e-18
end
subsection Visco Plastic
set Densities = 2800 # kg/m3
set Thermal diffusivities = 1e-6
set Heat capacities = 1000
set Thermal expansivities = 0
set Viscous flow law = dislocation
set Prefactors for dislocation creep = 2.7e-18, 1, 1e-15
set Activation energies for dislocation creep = 480e3
set Activation volumes for dislocation creep = 1.1e-5
set Stress exponents for dislocation creep = 3.5
set Angles of internal friction = 10.0, 1, 9.0 # degrees
set Cohesions = 10e6 # Pa
set Minimum viscosity = 1e19 # Pa s
set Maximum viscosity = 1e25 # Pa s
end
end
subsection Mesh refinement
set Initial global refinement = 4
set Initial adaptive refinement = 2
set Time steps between mesh refinement = 1
set Strategy = composition, strain rate
set Refinement criteria merge operation = max
set Refinement criteria scaling factors = 1, 2
end
subsection Postprocess
set List of postprocessors = visualization
subsection Visualization
set Time steps between graphical output = 1
set Output mesh velocity = true
set List of output variables = material properties, strain rate, heating, melt fraction
subsection Material properties
set List of material properties = density, viscosity
end
end
end
