Short story: I am receiving the Gebhart Factor Error, and I don't know how to solve it, or even where to read about it !
How can I fix it ? Which element of the boundary condition is missing or causing this error? Where can I find multiphysic (radiation, convection and air flow) examples to learn? or what is the best way to learn this software.(I found only few videos on youtube, and they were not detailed and I couldn't extract much information from the 3 manual with a quick read, maybe it need more passes)
Long story: I'm new to Elmer (2 weeks from the first time I've heard its name); and I am starting with multiphysic problem. I am describing the main case at the end, but right now, I've tried to simplify it to learn step by step
Simplified problem:I have two intersecting cube (basically a cubic heating element inside a room) and I want to simulate heat radiation between. Unfortunately, I am receiving "Gebhardt Factor Error", but I don't know how can I fix it (believe me, I have tried every possible scenario that i knew might help, but to be honest, I don't know where or how to learn the software properly! I have downloaded three manuals, for solver, model and tutorial but ... let's say I am under pressure and I didn't read it step by step).
These are some information that might help:
CAD Image:
Screenshot of Elmer
Sif
Code: Select all
Header
CHECK KEYWORDS Warn
Mesh DB "." "."
Include Path ""
Results Directory ""
End
Simulation
Max Output Level = 5
Coordinate System = Cartesian
Coordinate Mapping(3) = 1 2 3
Simulation Type = Steady state
Steady State Max Iterations = 1
Output Intervals(1) = 1
Solver Input File = case.sif
Post File = case.vtu
End
Constants
Gravity(4) = 0 -1 0 9.82
Stefan Boltzmann = 5.670374419e-08
Permittivity of Vacuum = 8.85418781e-12
Permeability of Vacuum = 1.25663706e-6
Boltzmann Constant = 1.380649e-23
Unit Charge = 1.6021766e-19
End
Body 1
Target Bodies(1) = 1
Name = "Panel"
Equation = 1
Material = 1
Initial condition = 1
End
Body 2
Target Bodies(1) = 2
Name = "Room"
Equation = 1
Material = 2
Initial condition = 1
End
Solver 1
Equation = Heat Equation
Procedure = "HeatSolve" "HeatSolver"
Variable = Temperature
Exec Solver = Always
Stabilize = True
Optimize Bandwidth = True
Steady State Convergence Tolerance = 1.0e-5
Nonlinear System Convergence Tolerance = 1.0e-7
Nonlinear System Max Iterations = 20
Nonlinear System Newton After Iterations = 3
Nonlinear System Newton After Tolerance = 1.0e-3
Nonlinear System Relaxation Factor = 1
Linear System Solver = Iterative
Linear System Iterative Method = BiCGStab
Linear System Max Iterations = 500
Linear System Convergence Tolerance = 1.0e-10
BiCGstabl polynomial degree = 2
Linear System Preconditioning = ILU0
Linear System ILUT Tolerance = 1.0e-3
Linear System Abort Not Converged = False
Linear System Residual Output = 10
Linear System Precondition Recompute = 1
End
Equation 1
Name = "Equation 1"
Active Solvers(1) = 1
End
Material 1
Name = "Aluminium (generic)"
Sound speed = 5000.0
Heat Conductivity = 237.0
Youngs modulus = 70.0e9
Poisson ratio = 0.35
Heat expansion Coefficient = 23.1e-6
Heat Capacity = 897.0
Density = 2700.0
End
Material 2
Name = "Steel (carbon - generic)"
Youngs modulus = 200.0e9
Heat expansion Coefficient = 13.8e-6
Sound speed = 5100.0
Density = 7850.0
Heat Capacity = 1265.0
Heat Conductivity = 44.8
Poisson ratio = 0.285
End
Initial Condition 1
Name = "InitialCondition 1"
Temperature = 300
End
Boundary Condition 1
Target Boundaries(1) = 6
Name = "600 0.6"
Emissivity = 0.6
Radiation = Diffuse Gray
Heat Flux = 600
End
Boundary Condition 2
Target Boundaries(11) = 7 8 9 10 11 12 13 14 15 16 17
Name = "0.5 sides"
Emissivity = 0.5
Radiation = Diffuse Gray
End
Boundary Condition 3
Target Boundaries(5) = 1 2 3 4 5
Name = "0.6 P"
Radiation = Diffuse Gray
Emissivity = 0.6
EndZip of all generated files
https://file.io/QCtRQpJ11v4M
Clearly, I am using windows, and I have downloaded the latest zip version (gui with mpi), but there is a problem with running paraview from elmer or running post processing of elmer, which I guess it should be due the zip version without installation.
* BTW, one thing that might be the problem: I have selected the same initial thermal condition for both bodies, and there is no external or dirichlet temperature applied to the boundaries. In reality the heater and environment are at equilibrium (room temp) and heater, heats up due to its flux. I expect the elmer to understand this scenario, but maybe it is the issue ???
The original Problem
I have a heating element inside of a room and it generates a heat flux; meaning there is a big hollow cube (with thick walls), containing a cubic heater, and air.
Heater is connected to the wall, but I am excluding the conduction.
There will be heat convection, which is one of the main objectives of the simulation (both heat flow and heat transfer).
There will be heat radiation, between heat, walls and air. Yes, I know the heat transfer of a transparent material is low, but I still need it; and furthermore, I don't know how to include heated walls into the equation and consider their effect as secondary heat sources (due to heating up by the heater's radiation).
I haven't reached there yet, but I am super scared about possible problems and corners that I don't know of.