Hi there,
I'm trying to run two simple heat conduction problems, but the results are not consistent with the theoretical ones.
Case 01:
Geometry: 1 mm * 1 mm * 5 mm bar, built with AutoCAD.
format: iges
material: aluminum (generic), heat capacity = 237 (x) this is a typo
thermal conductivity = 237 (o)
type: steady state
heat load: 1 W (I suppose the unit is Watts) on a 1 mm*1 mm side area
boundary condition: temperature = 273 on the other 1 mm *1 mm side are.
Coordinate Scaling = 0.38
The result: After tuning the "Coordinate Scaling" to be 0.38, the temperature on the side where heat source is applied is 294, which is close to the handwriting calculation.
However, when I tried to run the case with only the geometry changing to 1 mm * 1 mm * 2.5 mm, Elmer gave me the result of 278, which is supposed to be 283.
Could anyone help me with this?
Heat conduction simulation result is not consistent.
Heat conduction simulation result is not consistent.
Last edited by Roy on 05 Dec 2017, 18:56, edited 1 time in total.
Re: Heat conduction simulation result is not consistent.
Hi,
a common problem in such cases is that the CAD model is using mm as length units, whereas Elmer assumes m. This can be fixed by writing
in the Simulation section (Free text field in ElmerGUI).
If that doesn't fix the problem, you could post your sif file so that someone can have a look at it.
HTH,
Matthias
a common problem in such cases is that the CAD model is using mm as length units, whereas Elmer assumes m. This can be fixed by writing
Code: Select all
Coordinate Scaling = 0.001
If that doesn't fix the problem, you could post your sif file so that someone can have a look at it.
HTH,
Matthias
Re: Heat conduction simulation result is not consistent.
Hi mzenker, thanks for replying. The problem isn't fixed; the temperature is wrong (the temperature on the surface heat source is applied is 273. ). the sif file is shown below:
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
Timestepping Method = BDF
BDF Order = 1
Solver Input File = case.sif
Post File = case.ep
Coordinate Scaling = 0.001
End
Constants
Gravity(4) = 0 1 0 9.82
Stefan Boltzmann = 5.67e08
Permittivity of Vacuum = 8.8542e12
Boltzmann Constant = 1.3807e23
Unit Charge = 1.602e19
End
Body 1
Target Bodies(1) = 1
Name = "Body Property 1"
Equation = 1
Material = 1
Body Force = 1
End
Solver 1
Equation = Heat Equation
Variable = Temperature
Procedure = "HeatSolve" "HeatSolver"
Exec Solver = Always
Stabilize = True
Bubbles = False
Lumped Mass Matrix = False
Optimize Bandwidth = True
Steady State Convergence Tolerance = 1.0e5
Nonlinear System Convergence Tolerance = 1.0e7
Nonlinear System Max Iterations = 20
Nonlinear System Newton After Iterations = 3
Nonlinear System Newton After Tolerance = 1.0e3
Nonlinear System Relaxation Factor = 1
Linear System Solver = Iterative
Linear System Iterative Method = BiCGStab
Linear System Max Iterations = 500
Linear System Convergence Tolerance = 1.0e10
BiCGstabl polynomial degree = 2
Linear System Preconditioning = ILU1
Linear System ILUT Tolerance = 1.0e3
Linear System Abort Not Converged = False
Linear System Residual Output = 1
Linear System Precondition Recompute = 1
End
Equation 1
Name = "Equation 1"
Active Solvers(1) = 1
End
Material 1
Name = "Aluminium (generic)"
Heat expansion Coefficient = 23.1e6
Heat Conductivity = 237.0
Sound speed = 5000.0
Heat Capacity = 897.0
Mesh Poisson ratio = 0.35
Density = 2700.0
Poisson ratio = 0.35
Youngs modulus = 70.0e9
End
Body Force 1
Name = "BodyForce 1"
Heat Source = 1
End
Boundary Condition 1
Target Boundaries(1) = 6
Name = "BoundaryCondition 1"
Temperature = 273
End
Does anyone know what the cause is? Is it due to the meshing or the process of importing CAD file?
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
Timestepping Method = BDF
BDF Order = 1
Solver Input File = case.sif
Post File = case.ep
Coordinate Scaling = 0.001
End
Constants
Gravity(4) = 0 1 0 9.82
Stefan Boltzmann = 5.67e08
Permittivity of Vacuum = 8.8542e12
Boltzmann Constant = 1.3807e23
Unit Charge = 1.602e19
End
Body 1
Target Bodies(1) = 1
Name = "Body Property 1"
Equation = 1
Material = 1
Body Force = 1
End
Solver 1
Equation = Heat Equation
Variable = Temperature
Procedure = "HeatSolve" "HeatSolver"
Exec Solver = Always
Stabilize = True
Bubbles = False
Lumped Mass Matrix = False
Optimize Bandwidth = True
Steady State Convergence Tolerance = 1.0e5
Nonlinear System Convergence Tolerance = 1.0e7
Nonlinear System Max Iterations = 20
Nonlinear System Newton After Iterations = 3
Nonlinear System Newton After Tolerance = 1.0e3
Nonlinear System Relaxation Factor = 1
Linear System Solver = Iterative
Linear System Iterative Method = BiCGStab
Linear System Max Iterations = 500
Linear System Convergence Tolerance = 1.0e10
BiCGstabl polynomial degree = 2
Linear System Preconditioning = ILU1
Linear System ILUT Tolerance = 1.0e3
Linear System Abort Not Converged = False
Linear System Residual Output = 1
Linear System Precondition Recompute = 1
End
Equation 1
Name = "Equation 1"
Active Solvers(1) = 1
End
Material 1
Name = "Aluminium (generic)"
Heat expansion Coefficient = 23.1e6
Heat Conductivity = 237.0
Sound speed = 5000.0
Heat Capacity = 897.0
Mesh Poisson ratio = 0.35
Density = 2700.0
Poisson ratio = 0.35
Youngs modulus = 70.0e9
End
Body Force 1
Name = "BodyForce 1"
Heat Source = 1
End
Boundary Condition 1
Target Boundaries(1) = 6
Name = "BoundaryCondition 1"
Temperature = 273
End
Does anyone know what the cause is? Is it due to the meshing or the process of importing CAD file?

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Re: Heat conduction simulation result is not consistent.
Hi
The unit of "heat source" in SI is "W/m^3".
If you want to apply a heat source on the face then use BC with "Heat Flux" the unit of which in SI is "W/m^2".
Thus if you know the total heating power you need to divide it with the volume or area, respectively.
Peter
The unit of "heat source" in SI is "W/m^3".
If you want to apply a heat source on the face then use BC with "Heat Flux" the unit of which in SI is "W/m^2".
Thus if you know the total heating power you need to divide it with the volume or area, respectively.
Peter
Re: Heat conduction simulation result is not consistent.
Hi Peter,
Thanks for figuring out what I missed. It fixed the problem.
Matthias,
Thanks for the suggestion of having "Coordinate Scale" be 0.001, it really works. The reason why I didn't get the right results is that I misunderstood the units of Elmer.
Roy
Thanks for figuring out what I missed. It fixed the problem.
Matthias,
Thanks for the suggestion of having "Coordinate Scale" be 0.001, it really works. The reason why I didn't get the right results is that I misunderstood the units of Elmer.
Roy