### Help for a simple CFD test case (NAN when running solver))

Posted:

**24 Mar 2017, 23:31**Hello, I'm desperately trying to run my first own test case:

It's a pipe filled with water (actually I'm using the "cylinder_in_channel.iges" from the Elmer samples directory) with:

- a no-slip boundary condition on side walls and the square obstacle (Boundary Condition 1)

- no boundary conditions on inlet and outlet faces

- a body force along the axis of the pipe

and I'm aiming for a steady state solution with the Navier-Stokes and K-Epsilon solvers

I think I'm missing something obvious, but I can't find what is it.

Here my .sif file:

If someone can point me any suggestion or problem in the sif file, it would be infinitely appreciated.

Thanks to the Elmer Team and all contributors for providing this beautiful piece of free software ♡＾▽＾♡

It's a pipe filled with water (actually I'm using the "cylinder_in_channel.iges" from the Elmer samples directory) with:

- a no-slip boundary condition on side walls and the square obstacle (Boundary Condition 1)

- no boundary conditions on inlet and outlet faces

- a body force along the axis of the pipe

and I'm aiming for a steady state solution with the Navier-Stokes and K-Epsilon solvers

I think I'm missing something obvious, but I can't find what is it.

Here my .sif file:

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
Timestepping Method = BDF
BDF Order = 1
Solver Input File = case.sif
Post File = case.ep
End
Constants
Gravity(4) = 0 -1 0 9.82
Stefan Boltzmann = 5.67e-08
Permittivity of Vacuum = 8.8542e-12
Boltzmann Constant = 1.3807e-23
Unit Charge = 1.602e-19
End
Body 1
Target Bodies(1) = 1
Name = "Body 1"
Equation = 1
Material = 1
Body Force = 1
End
Solver 3
Equation = K-Epsilon
Procedure = "KESolver" "KESolver"
Exec Solver = Always
Stabilize = True
Bubbles = False
Lumped Mass Matrix = False
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 = Diagonal
Linear System ILUT Tolerance = 1.0e-3
Linear System Abort Not Converged = False
Linear System Residual Output = 1
Linear System Precondition Recompute = 1
End
Solver 2
Equation = Navier-Stokes
Procedure = "FlowSolve" "FlowSolver"
Variable = Flow Solution[Velocity:3 Pressure:1]
Exec Solver = Always
Stabilize = True
Bubbles = False
Lumped Mass Matrix = False
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 = Diagonal
Linear System ILUT Tolerance = 1.0e-3
Linear System Abort Not Converged = False
Linear System Residual Output = 1
Linear System Precondition Recompute = 1
End
Solver 1
Equation = Result Output
Output Format = Vtk
Procedure = "ResultOutputSolve" "ResultOutputSolver"
Output File Name = case
Exec Solver = Always
End
Equation 1
Name = "FluidEquations"
Active Solvers(3) = 3 2 1
End
Material 1
Name = "Water (room temperature)"
Viscosity Model = K-Epsilon
Viscosity = 1.002e-3
Heat expansion Coefficient = 0.207e-3
Heat Conductivity = 0.58
Relative Permittivity = 80.1
Sound speed = 1497.0
Heat Capacity = 4183.0
Density = 998.3
End
Body Force 1
Name = "BodyForce 1"
Flow Bodyforce 1 = 1
End
Boundary Condition 1
Target Boundaries(1) = 2
Name = "wall"
Normal-Tangential Velocity = True
Noslip wall BC = True
End
```

Thanks to the Elmer Team and all contributors for providing this beautiful piece of free software ♡＾▽＾♡