The ring is a fluid body with internal diameter of 60mm, outer diameter of 80mm and height of 10mm. Since the ring was modelled in mm, I've put "Coordinate Scaling = 0.001" in the simulation section. The normal-tangential coordinate system was used to simulate the motion of the inner boundary. Some experimenting was needed to find the right variable to use (Velocity 3 = 20 in Boundary Condition 3).
After some trials and tweaking I was happy the solution converged. But looking at the results I see some strange things, which I cannot exactly understand. I think I'm missing something, because the direction of the tangential velocity seems to turn around at a random point in the circumference:
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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 = 5.67e-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
End
Solver 1
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-9
Nonlinear System Max Iterations = 20
Nonlinear System Newton After Iterations = 8
Nonlinear System Newton After Tolerance = 1.0e-3
Nonlinear System Relaxation Factor = 0.5
Linear System Solver = Iterative
Linear System Iterative Method = BiCGStab
Linear System Max Iterations = 80
Linear System Convergence Tolerance = 1.0e-11
Linear System Preconditioning = ILU2
Linear System ILUT Tolerance = 1.0e-5
Linear System Abort Not Converged = False
Linear System Residual Output = 1
Linear System Precondition Recompute = 1
End
Equation 1
Name = "Navier-Stokes Eq"
Active Solvers(1) = 1
End
Material 1
Name = "Oil, olive (25 C)"
Viscosity = 0.06
Heat expansion Coefficient = 0.72e-3
Heat Conductivity = 0.17
Sound speed = 1430.0
Heat Capacity = 1970.0
Density = 800.0
End
Boundary Condition 1
Target Boundaries(1) = 1
Name = "Outflow"
Velocity 1 = 0
Velocity 2 = 0
External Pressure = 100000
End
Boundary Condition 2
Target Boundaries(1) = 2
Name = "No-slip wall"
Noslip wall BC = True
End
Boundary Condition 3
Target Boundaries(1) = 3
Name = "RotatingWall"
Velocity 3 = 20
Velocity 1 = 0
Velocity 2 = 0
Normal-Tangential Velocity = True
End
Boundary Condition 4
Target Boundaries(1) = 6
Name = "Inflow"
Velocity 1 = 0
Velocity 2 = 0
External Pressure = 110000
End