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Simulation with turbulence modelling converges but laminar simulation does not

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Old   December 29, 2023, 12:06
Default Simulation with turbulence modelling converges but laminar simulation does not
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Timothy
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Hi,

I've been trying to run a 2D single-phase simulation on a relatively simple geometry using Simplefoam. Convergence can be arrived at when I incorporate the use of the k-epsilon turbulence model, whether turbulence is turned on or off in the turbulenceProperties file, but when no turbulence model is used, I either run into a floating point exception or the residuals oscillate and fail to fall to the desired level.
The geometry is here: https://imgur.com/a/ErOuaUP
The boundary conditions for U are:
  • Inlet: fixedvalue, uniform (2 0 0)
  • walls: noslip
  • outlet: pressureInletOutletVelocity
The boundary conditions for P are
  • Inlet: zerogradient
  • walls: zerogradient
  • outlet: totalpressure, p0=0

The case folder is here: https://drive.google.com/drive/folde...usp=drive_link

I have tried changing the mesh resolution, reducing the timestep, changing to a fixedvalue pressure outlet BC, and decreasing the inlet velocity to lower the Reynolds number of the ingoing flow but to no avail. I would appreciate any advice or guidance regarding this.

Thank you
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Old   January 7, 2024, 10:34
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Saeed Jamshidi
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Quote:
but when no turbulence model is used
Do you mean laminar flow?

Please try this:

Code:
relaxationFactors
{
    fields
    {
        p               0.3;
    }
    equations
    {
        U               0.7;
    }
}
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Old   January 11, 2024, 14:29
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Timothy
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Thanks. Decreasing the relaxation factors by itself didn't work, but lowering the velocity and characteristic length until the flow regime was laminar (Re=2000), together with lowering the relaxation factors, worked
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