Hi,
I have convergence problems with a steady incompressible flow (inlet, outlet and walls) and have tried the turbulence model kepsilon with different solver settings (tolerances, Linear Solvers and relaxation factors) and mesh densities.
But I have still the problem and get in the plot only a small layer of velocity at the inlet. The rest of the fluid is not moving.
Maybe someone has an idea what the problem is. I think I am setting up the whole simulation wrong.
I am using ElmerGUI with Windows 10 64bit.
Kindly regards
Markus
Navier Stokes  Incompressible Flow  keModel
Navier Stokes  Incompressible Flow  keModel
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Re: Navier Stokes  Incompressible Flow  keModel
Here is the convergence and velocitiy plot
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Re: Navier Stokes  Incompressible Flow  keModel
If it is turbulent flow than a steady state may not exist.
In that case you can use transient analysis.
Mesh size matters, it may be too coarse of a mesh.
Problem size matters, yours is 400 meters by 600 meters.
I scaled it down to 0.4 x 0.60
I meshed it coarse, I would go any coarser.
This is the last step before it diverged (13 Steady State iteration)
In that case you can use transient analysis.
Mesh size matters, it may be too coarse of a mesh.
Problem size matters, yours is 400 meters by 600 meters.
I scaled it down to 0.4 x 0.60
I meshed it coarse, I would go any coarser.
This is the last step before it diverged (13 Steady State iteration)
Re: Navier Stokes  Incompressible Flow  keModel
Hi ,
thank your for your time. The scale factor of my elmer model is correct with 0.4x0.6  the attached CAD Model (exported STEP from Salome) was wrong.
I attached the last mesh with its Density of 1.3e6 nodes and 6.9e6 elements. I think it is fine enough to get a result.
In your Model you have the same "step" of velocity at your inlet and I think this is physically not possible.
Do you really think it could be a turbulence problem with the steady state solving? If you reduce the velocity at the inlet its getting a little bit better, but its still problematic. And with this dimensions and only v_inlet=0.01 mm/s I thought it to be laminar.
In my opinion the case is equal to to the curvedPipeGUItutorial?!
I also tried to run a simulation with viscous layers at the walls (meshed through salome), but Elmer doesn´t accepted the resulting element type.
Kindly regards
Markus
thank your for your time. The scale factor of my elmer model is correct with 0.4x0.6  the attached CAD Model (exported STEP from Salome) was wrong.
I attached the last mesh with its Density of 1.3e6 nodes and 6.9e6 elements. I think it is fine enough to get a result.
In your Model you have the same "step" of velocity at your inlet and I think this is physically not possible.
Do you really think it could be a turbulence problem with the steady state solving? If you reduce the velocity at the inlet its getting a little bit better, but its still problematic. And with this dimensions and only v_inlet=0.01 mm/s I thought it to be laminar.
In my opinion the case is equal to to the curvedPipeGUItutorial?!
I also tried to run a simulation with viscous layers at the walls (meshed through salome), but Elmer doesn´t accepted the resulting element type.
Kindly regards
Markus
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 Posts: 1397
 Joined: 25 Jan 2019, 01:28
 Antispam: Yes
Re: Navier Stokes  Incompressible Flow  keModel
The velocity input is of 0.01 is 0.01 m/s. One way to test if is the flow is to use a really high viscosity, if it converges you can start decreasing it until it diverges. I believe the inlet size on the curved pipe tutorial is 0.01 m. at 0.4 m a velocity of 0.01 m/s has a Reynolds of about 3000, which is in the turbulent range, In the pipe tutorial the Reynolds number is about 100.
Re: Navier Stokes  Incompressible Flow  keModel
Yeah, I think I got it with a viscous layer mesh and some modification in the kesolver like
http://elmerfem.org/forum/viewtopic.php?p=22933
Thank you for your support .
http://elmerfem.org/forum/viewtopic.php?p=22933
Thank you for your support .
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