CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

Comparison of OF and Fluent results

Register Blogs Members List Search Today's Posts Mark Forums Read

Like Tree1Likes
  • 1 Post By Tobermory

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   December 3, 2021, 09:15
Default Comparison of OF and Fluent results
  #1
New Member
 
Aydar
Join Date: Dec 2021
Location: Russia, Kazan
Posts: 4
Rep Power: 4
Aydar Mukhametov is on a distinguished road
Hi everyone!
I want to move from calculations in Fluent to the OF. To do this, we compared the results obtained in both programs.

Problem: turbulent flow in a circular channel.
Fluent boundary conditions:
k-w SST turbulence model;
SIMPLE solver scheme;
Inlet velocity 10 m/s;
Turbulence intensity at inlet and outlet 4%;
Pressure outlet 0 Pa.
Geometry:
Circular cross-section channel,diameter 0.1 m, length 100D.
Symmetry on XY, ZX.

The mesh was created in Ansis meshing and transferred to OF via "Fluent3DMeshToFoam"
The first case of the mesh with y+=1 was with the warning "Failed 1 Mesh Checks" and the calculations did not coincide.
The second case with a mesh with y+=94 completely coincided with Fluent.
Mesh.jpg
log_mesh1.txt
log_mesh2.txt

OpenFoam bc:
setupOF_1.zip
k, w, vel, nut same to Fluent.

Please tell me where the error is or why the rough mesh matches the results. What boundary conditions should be set for the mesh with y+=1.
Aydar Mukhametov is offline   Reply With Quote

Old   December 3, 2021, 09:18
Default continuation
  #2
New Member
 
Aydar
Join Date: Dec 2021
Location: Russia, Kazan
Posts: 4
Rep Power: 4
Aydar Mukhametov is on a distinguished road
Obtained data
omega-axis fine mesh.png
omega-axis rude mesh.png
Vel_profile_axis_r.PNG
v-axis fine mesh.png
v-axis rude mesh.png
__________________
Best regards,Mukhametov Aydar
Aydar Mukhametov is offline   Reply With Quote

Old   December 4, 2021, 10:28
Default
  #3
Senior Member
 
Join Date: Apr 2020
Location: UK
Posts: 735
Rep Power: 14
Tobermory will become famous soon enough
The mesh check is telling you that the max cell aspect ratio is too high (1922) for your y+=1 mesh ... this can screw up the gradient calculations, since the wall normal gradient component of a variable is so much larger than the streamwise gradient component simply due to the cell dimensions. This means that the solution can decouple, which is maybe what you are seeing.

You can try using something like the leastSquares gradScheme approach which helps counter this, but in reality the best solution is, as ever, to just improve your mesh. If you want to minimise your cell count then just grab the near wall cells that have aspect ratios above 100 and use refineMesh to refine them in the axial direction; you'll need several nested refinements to get the near wall cell ARs down to around 100. That should then help.

Good luck!
Aydar Mukhametov likes this.
Tobermory is offline   Reply With Quote

Reply

Tags
fluent, openfoam, turbulance, wall boundary condition

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On



All times are GMT -4. The time now is 12:19.