Learning Forum

[cem biz]

Hello, 

I am a master's student and I am trying to do a validation case for an Axisymmetric subsonic Jet Nozzle. Since I am a beginner in Ansys, although the initial case is periodic as shown below,

 I did start with the 2D case to get used to meshing and software. Then I solved the 2D case and got good results compared to NASA. Then I exported my mesh to ICEM CFD to rotate it 1 degree and solved it again with fluent (shown below)

 however, this time I couldn't perform the mesh check in the beginning, and couldn't calculate it every time I tried to calculate it gave an error below

 

Hybrid initialization is done.

 

Writing Settings file "C:\Users\bbaca\AppData\Local\Temp\WB_bbaca_19128_2\wbnew_files\dp0\FFF\Fluent\lmesh.set"...

writing rp variables ... Done.

writing domain variables ... Done.

writing fluid (type fluid) (mixture) ... Done.

writing periodic_low-face_high-face (type periodic) (mixture) ... Done.

writing high-face (type periodic) (mixture) ... Done.

writing int_fluid (type interior) (mixture) ... Done.

writing pressure-far-field (type pressure-far-field) (mixture) ... Done.

writing jet-wall (type wall) (mixture) ... Done.

writing jet-inlet (type pressure-inlet) (mixture) ... Done.

writing outlet (type pressure-outlet) (mixture) ... Done.

writing symmetry (type symmetry) (mixture) ... Done.

writing zones map name-id ... Done.

 

 

iter continuity x-velocity y-velocity z-velocity energy nut time/iter

 

===============Message from the Cortex Process================================

 

Compute processes interrupted. Processing can be resumed.

 

==============================================================================

 

Error at Node 1: Divergence detected in AMG solver

 

Divergence detected - temporarily reducing Courant number to 0.5

and trying again...

 

Divergence detected - temporarily reducing Courant number to 0.05

and trying again...

 

Divergence detected - temporarily reducing Courant number to 0.005

and trying again...

 

Divergence detected - temporarily reducing Courant number to 0.0005

and trying again...

Stabilizing Coupled to enhance linear solver robustness.

Stabilizing Coupled using GMRES to enhance linear solver robustness.

 

Divergence detected - temporarily reducing Courant number to 5e-05

and trying again...

Stabilizing Coupled to enhance linear solver robustness.

Stabilizing Coupled using GMRES to enhance linear solver robustness.

 

Error at Node 0: Divergence detected in AMG solver

Writing "| gzip -2cf > SolutionMonitor.gz"...

Writing temporary file C:\Users\bbaca\AppData\Local\Temp\flntgz-43722 ...

Done.

 

 

Calculation complete.

 

I am not sure is the mesh file is okay that's why I am attaching my mesh file as well.

https://drive.google.com/drive/folders/1MtyQbhZGmYC3-zDd5ZbaXUh3hXFnkjqk?usp=drive_link

[Rob]

I suspect the 1 degree rotation isn't helping as you'll have a very skew cell at the axis. Try with a 30 degree sector. However, unless you model the full 360 zone I'd expect 2d-axi and the 3d sector to be near enough identical. The only reason a full model may differ is when the jet isn't stable and a lack of constraints will allow it to move if it's inclined to do so. 

[cem biz]

I solved the issue by using the workbench>tool> appearance>anable beta option, created a symmetry on the meshing, and changed the type to axisymmetric on symmetry. This enabled me to have a degree with how many elements I want in between. Now it works all fine. I think importing a mesh to Ansys should be improved because I tried many ways to do it but I couldn't do it in the end. And thank you Rob, but I have to validate the case from NASA for my project, so it's not possible for me to apply any other way. Thank you for your valuable comment.