Learning Forum

[daha]

Hello Everyone

I am new to Ansys Fluent and am trying to set up a transient fluid simulation to determine the natural convection and temperature inside the cavity of a hollow sphere in hot airflow (see schematic below).

[Rob]

What wall condition have you got on the sphere? It should be coupled and you'll need to look at running the solver in transient mode. n

[daha]

Hi Rob, nThank you for taking a look at my issue! Please excuse my late reply, but better late than never... nThe solver is running in transient mode. Regarding the boundary condition of the wall I was not sure what to choose. I tried it by defining it as solid and having the wall modeled and meshed. Unfortunately, this resulted in the blue circle. I am not quite sure how to deal with this, since for example many tutorials show exhaust mainfolds where the walls are meshed too, but the result shows the temperature distribution in the walls. nFurthermore, I also just tried to just define a circle as internal air bubble, without having physically defined the wall. I then would define the wall at the boundary in the fluent setup. Unfortunately, this also did not succeed. nI am quite confused by now on what to change. Maybe I just have a configuration error somewhere else... Not quite sure how to proceed.nnDo you have any tipps? I am looking forward to any help I can get... n

[Rob]

What is the wall condition between the outer fluid and solid (wall) or inner fluid (if you use a thin surface). You model should work, and I've done this application before for pipelines. How long did you run for? n

[daha]

nI tried some further configurations, here one with symmetry. The interface wall and its shadow are set to coupled.nOne thing which I am a bit confused in the picture below is the lower temperature of the airflow after the sphere, while the sphrere itself does not get heated. Could it be that I somewhere missed to set a checkbox or something which gives the sphere a constant temperature?nThank you very much for your support!nn

[DrAmine]

List your zones, model settings, material properties, steady/unsteady, gravity...n

[daha]

Here is a list with the setup of the last of my tries (3D, using symmetries):nMaterials: nAluminium (provided by Ansys, no change)nAir (provided by Ansys, no change)nnCell Zone Conditions:nBoundary Conditions:nSolution Setup:nnIn case you would need further information, please let me know!nThank you for taking the time to help men