[Nickolay]

Hi everyone!

I kindly ask for your help as I seem to be stuck with my simulation since several weeks.

The accumulator is 10,5 m height and is fulled up to the 8.5 meter with water. The upper pipes are at level 7,5m. I set up the inputs and outputs as Mass Flow Rate in the Setup.

The first calculation results showed about water and air volume fractions between 0 and 1 between the 8. and 9. meter and that air is pumped out from the upper side.

Unfortunately those results can't be correct for the real model.

So... I tried several things:

1) mesh deformation - can't use because I have 2 domains (pipes and material);

2) bigger mesh - went too big for the computer parameters;

3) less bigger mesh - got "poor quality mesh" error messages;

4) Refinement options - don't got exactly the desired mesh.

It would be great if I could make the finest mesh for the model at level 8m or do fine to less fine mesh from the dome to the base.

I kindly ask you for your help. You can reach me also per e-mail.

Thank you in advance!

[Kina]

I suppose you are not using ICEM but regular Ansys Meshing.
what is the point in using a deforming mesh in your case? can you post a picture of the geometry? it's kinda hard for me to imagine.
Have you tried local refinements such as a sphere / body of influence or contact refinement or face meshing?

[Nickolay]

Thank you Alex for your reply.

You can see pictures of my geometry and mesh in my next posts.

We have a big cylindrical body (our heat accumulator) with height of 10,4 m and diameter of 11,3 m. There are 8 horizontal pipes, who all "come" from different directions , continue through the body space and all end at 1,5 m from the center (XY plane).

At the height of 1,5 m there are 2 inlets and 2 outlets. (XZ plane)

At the height of 6 m there is one inlet. (XZ plane)

At the height of 7,5 m there are one inlet and two outlets. (XZ plane)

In our current result we get from 8 to 9 m area with volume fraction of water fraction decreasing from 1 to 0.

But we get air fractions in the outlet pipes, which is impossible in our existing model.

I am using regular Ansys Meshing and got finer mesh using the eight pipes as bodies of influence, but it would be best for this simulation to do a refinement at the height of 8 meters.

Another option would be to do the mesh fine to less fine from the upper to the bottom part.

Thank you again for the support.

[Nickolay]

This is another picture of my geometry.

[Nickolay]

This is the default mesh.

[Nickolay]

Those are the volume fraction from our results.

[Kina]

thank you for the pictures. since you use the pipes as bodies of influence I assume, you are working in assembly tetra meshing. the results do not look logically indeed. if you think, mesh refinement could help solve the problem, you can also define bodies of influence that can have any shape and don't necessarily have to belong to your assembly. Just draw a big box (the boundaries of the refinement) in your tank in design modeler and extrude it as frozen body. Now you can define it with local element sizing as body of influence and it will not be recognized as real body by fluent. this is how i did this example.

[Nickolay]

Thank you for your kind answer, Alex!

I'll try this and hope it would make my life a bit easier.

[Nickolay]

Using the eight pipes as body of influence I made a successful mesh that seems to be suitable for further work.

I am now trying to get a closer look at it. Could you tell how a cross-section look can be done. It would be of great help for me.

[Kina]

So you refined the entire mesh instead of just refining the important part with a frozen body of influence. This gives you accurate results but with a partial refinement you save computation time. The cross sectional view is the blue logo in the middle of your toolbar. Looks like a blue body that is cut by a black line. Also, you can look for cut-plane or clip-plane in the help section. One should be for design modeler, the other one for cfd post. I can't try it out right now since I am on vacation.

[Nickolay]

Thanks again for your support!