Learning Forum

[simone01]

Hello,

I'm trying to simulate the fluid dynamics in a 3D mixing tank.

I chose to use the multiple reference frame instead of the Sliding Mesh approach because MRF is less resource demanding than SM and give satisfactory result for these cases according to the literature and according to the ansys guide (since the impeller-baffle interactions are relatively weak, large-scale transient effects are not present and the MRF model can be used in mixing tank).

I have divided the domain into two regions: a static zone and a rotating zone (MRF zone) contaning the impeller.

I have seen from the guide and in the literature that the rotating zone should have a diameter between the impeller and the baffles.

But specifically, what size should it have? How can I determine the size in the absence of experimental data?

Thanks 

Best Regards

[DrAmine]

Just give a diameter which will enclose the impeller plus bit more. There are several videos and papers referring to mixing tank.

[DrAmine]

You can even use that as parameter for sensitivity analysis.

[simone01]

Thanks for the reply.

That was precisely the problem: I have already seen several videos and papers referring to mixing tanks and they use very different sizes of the rotation zone, but none of them justifies the choice. I have already done some simulation and I have seen that varying the size of the rotating zone the results are certainly different. I think that without experimental data it is difficult to do sensitivity analysis.

Thanks

Best regards

[DrAmine]

Yes, that is true but you can report what you are numerically observing. I would assume that with sliding mesh approach one would get less differences.

A good guess is to have at least 3 to 4 cells on each side of the connecting interface /interior.