[starry09]

Before using multiple reference frames (MRF) to model a bioreactor, I took the practice just for a simplified gas sparging system.

I draw a geometry of a solid tank with an empty space for the sparging body and the surface sparging body.
Trial 6. CAD.PNG

Q1. For MRF, is this okay to subtract from the solid tank the region for sparging system or impellers? I confirmed that the solid tank without vacant spaces for the sparger was not working for simulation with this error message, 'Flow boundary zone found adjacent to solid zone.'

Q2. What should I do to get full data in reference frames? Gray region appeared that it did not have any data in contour graphing.
Trial 6.PNG

[vinerm]

You are right in saying that the solid sparger is not required. Only the fluid (you may call it solid but that is in geometric sense only) region around the sparger is required. Gray region represents the place where there are are no values for the field variables, most likely because that region belongs to a solid cell zone and not a fluid cell zone. The boundary of the fluid region itself behaves like the boundary of the sparger, ain't that anyway correct because the fluid is bounded by some solid body? So, in case you have any cell zone that is selected as solid type, then you can delete it from Fluent. Keep only the cell zone that is selected as Fluid under Cell Zone Conditions > Type.

[starry09]

Originally Posted by vinerm

You are right in saying that the solid sparger is not required. Only the fluid (you may call it solid but that is in geometric sense only) region around the sparger is required. Gray region represents the place where there are are no values for the field variables, most likely because that region belongs to a solid cell zone and not a fluid cell zone. The boundary of the fluid region itself behaves like the boundary of the sparger, ain't that anyway correct because the fluid is bounded by some solid body? So, in case you have any cell zone that is selected as solid type, then you can delete it from Fluent. Keep only the cell zone that is selected as Fluid under Cell Zone Conditions > Type.

I modified the CAD design of the fluid region (solid type) with the sparger space empty. It was working with this design, thanks.
CAPTURE2.PNGCAPTURE.PNGCAPTURE4.PNG

But as you know, if the sparger (Φ10) has a smaller hole (Φ3), how do I design the geometry?
I additionally insert a hole surface on the top area of the sparger, which, however, missed the inlet and instead can just allow for manipulating contact region.
(I previously changed the type of contact region to inlet-vent; boundary conditions>interfaces>contact region --> boundary conditions>inlet>contact region, but the momentum tab was inactivated.)
CAPTURE3.PNGCAPTURE5.PNG

[vinerm]

If the sparger has been removed, you should have only one cell zone and then there cannot be any interfaces. If you have more than one cell zone, then, you need to go back to your CAD tool and ensure that all the bodies belong to single part. Ensure that at the Ansys Meshing stage, if you are using Ansys Meshing, nothing exists in Connections. If there are contacts, delete those. There should not be any interface in your Fluent case.

Secondly, your mesh appears to be too coarse. You may have to refine it. Then, even a hole with 3 will be captured and you will be able to define it as inlet.