Dear All,

I would like to simulate a mixing system. My setup is the following (also see attached picture):

• Tank: Normally the top of tank is open to the atmosphere.
• Stirrer: The stirrer is a long circular rod with 2 propellers fixed on it.
• Fluid Medium: Water for the moment

Should I set up the study as internal analysis with a lid on the water-level of my tank and define this as environmental pressure opening?

For the rotating stirrer I have created a separate part that completely encloses the stirrer and defined local rotating region @ 200 RPM.

I have tried with this setup but unfortunately the solver terminates abnormally after reporting that there is negative pressure (1.8e+81 or some sort of crazy number like that).

What do you think the problem is?

Also, would it be a good idea to define the walls of the tank as "Wall Boundaries"? Are there any goals I should set to help the solver converge? if so, what would an appropriate goal be for a general feeling of how good/bad the water is being mixed?

Any ideas or comments would be more than welcome!

Thanks in advance guys.

Best,

Xenofon