[careyprice]

Hi you awesome people, I just started learning fluent and got a few questions about simulating a tank drain process. Any help would be very much appreciated. Thank you!!

The set up is shown in the attachment.

Given:
1. 2 tanks are always filled (always overflowed).
2. Both tanks’ top surface (Red lines, Surface A and Surface B) are free surface and open to atmosphere (1atm)
3. 2 tanks are connected by a tube, which is partially immersed in tank #2.

Objective:
to find the steady state flow speed at the star position.

My questions:
1. How to define BC of A and B?
It seems my system doesn't have any inlet or outlet.....
2. Where should the operating pressure 1atm be defined (A or B)?
From reality, both A and B are at 1atm. However the flow is driven by the liquid pressure, so im confused where to put the operating pressure...

[careyprice]

Any help please??

[SJSW]

Originally Posted by careyprice

Any help please??

I think maybe you should try VOF model if you want to observe how the surface change.

[ghost82]

If the 2 tanks are always filled (i.e. the level doesn't change) I would set the top level to pressure inlet and the bottom level to pressure outlet (both atmospheric pressure).
For operating pressure take a point inside the domain.
Enable gravity and you should see fluid moving from the top to the bottom.

In your system fluid should enter from A and it should exit to B (so you have an inlet and an outlet).

Daniele