Boundary condition for free overfall.
 

Hello everyone.

I am simulating flow through pipe. In experimental setup, pipe was flowing full and freely through outlet into a tank. For numerical setup, I did two ways.

1) I used pressure outlet at end of the pipe and didn't model tank
2) I model the whole setup, so pipe outlet was treated as interior.

In both cases, I got almost same discharge from pipe outlet and both were within 10-12% of actual discharge.

My question is using the "pressure outlet" BC is correct or not for free overfall though I am getting reasonable result using that?

Thanks in advance !

Regards,
Tanjina