[lorenzoalari]

Hi everyone,
I am a new user, eager to learn as much as possible from all of you :-)

I am facing a problem which is causing me some troubles.
My goal is to estimate the flow rate through a vertical pipe connected to a tank, simulating the emptying of the latter. So, basically it's a gravity problem with 0 pressure on the free surface of the oil and on the discharge section of the nozzle. I employed a viscous-laminar model with energy activated. Gravity is of course enabled. Even though I should use a transient solution, it requires way too long for the solution to converge (for all the oil in the tank to drain). Hence I studied the problem with a steady approach. I specified all the oil properties in the materials section, writing them as functions of temperature.

What I'd like to know is:
- how do I deal with the Bussinesque's parameters? If I do not check the "operating density" box in the cell zone condition, the solution converges at the very first iteration, providing me zero flow rate. If I check that box, which density should I give as input?
- Should I specifically express the zero-pressure location in the "cell zone conditions" menu even though I've already specified the pressure inlet/outlet in the boundary conditions?

Ciao,
Lorenzo

Edit: for the sake of completeness, I think it can be useful to say that I got a solution but it does not match the experimental data: the flow rate I obtain is half of the experimental one.