I wondered if anyone new a "simple" procedure for modeling water draining through a funnel. I would like it to be an unsteady problem where the water surface moves as it would under gravity (draining without replenishment). I am unsure if I have to specify all the boundaries as moving, and if I do, am I responsible for dictating the rate?

Thanks,

Rupp.

For simple: check Bird, Stewart and Lightfoot, "Transport Phenomena", and Munson et al, "Fluid Mechanics"

For complex: use a free-surface model like the VOF model in FLUENT. You'll have two phases: gas and liquid (water). Since the gas will be entering from the top of the funnel as the liquid level recedes, you need to specify the pressure at the boundary = Patm. This method will be able to predict (through the correct inputs) vortex formation in the liquid surface.

For more complex: use a moving mesh model. Here you prescribe the motion of the liquid surface through a complex user-defined function on the basis on the analytical solutions provided in the simple approach above

Thanks for the great tips! I am anxious to give them a go!

Rupp.