VOF: Gravity-Driven Flow
This tutorial demonstrates how to set up a gravity-driven flow problem in Simcenter STAR-CCM+. It simulates two-dimensional gravity-driven compressible flow through a channel connecting two chambers.
The geometry is shown below. Initially, the chamber on the left is filled with water; the one on the right and the connecting channel with air. All boundaries are solid walls except for the horizontal top left surface where a constant (atmospheric) static pressure is applied.

Under the action of gravity, water flows into the right chamber under assumed turbulent conditions. At the same time, water also flows in through the top left boundary to maintain a constant fluid level. The pressure in the right chamber increases due to the air compression, resulting in a reduction of the flow rate through the pressure boundary. After some time, all fluid elements are at rest and in a hydro-static equilibrium.