[HWilliams79]

I am trying to simulate an experimental set-up consisting of a liquid in a closed container with air above the container (the container is sealed so air does not leave). It is necessary to specify the pressure of the air above the container,.

A sphere is then dropped from above the liquid surface to impact on the liquid. In this set-up, given no fluid leaves the system, should the correct boundary condition be a stagnation inlet on all four walls of the container where the pressure can be specified, or is it still necessary to have an outlet?

[FliegenderZirkus]

What about only specifying the pressure as an initial condition and keeping all boundaries as walls?

[HWilliams79]

That is possible. I think StarCCM has an offset for pressure so if one sets an inlet boundary to 1 bar it is actually 2 bar atmospheric pressure.

Would the initial condition be specified by specifying a scalar function for absolute pressure?

[FliegenderZirkus]

In a simulation with the Gravity model enabled (as is probably your case?) the pressure that is specified in both boundary conditions and initial conditions is the piezometric pressure. This is described in detail in these two articles:

Explaining the pressure in a VOF simulation

What is the pressure treatment at the boundaries when gravity model is turned on?

[HWilliams79]

I do not seem to have ''permission'' to view these, is there somewhere else I can find them?

[FliegenderZirkus]

There's a chapter on this in the User manual under
Simulating Physics/Fluid Flow/Pressure
But in any case the Support Portal is very useful, I recommend trying to get access. Unless your license doesn't contain support, in which case you're left with the manual...