Is there any established physics which studies the minimal opening of containers so that its contents can flow out without jamming?
I am wondering on what characteristics of the contents this will vary, as well as on the shape of the opening. Of course the problem might become more complex when the contents are flexible or a mixture.
Perhaps this is studied in hydrodynamics, although the contents may not always be liquid? So is there any study as hydrodynamics, but which is actually related to solids (or even better: perhaps both liquids as well as solids and/or even other states)?
Very pragmatically, this is coming from what might be called an "oatmeal problem", namely: how big a hole should I cut in the corner of my oatmeal bag, not needing to cut it again when I notice the first cut wasn't sufficient to let my breakfast flow in; i.e. when the oats have stopped flowing out after the initial drop (note that pressing the bag might work somewhat but usually this will make the oats come out only very slowly).