Time required for paper publication
If you consider submitting your manuscript to the OpenFOAM Journal, you can do this anytime you prefer. The OpenFOAM Journal releases papers immediately upon acceptance, we don't wait until enough paper accumulate to fill an issue.
If you want to get your OpenFOAM related results out to the community, you can start by submitting your manuscript here.
You can check out the issues in the OpenFOAM Journal here.