Thanks, I'd actually seen that site. I just find it difficult to believe that there isn't a relatively simple set of formulae developed to provide theoretical outwash. I mean, induced velocity is simply a function of disc loading with standard formulae for at disk and remote wake velocities. An idealized outwash velocity can't be that difficult (he says having forgotten all the math he learned that would have helped him determine it himself).
I'm just looking for something relatively simple to plug and chug out a rough order of magnitude velocity.