. What I have in front of me is Paper No 2409 from the American Society of Civil Engineers "Diffusion of submerged Jets" by Alberston, Jensen and Hunter Rouse dated 1948 - plus written discussions by Holderson, Citrini, Bains and Henry - these papers give you exactly what you are looking for including distribution curves and formulae but I am sure you can find a simple summary in a modern text book. -