I had the need to calculate eductor performance several years ago and couldn't find any software on the market that was any help. Several of the vendors had bits and pieces specific to their equipment, but nothing generalized. From the e-Mails I get on the subject at work I would say that the situation has not changed. My solution in 1995 was to go to the literature looking for information on downhole jet pumps (Oil & Gas term). I found a couple of very useful old documents (1960's vintage) that pointed me towards the underlying arithmetic that I was then able to adapt to eductors. It worked and now I have a bunch of them running and have sized many more for use by my company on wells around the world. The best article was in "Oil World" as I recall.
Sorry, but my company won't allow me to post the key equations on this forum, but it wasn't that tough to adapt the jet pump equations.