Our wind tunnel is driven by a WWII P-38 prop and a big electric motor. I think it can generate wind speeds up to around 100 mph. It recirculates the air and takes up 2/3rds of a pretty large room, but is surprisingly quiet. It is in the attic of what used to be the hangar. Back in the early days of my dept. (1930's) they actually designed, built, and worked on real aircraft. There are some cool pictures floating around that show the hangar with the Akerman tailless plane. Someday I want to build a scale model of that and fly it (perhaps autonomously.) It would be a fun and challenging project and would be a tip of the hat to our building's name sake, and his airplane that never really had a chance to fully fly. We have the original blue prints but I'm still trying to get a copy of them. Among other things, this is one of the reasons I started creating MAdesigner (madesigner.flightgear.org) ... as a tool to help design and build complicated wing structures based on logical (or higher level) design parameters.
https://www.aem.umn.edu/info/history/akerman.shtmlIf anyone decides to build their own wind tunnel, *PLEASE* post pictures and tell us about your project. I think it would be very interesting.