Tuesday, March 26, 2013
More Emflume drag body testing.
Drag body testing in the Emflume. from Steve Gough on Vimeo.
(UPDATE: Blogger is mangling images; sometimes days after they're posted. We have no idea why. Working on it, sorry.)
We need a robust, inexpensive way for students to measure water velocity in our Emflume. Nothing on the market meets that need, so we have to do it.
A drag body sits in a stream of fluid, with a rod attached so force on it can be measured. The Wright Brothers were pioneers here, and what I tested today is much like what they built.
Crude? Still used in lots of research, and on the Apollo flights to measure rocket velocity. NASA researchers learned, in the 1960's, that dimpled balls -- like golf balls -- were much more stable in streams of air, and gave better readings.
Watching these instruments bounce around today I was reminded that fluid mechanics is a tough topic. That's why we need to build this flume in 2013, nearly 50 years after those NASA scientists learned that whiffle balls made good sensors.
Thanks to SIU colleagues Bill Hinz and Jim Garvey for the loan of a reference velocimeter.
Reference: Reed, Wilmer, and James Lynch. 1962. A simple fast response anemometer. (NASA Langley Research Center, Hampton, VA). Journal of Applied Meteorology.