damon_rinard wrote: Good guess, but it's not the fixture drag per se, as we tare and subtract that; there are probably slightly different fixture interactions though. This is another plus for us when using CFD: Just like in real life, there's no holding fixture in CFD. (Unless we want to include it.)
Yeah, if only someone made a real-time wind sensor (speed and direction) so that these measurements could be taken outside ;-)
As for CdA, point taken. But the balance actually measures the drag force, and we report the drag force; CdA would be subsequently calculated from that, so I'm not seeing how it would allow us to compare results from different tunnels any better.
Except, drag force alone means little without the context of air density and wind speed. In other words, reporting CdA is taking that context into account and giving you a single number.
Here's the thing...if the CdA of an object isn't consistent across tunnels, then doesn't that play to the arguments of those who say that wind tunnel measurements don't reflect "reality"?
Drag force is just what we work in; my mind is more used to it (I hope that doesn't mean I'm getting old! LOL).
Of course it does :-P ...and your reasoning is the same one that is going to prevent the US from switching over to the metric system. I just saw an article on this subject just this past week...no generation wants to be the one to have to do the conversions in their head! ;-)
edit: found the blog post http://www.mobilehydraulictips.com/...the-imperial-system/