Makes perfect sense. You'd want them to be as close to full size proportions to properly mimic the total aero effect.riff_raff wrote:aussiegman- I'm a mechanical guy and I know next to nothing about aero, but I did spend some time working for a company that built wind tunnel models for the aerospace industry. Many of the models we built were of very reduced scale since they had to fit into the small area test section of "blow-down" transonic/supersonic tunnels. The smaller the model scale, the tighter the profile tolerances became that we were asked to hold.
I've not heard of the aerospace tunnels ability to effectively "scale" apparent gas viscosity, but to a certain scale this sounds plausible.riff_raff wrote:Regarding Reynolds number and scaling effects, I recall that one or two of the more sophisticated tunnels had the ability of using a different mixture of gases (instead of compressed air) that gave more accurate test result, but I don't recall what these gas mixtures were composed of.
If you were using a small scale model in the small wind tunnels (basically rectangular perspex boxes) and the associated gas volume was low enough so you could effectively use a decent gas recirculation system then this sounds like a good solution.
I have seen very small relative scale aero models used in sealed chambers for measurements of shockwave propagation with Schlieren photography. No idea if the gas mixed or a hybrid to "scale" but there you go. Helium to nitrogen might work if it mixes properly and you get the ratio right.
However down to a certain scale, I think you would probably still run into scalability effects as the gas would eventually get to "sticky" and just not scale down any further (molecules are fixed in size after all), but i have no idea what that level may be for a given gas or gas combination or whether that threshold is so low that it wouldn't be an issue .
