View Full Version : Bizarre Question
Jane-DoH
16th Feb 2011, 04:54
I was wondering that during the 1930's and 1940's when the United States had no supersonic wind-tunnels; was it possible to test a model at supersonic speed by mounting the model on a huge propeller and spinning it at a sufficient RPM?
You got the speed fast enough you'd get supersonic tip-velocities and if you were doing this for test purposes, thrust wouldn't be a desired goal.
zerozero
16th Feb 2011, 05:25
Perhaps the model would in fact reach supersonic speeds, but if there's no way to *observe* or *collect* data, then it's a worthless exercise.
There's a bizarre answer for you.
:8
Brian Abraham
16th Feb 2011, 08:22
What they did and how they did it.
Research in Supersonic Flight and the Breaking of the Sound Barrier (http://history.nasa.gov/SP-4219/Chapter3.html)
Piltdown Man
16th Feb 2011, 08:45
Thanks Brian, that was a really good read. What was really eye-opening was that this research was either corporately or officially sponsored. You can't help but wonder if this sort of research is done nowadays?
PM
mike-wsm
16th Feb 2011, 09:13
23 minutes to read all that??? It's gonna take me more like 23 hours!!! :ok:
Ex Cargo Clown
16th Feb 2011, 14:04
I don't quite know why you would mount it on a prop. You'd have all manner of other forces acting, centripetal etc plus the prop itself would ruin any chance of any kind of analysis.
A supersonic wind tunnel isn't a difficult thing to achieve theoretically, it just requires high pressure gas, and a control of pressure. Realistically it's a right pain, because you need a very high pressure to get the necessary gas velocity.
Tinstaafl
16th Feb 2011, 17:55
You can also change the air temperature in the wind tunnel to adjust M1
Jane-DoH
18th Feb 2011, 01:43
Ex Cargo Clown
I don't quite know why you would mount it on a prop.
The idea would be in days that a supersonic wind-tunnel didn't exist you could still get a supersonic tip velocity by spinning a sufficiently large diameter prop fast enough with a model on the tip
You'd have all manner of other forces acting, centripetal etc plus the prop itself would ruin any chance of any kind of analysis.
The prop would produce interference effects? Would the model need to be curved (to form the shape of the edge of the prop disc to deal with the fact that it would be spinning rather than going straight) or not?
A supersonic wind tunnel isn't a difficult thing to achieve theoretically, it just requires high pressure gas, and a control of pressure. Realistically it's a right pain, because you need a very high pressure to get the necessary gas velocity.
To some extent I understand how a supersonic wind-tunnel works. Convergent/Divergent with slots in the area where the model is to avoid shockwaves from bouncing off the walls of the tunnel and messing up the readings.
Ever considered a job with NASA? Oh OK I see you are an enthusiast and not formally engaged. Thats a good thing because you can see things that others can't.
Jane-DoH
19th Feb 2011, 02:35
DERG
Ever considered a job with NASA?
Well, when I was a kid I wanted to be an astronaut, but otherwise, no.
you can see things that others can't.
What things do I see that others don't?
Others see negativity whilst you see opportunity, in other words, your mind is not constrained..thats a good thing.
clunckdriver
19th Feb 2011, 11:25
During the early days of the CF105 Arrow {Canadas TSR2} They fired rockets across one of our large lakes with models of the aircraft mounted on the pointy end, using then state of the art transmitters data was collected by the base station . These models are now the subject of several searches by various SCUBA dives, dont think they have found one yet.
twochai
19th Feb 2011, 13:32
During the early days of the CF105 Arrow {Canadas TSR2} They fired rockets across one of our large lakes with models of the aircraft mounted on the pointy end, using then state of the art transmitters data was collected by the base station
At deHavilland Canada the need for speed on advanced aero research did not require rocket science!
http://i278.photobucket.com/albums/kk89/twochai/OtteronCradle.jpg
This would work well I think. These deHavillands look wonderful.
Landroger
21st Feb 2011, 20:44
Never mind supersonic research, that DeHavilland can only be designed to fly sloooooooooowwwwwwwwwwly. :eek: Wow! The 'barn door' flaps on big airliners always amaze me, but those jokers are huuuuge! :D
Would all that be an experimental rig for blown flaps? With prop wash it would practically be VTOL. :rolleyes:
ROger.
twochai
22nd Feb 2011, 02:00
At this point, the flap was only blown by prop wash, I believe!
I presume the purpose of the rig was to confirm actual pitching moments, pre-first flight. I'll try to find out from somebody who knows later this week.
Tinstaafl
22nd Feb 2011, 18:03
Jeez, with flaps that size I wonder if it would need a larger tailplane volume to handle pitching moments &/or reduced IAS? I wonder if it could even maintain level flight. The drag would be enormous!
Jane-DoH
22nd Feb 2011, 22:56
It looks like that plane was meant to takeoff and land in very very short distances and at very low speeds...
yes..mainly on lakes in Canada
Landroger
23rd Feb 2011, 09:08
yes..mainly on lakes in Canada
Very shallow ones? :D
Roger.
CliveL
24th Feb 2011, 07:02
">At this point, the flap was only blown by prop wash, I believe!
I presume the purpose of the rig was to confirm actual pitching moments, pre-first flight. I'll try to find out from somebody who knows later this week.
In the 1960s (I think) DeHC were interested in STOL. I think this was a non-flying testbed to examine deflected slipstream effects. Mounted on a frame to get the aircraft out of ground effects and with that grid painted on the fin it looks as if they were measuring downwash effects over the tailplane.
Here is the flying version.
http://i1080.photobucket.com/albums/j326/clivel1/2262LA.jpg (http://www.pprune.org/%3Ca%20href=)">
LANDROGER yes..you mean the long legs hahah..I see...missed that:)
Up in the NW Territories there are some really beautiful lakes and down in MN also...not to mention those fiercesome Great Lakes of the Mid West or Lake Hood in AK.
This airplane is iconic. I would love to own one. I bet there are many memories of these in Canadas' history.
Then of course in winter the floats helped with the ice. A really wonderful machine.:)
forget
24th Feb 2011, 10:05
Then of course in winter the floats helped with the ice.
Got any examples of that? :hmm:
Oh yeah forget...
Well there is tha Canada goose...
Then you got your snow waffles..you know those things..look like tennis rackets..
Then you got your Fat Alberts with the skates and the rocket boosters..
You got your big paws on your dogs for sleigh work...
Your got your skis on your scoobeedoos...
not to mention your langlauf kit..almost foergot that
Has to be more examples..maybe you can think of a few..
mike-wsm
1st Mar 2011, 19:55
Flaps blown by prop wash - I can recall the Breguet 940, 941 and 941S, the Ryan VZ-3 Vertiplane and the VZ-5 Fairchild Fledgling. Then the jet versions, the two Coanda machines, Boeing C-14 and Antonov An-72/74. Then there was the McDonnell Douglas YC-15 where the jet efflux blew over the flaps, leading eventually to the C-17.
Here is the French Breguet 941 with flaps fully extended into the slipstream and flying in a markedly nose-down attitude.
http://aerostories.free.fr/appareils/Br941/Br941_02.JPG