Aero-Dynamic Lubrication?

[CraigD]

Some unsolicited suggestions and ideas for folk experimenting with air flows:

• Smoke is useful. Try injecting smoke from a lit cigarette, punk, etc, into your contraptions to visualize (ie: make visible) laminar and turbulent airflow.
  
• Terminology-wise, a device to assure that all of the air in a wind tunnel is moving in more-or-less the same direction is called a collimator (its use in aerodynamics is less common than in optics). “Laminar” (“layered”) refers to air moving at different speeds in the same direction remaining parallel. It’s usually of most interest when one of the layers of air is contacting some surface, in which case it’s called a boundary layer, but you’ve got another significant case of it where the fast-moving, roughly cylindrical body of air emerging from a ducted or unducted fan meets the still surrounding air.
  
• The main purpose of the collimator in a wind tunnel is to eliminate artifacts, particularly the rotating effect of the driving fan. Try holding a model airplane in front of a fan, and the need for this is obvious – the plane will try to roll fast.
  
• Square or hexagonal grids made of paper, plastic, metal, or thin wood are, I think, better for a wind collimator than packed together straws. I suspect you’re getting some pretty complicated turbulence from those straws. The only wind tunnel I ever built, from plans from Estes (the model rocket company) published in the 1970s, used glued-together paper milk cartons.
  
• Fan duct length and taper can be optimized for a given medium (eg: ambient/ humidity/temperature/pressure air) and fan. An example of this is the design of the bypass duct on a turbofan jet engine.
  
• Blowing out a candle doesn’t necessarily require a large volume of air, or even any net air movement. One of my childhood toys was a sort of pistol with a strong spring-powered piston that drove air through a tapered plastic chamber to a small (about 2 cm) nozzle. One of its tricks was that it could blow out a candle at an amazing distance, 3 meters or so if I recall correctly, even though it expelled only a fraction of a liter of air in a single shot. It also could damage eardrums when discharged directly into an ear (or so legend had it – I never tried that trick), which is why, I suspect, it’s no longer a popular toy.
  A Mythbusters episode demonstrated blowing out flames (ultimately a big gas flame) with little rubber diaphragms and loudspeakers.
  

[alexander]

ooh i just had an idea of how to produce the contraption for the car :rolleyes:

 

ok, i take clay and model the duct structure, surrounded by a can, grease up the dried clay or putty (i have yet to investigate what would work best) but take a bunch of industrial hot glue sticks (they are thicker and have ratings on hardness of plastic) melt a package of those together in a pot and then poor the plastic mixture into the mold, shake it a little bit to expell any air that may be in the mold, let set, remove the mold (hopefully that will work), trim and i should have a test-ready mold, ready for installation in a car or device i want to use.... at the cost of sactificeing a pot, i think i will start with making a mold... gotta stop at some artist store an pick up some clay of some sort... i may need some sort of an enamel, or something to keep the plastic from sticking to the mold.... anyone have any ideas? i think this way would be easier then creating hexagons from paper probably more reliable for real testing, too?

[Turtle]

ooh i just had an idea of how to produce the contraption for the car :) ...ok, i take clay and model the duct structure, surrounded by a can, grease up the dried clay or putty (i have yet to investigate what would work best) but take a bunch of industrial hot glue sticks (they are thicker and have ratings on hardness of plastic) melt a package of those together in a pot and then poor the plastic mixture into the mold...

 

Now we're cookin'! The holt-melt glue mold idea is interesting and it's in the back of my mind now for future use.

 

Some unsolicited suggestions and ideas for folk experimenting with air flows:

-Smoke is useful. Try injecting smoke from a lit cigarette, punk, etc, into your contraptions to visualize (ie: make visible) laminar and turbulent airflow....

 

 

I'm stocking up on the Nag Champa as we type. :doh: I think the other variations you mention are great, and give other experimenters more options for materials at hand as well as providing new results for comparisons to other designs. :smart:

 

Beisdes using the candle blow-out in initial tests, I have in mind to hang an array of ribbons/string as a target and so be able to 'see' the shape of the stream as it disturbs them.

 

I have the second row of straws nearly installed in the can, and because the straws aren't all from the same place (I scavenged them over the last few months from my roommates who eat out), they do not closepack as does the ideal theoretical model. Still, I have used straws before to build one of these for water and with good results. (threw it away in a minimalist multifunctionistic binge. :eek: )

 

In building these, I have noticed they have unusual accoustic properties, and I intend to affix a speaker in the fan end at some point and experiment with that. (The speaker will replace the fan, not add to it). There are some disorienting/interesting visual properties as well I've noticed when trying to look through the array of channels and that will get a look sooner or later.

 

Great ideas fellas, and I'm off like a dirty sock to watch some glue dry.

[alexander]

-Smoke is useful.

from my history with smoke, it can be a little hard to work with it, i mean last time when i set off a smoke bomb in my friend's shed as an april fools joke, it took us 2 hours to get back into the shed....(it was not well vented)

 

 

neighbors were like "do you want us to call the fire dep-t?", i was like "naaw, don't worry, i only used 600g of [ce]{KNO3}[/ce] to 400g of sugar, it finished burning a long time ago and i set it on a big piece of sheet metal, this is just the smoke that is left over....", my friend was like "you are one sick m&*3r f#&^$r". But hey, it was pay back time :)

 

[ce]{KNO3}[/ce] took a little long to get, had to order it and wait for it to come in, then had to poor the smoke bomb in stages, like get one batch all nice and cooked, poor it, go to next batch.... it was funny though :hihi:

[Turtle]

from my history with smoke, it can be a little hard to work with it, i mean last time when i set off a smoke bomb in my friend's shed as an april fools joke, it took us 2 hours to get back into the shed....(it was not well vented)

 

I was thinking dry ice might work to good effect?

 

Here's a snapshot of my construction so far. :doh:

[Pyrotex]

LOL,...Now, if one was to build such a plane where the engines were located in such a posistin that they provided substantial thrust of air over the fusilage even while the plane/flying machine was at rest relative to the ground, would it, could it fly, and even maybe hover?...

Well... yes.

Mississippi State University, back in the 70's I think, built such a plane.

It had two engines, one on each wing. The wings themselves came straight out of the fusilage, then curved in a semi-circle (down and then up) and ended in a second straight section at the tips.

 

The engines were mounted at the axis of the semi-circular wing sections, and each had a propeller that pushed all its air "through" the semi-circular wing section.

 

With engines revved to max, about ~90% of plane's weight was gone. The plane only needed to move forward at about ~40 mph to take off.

 

Can't find a picture online. And all numbers are guesstimates.

[Turtle]

Well... yes.

Mississippi State University, back in the 70's I think, built such a plane.

It had two engines, one on each wing. The wings themselves came straight out of the fusilage, then curved in a semi-circle (down and then up) and ended in a second straight section at the tips.

 

The engines were mounted at the axis of the semi-circular wing sections, and each had a propeller that pushed all its air "through" the semi-circular wing section.

 

With engines revved to max, about ~90% of plane's weight was gone. The plane only needed to move forward at about ~40 mph to take off.

 

Can't find a picture online. And all numbers are guesstimates.

 

Is this it? Fly me to the Moon... :doh:

Mississippi State University XAZ-1

 

Mississippi State University XV-11A Marvel

 

Mississippi State University XV-11A Marvel

 

PS Found some more pictures, but they are all the single engine deal. Perhaps the twin-engine job was black-ops and that's why we can't find photos?

XV-11A Marvel

[Turtle]

Some unsolicited suggestions and ideas for folk experimenting with air flows:

• Terminology-wise, a device to assure that all of the air in a wind tunnel is moving in more-or-less the same direction is called a collimator (its use in aerodynamics is less common than in optics). “Laminar” (“layered”) refers to air moving at different speeds in the same direction remaining parallel. ...
  
• Square or hexagonal grids made of paper, plastic, metal, or thin wood are, I think, better for a wind collimator than packed together straws. I suspect you’re getting some pretty complicated turbulence from those straws.
  
• A Mythbusters episode demonstrated blowing out flames (ultimately a big gas flame) with little rubber diaphragms and loudspeakers.
  

 

Collimator it is.

 

The (only) other cross-sectional shape that tiles the plane regularly is the equilateral triangle. Keeping all else constant in the experiment, the collimator alone suggests dozens if not hundreds of experiments wherin the cross-sectional shape is altered, the relative size of those shapes (small vs. large), the length of the collimator, and the distance the collimator is positioned away from the fan.

 

The Mythbusters are chuckle-heads I wouldn't trust to light a match. :doh:

[CraigD]

I wondered, if a person was do build a design correctly to create a plante that flies itself.

 

Lift is created by gaining speed through the air to create motion etc, and allow the air to pass over the wing structure to create the lifting effect etc...

Now, if one was to build such a plane where the engines were located in such a posistin that they provided substantial thrust of air over the fusilage even while the plane/flying machine was at rest relative to the ground, would it, could it fly, and even maybe hover?

…

Whats the thoughts on this wild idea lol.

Though wild, this is far from a new idea – such designs appear to predate the first successful powered aircraft in the early 20th century!

 

There are whole classes of aircraft that direct their prop (or jet) wash over their wings to shorten their takeoff distances. To some extent, nearly all high-performance STOL aircraft use the approach, typically with unusually large wing flaps near their props (the de Havilland Twin Otter likely having logged the most passenger-miles)

 

For sheer wild-looking-ness, my favorite class are the “deflected slipstream” variety, some of which were so extreme that they were actually capable of vertical takeoff. This paper (1 MB PDF) has a better history than any I’ve read before, and lots of diagrams and photos.

 

The success of the Rolls Royce jet VTOL aircraft, culminating in the famous Harrier, pretty much put an end to serious interest in this approach, though it figures in moderation into the design of many modern light and light commercial airplanes. Later lift fan designs like the F-35 go even further away from the “driving engine as lifting engine” approach.

Now, if one was to build such a plane where the engines were located in such a posistin that they provided substantial thrust of air over the fusilage even while the plane/flying machine was at rest relative to the ground, would it, could it fly, and even maybe hover?

As a question of practical aerodynamics, I don’t think this is possible, because if you built an airplane able to generate enough airflow over its wings while standing still on the ground, the resulting forward thrust would be so great that it would be impossible to prevent it from accelerating forward once its landing gear left the ground. You could angle it upward to prevent any forward motion, but at this point you’re describing essentially a tailsitter VTOL, which doesn’t require lifting wings at all.

 

No mention of tailsitters would be complete without a decent reference to the almost-built-in-1945 Focke-Wulf Triebflügel, IMHO the wildest-looking seriously designed airplane ever.

[InfiniteNow]

It had two engines, one on each wing. The wings themselves came straight out of the fusilage, then curved in a semi-circle (down and then up) and ended in a second straight section at the tips.

 

The engines were mounted at the axis of the semi-circular wing sections, and each had a propeller that pushed all its air "through" the semi-circular wing section.

 

Sounds a bit like the condor:

 

 

 

 

If not, you could always check here:

 

Raspet Flight Research Laboratory

[Pyrotex]

Well, guys, I searched and searched for the twin-engine STOL that I saw in a college newsletter back when I was going to school at MSU. Can't find a trace. The single engine version graciously provided by Turtle is, I believe, a successor to the clunky version I remember. Thanks.

[Turtle]

Well, guys, I searched and searched for the twin-engine STOL that I saw in a college newsletter back when I was going to school at MSU. Can't find a trace. The single engine version graciously provided by Turtle is, I believe, a successor to the clunky version I remember. Thanks.

 

Road trip to MSU Library? :D In the looking I did to find the Marvel, I found that it not only used the ducted fan, but the wing tops had active suction holes that smoothed the flow over the wing at low speed for greater lift. The ol' reverse air hockey technique.

 

Here's one of my favorite odd ball aerodynamic designs: :) >> Forward-Swept Wings

 

Meantime, the work on my collimating duct is going fine but slow. Because I started laying up in rings from the outside in, the pattern is neither type of close packing of cylinders, but a combination. I have 3 rings done, and I am counting as I go so I can get the total at the end without the madness of all those circles. :doh: Here's the duct now from the fan side. :hyper: :hihi:

[Pyrotex]

Just make sure you keep all your ducts in a row.

 

Pyro

[Turtle]

Just make sure you keep all your ducts in a row.

 

:hihi: Pyro

 

Roger that. :Bump2::wave::);) :D

 

I have been saving the straws for months, and it's looking like I have too few. :( :eek: I have 59 in the first ring, 53 in the second, and 48 in the third: total 160. I'll use what I have and make another test run on the candle.

 

Here's a drawing of the water version I made. I packed the straws friction tight & without glue, and so they tended to shift around. :)

 

[Turtle]

Ring #4 complete: 42 straws: 2 monkeys

 

Average straw diameter is 9/32".

[Turtle]

I have run out of straws, just a few short of completing the 5th ring of collimators. :D No worries; I'll just hurry up & slow down until I get more.

 

Here's the test run of the duct on the fan blowing out the test candle. I measured the maximum distance at 6.5 feet; better than the empty duct, not as good as the fan alone. Notice the change in sound from the other runs. :doh:

 

YouTube - Laminar Flow Experiment - 5 Collimator Rings http://www.youtube.com/watch?v=eQAZto5qw7o

[Turtle]

I have run out of straws, just a few short of completing the 5th ring of collimators. :( No worries; I'll just hurry up & slow down until I get more.

 

I completed the collimators in the duct today. Total of 322, 4" straws in roughly 11 rings. Photo below. :) Test runs to follow. ................... :)