Aero-Dynamic Lubrication?

[arkain101]

Quote from wikipedia.

Coandă effect

Demonstration

If one holds the back of a spoon in the edge of a stream of water running freely out of a tap (faucet), the stream of water will deflect from the vertical in order to run over the back of the spoon. This is the Coandă effect in action.

 

This demonstration is the combination of the Venturi effect and the Coandă effect. The Venturi effect would cause a drop in pressure between the spoon and the stream of water, which would then be drawn towards the spoon. Once the surface of the stream hits the spoon, the Coandă effect keeps it running over the convex surface.

 

I had a chuckle when I read this. Due to the fact that I had in my own doing discovered this effect and anaylised its phsyics and found an application for it.

So there is the bernoulli principle

and

Coandă effect

 

I find there are some differences between the two.

 

Anyone want to cleary point them out to save some time?

[arkain101]

Quote from wiki on coanda effect.

Lift from an airfoil

Some people have attempted to explain how a wing generates lift, by invoking the Coandă effect. However, this theory does not produce quantifiable data, and so it is unable to predict such things as the thickness of the boundary layer. Professional aerodynamicists regard this theory as a fallacy. For example, the theory states that air “sticks” to the surface because of its viscosity. This implies that if the viscosity of the fluid changes, the amount of lift an airfoil produces should change in proportion. Experiments show that the amount of lift produced by a real wing is independent of viscosity over a wide range. The real Coandă effect requires turbulence, so it occurs only if the viscosity is sufficiently low. Furthermore, the air speeds up above a wing's upper surface. The theory assumes that the relative air-flow meets the wing at the same velocity as in free air and then follows the curve. This understates the pressure gradients by an order of magnitude.

 

This is why I created a topic here that better and seemed to re-explain lift. The topic went somewhat overlooked.

-its here, http://hypography.com/forums/physics-mathematics/4735-topic-concerning-lift.html?highlight=lift

 

I said and stand by, lift is created from the angular momentum of the mass of the air swinging around the curve of the wing. The air is glued to the wings surface from a low pressure enviroment in the atomosphere above the wings sufact. The air wants to get thrown away, but the vacuum is keeping it attatched, and the air is forced to trade places with the wing, the air gets pulled down by the wing, and the wing gets pulled up. The greater the vacuum and exhange of mass the greater the lifting effect.

 

This is flight explained. And using this data, a wing could be very much differently designed. It could have a smooth thing knife edge front, that slowly curves upwards and then more dramatically curves downards below the height of the wings front. The bottom of the wing shape would remain flat, and grooved or such to create a less drag enviorment, then slightly just curve downwards to meet with the top of the wing, like a fixed flap, although just enough to match the velocity, power, lift, and drag specs regarded to fusilages needs.

 

The same as a rocket going into space by exchanging mass from exhaust and the rocket body. The mass of the fuel/exhaust gasses being accelerated out of the rocket causes a trade in momentum where the rocket goes up and the fuel goes down, or in other words, opposite directions.

 

In the same manner a wing grabs air or a fluid and throws it downwards like the rocket (without creating much drag). The exhange in mass and momentum causes the wing do get thrown up relative to how much mass of the air is thrown down.

[Qfwfq]

An early example of aerodynamic lubrication is the golf ball. Surprisingly, it shows that the overall drag can, in certain cases, be less with turbulent flow than with laminar.

 

I also have a vague memory, from some 30 or so years ago, of a missile design emloying a small, flat circular plate to create a shock wave all around the craft. I imagine it reduced drag but ran into various engineering troubles.

[CraigD]

I also have a vague memory, from some 30 or so years ago, of a missile design emloying a small, flat circular plate to create a shock wave all around the craft. I imagine it reduced drag but ran into various engineering troubles.

This sounds a bit like the “aerospike” found on compact missiles like the US’s sub-launched Trident. From what I’ve read, the feature was successful, and did good things for the performance of the missile (if “good” is an appropriate term for a nuclear weapon :hihi: ) They’ve been around since the late 70s, and, according to the wikipedia article, are expected to be around past 2020.

[Qfwfq]

Trident could be it, yeah.

[Turtle]

I have started...er...picked back up :eek: construction of an experimental laminar flow fan duct. This is not an engine for any propulsion , rather a tool for experimenting with the effects of low velocity laminar flow in air.

 

In this video I show the duct during the installation of the first row of straws. When complete, the duct is fully packed. 12Volt auto fan, coffee can, drinking straws, masking tape & the cow's glue everyone knows & loves. Just keepin' it cool. :eek:

 

YouTube - Laminar Flow Fan Duct Construction http://www.youtube.com/watch?v=SksAlUx_J1c

[freeztar]

I have started...er...picked back up construction of an experimental laminar flow fan duct.

 

Can you explain this in detail Turtle? The video didn't clarify it for me.

[Turtle]

Can you explain this in detail Turtle? The video didn't clarify it for me.

 

All the 'splainin is to follow of course, but it did occur to me that maybe I should have started a new thread in the Science Project section. Feel free to split this off if you think it better.

 

To summarize, imagine you have a lighted candle, and the fan as it comes. If you use the fan to blow out the candle, there will be a maximum distance between the 2 where the fan no longer blows out the flame but only wiggles it.

 

Now all else being equal, that is not speeding up the fan or using a different one etcetera, what can we do mechanically to increase the distance from which we can blow out the candle?

 

My hypothesis is that placing a duct packed with cylinders will achieve that aim, and by an impressive amount. The principle that accomplishes this is laminar flow, and rather than modifying an object moving through air, here we are modifying air to move through air, or as the title has it, we are going to lubricate the air itself.

 

While the glue is drying I'm considering if it's worth building a small wind tunnel? Off to check the glue and cut some more 4" sections of straws. ...........:eek:

[freeztar]

Uber-cool Turtle!

 

So are you just lining the inside edge of the cylinder, or are you planning on filling it in with more straws?

 

I'm still uncertain about how the laminar flow is occurring in your model. Is it just because the straws isolate the air flow and hence reduce drag? Or is it because the straws create a much higher pressure?

[Turtle]

Uber-cool Turtle!

 

So are you just lining the inside edge of the cylinder, or are you planning on filling it in with more straws?

 

I'm still uncertain about how the laminar flow is occurring in your model. Is it just because the straws isolate the air flow and hence reduce drag? Or is it because the straws create a much higher pressure?

 

The edge lining is just the first layer, and the entire cavity is ultimately filled yes. I decided to make a video showing the construction steps, as when it is done it may not be obvious how it is made.

 

I have conducted similar experiments on a smaller scale, and I do know this arrangement is how those jumping fountains produce a cohesive laminar flow stream with water. I don't want to hastily jump into an explanation of how/why it works before I have a proper understanding of it myself, but I know it does work and I want to demonstrate it while I explore some aspects of the effects that I am personally curious about. I am not aware of anyone else doing this, but I'd love to learn of it.

 

I have had to settle for certain conditions I would avoid if I was engineering this under an unlimited budget. For example, I would make the duct the same diameter as the fan and in my machine the coffee can is smaller and so I have some backpressure developed from the venturi effect at the constriction. I expect this effect, and the additional backpressure from the straws, to have a negligable effect on the laminar flow exiting the duct.

 

It would be nice to besides tests using first no duct, and then the laminar flow duct, to include an empty duct, but my construction methods have excluded that option. I note that with my small scale experiments, an empty duct adds little if any distance to the candle flame blow-out standard. The empty duct is afterall very much the same principal as is well measured and even in use with propulsive fans as we have already discussed here.

 

I can run on, but I'll stop here. Perhaps someone would like to calculate the ratio between the cross sectional area of the straws over that of the inter-spaces formed between them. (Hint: no real measurements are needed for this calculation; it is a close packing problem.;)) .......:hihi:

[Turtle]

Alrighty thens. While you work on that close-packing ratio solution (which may matter if we wish to calculate the cross section of active duct because many of the inter-spaces are closed off by glue), I have finished up the first ring of straws in the duct. While I have used the term 'straws', 'cylinders' gives a better geometric picture, and each is in fact a duct itself. We are building a duct of ducts. Quack, quack! :)

 

I did the control run this morning and will have the video presently. The open fan can blow out my test candle from ~ 7 1/2 feet away. I have the first row of straws in place, and I see now I can do a ducted blow run after each row. With this first row, it should be a close approximation to the empty duct.

 

Now that we have all our ducts in a row, it's time for lunch. Smoke 'em if ya got 'em. :rolleyes:

[UncleAl]

Kinetic Temperature, Thermal Energy

 

Mach 20 = 6806 m/sec. For air with average molecular weight = 29 daltons, Mach 20 gives 80,000 C (most probable speed) to 52,000 C (RMS speed) as the apparent relative temperature of the surrounding atmosphere. What difference does surface "lubrication" make when sitting in a plasma furnace?

[alexander]

ooh i wonder if i could make a prototype for this for a car, obviously paper straws are out, but i am wondering if and how much it would increase the amount of air that is pushed into the engine by streamlining it's motion.... perhaps this would be interesting with a turbo?

[Turtle]

Kinetic Temperature, Thermal Energy

 

Mach 20 = 6806 m/sec. For air with average molecular weight = 29 daltons, Mach 20 gives 80,000 C (most probable speed) to 52,000 C (RMS speed) as the apparent relative temperature of the surrounding atmosphere. What difference does surface "lubrication" make when sitting in a plasma furnace?

 

As soon as I get a plasma furnace, I will check that out. :rolleyes: In the mean time I'm guessing the answer is 'not so much'? *;)

 

ooh i wonder if i could make a prototype for this for a car, obviously paper straws are out, but i am wondering if and how much it would increase the amount of air that is pushed into the engine by streamlining it's motion.... perhaps this would be interesting with a turbo?

 

Your creativity is enjoying a major spike these last couple weeks I have observed. :) I'm thinking this is going to be interesting with a lot of subsonic air velocity things.

 

Here's the control experiment vid with the open fan. ;)

 

YouTube - Laminar Flow Experiment - Control Run http://www.youtube.com/watch?v=eA_4RDZDhx0

 

*Reading the link I gather that passing a plasma through my ductedy-duct would not produce a laminar outflow because a plasma's motion can't be properly desribed by point-particle means, but rather requires atomic parameters such as spin?

[alexander]

lol off to break my dad's tdi jetta....

 

lol i have always been creative, just that recently i have had some time and money to put into that.... doing some photography, lots a modifying things, making some music, etc, amongst other projects.... i am interested in this though, i have seen the laminar flow for water prototype on a show not too long ago (one of the original ones) and i was amazed at how nicely that looked, so i was thinking that with that, you could probably create a turbo-like pressure effect, granted you have a thicker pipe of filtered air coming into a laminar flow control thing, and then a coupler stepping down the tube size to the size of the normal air hose going into the intake manafold. I bet i could probably get a couple of lb of pressure out of the system without adding any moving parts to it, and i can almost guarantee that this would be way better then a "tornado". Also you can still create a tornado-like effect if you spiral the tubes a little bit, though i dont know if that would be needed considering the fact that you will have air pressure built up by the system anyways...

[Turtle]

lol off to break my dad's tdi jetta....

 

lol i have always been creative, just that recently i have had some time and money to put into that.... doing some photography, lots a modifying things, making some music, etc, amongst other projects.... i am interested in this though, i have seen the laminar flow for water prototype on a show not too long ago (one of the original ones) and i was amazed at how nicely that looked, so i was thinking that with that, you could probably create a turbo-like pressure effect, granted you have a thicker pipe of filtered air coming into a laminar flow control thing, and then a coupler stepping down the tube size to the size of the normal air hose going into the intake manafold. ...

 

Sounds like the same show that got me interested. I have done water versions like on the show, and the step down need only be a flat plate with a centered hole sized to fit your application. I plan to experiment with this by using interchangeable plates (coffee can lids with holes :lol:) situated in front of the outflow side of the duct.

 

Here's experiment run #2: blowing out the candle with the empty duct attached to the fan. As I earlier surmised, the result is worse than the control, that is I had to get closer. The maximum distance for blowout is ~5.5 feet, which is 27% closer. ........:eek:

 

YouTube - Laminar Flow Experiment - Empty Duct Run http://www.youtube.com/watch?v=SCkBpOp95hA

[alexander]

hmm... *ponders for a second*

 

perhaps i should contribute... smaller though, i should get a computer fan (use battery to power it), and then attach a soup can to that, fill it with straws (got plenty of those at work, thin ones too) and yeah see what it is going to do, then i can use more soup cans to make different shape step-down adapters, and its more of the size of a car intake duct...

 

sounds like a project :rolleyes: