false aerodynamics website

[annihilator]

I know many people on this forum use freely available information on the web to learn about aerodynamics. This is just my warning to the rest of you about a website I happened over tonight.

I'm an aerospace engineering graduate from Oklahoma State, and have had quite a lot of success in the field using all the techniques the gentleman at www.aeronautics.ws says are false.

Please do not take the things he says to be true, they are MISLEADING and JUST PLAIN WRONG.

[Flight Engineer]

I concur.

[nmasters]

But... but...but... He's an ex navy pilot and CFI. :confused: By his own admission Clifton Gene Gent is a rational, intelligent person with a genius IQ. Nowhere in his description of himself (http://www.aeronautics.ws/russell_cummings2.html) dose Clifton Gene Gent give any hint that he recognizes that pilot training does not lead to any kind engineering degree.

[Tim Green]

Well - some of you guys all state this guy's wrong - but you're not getting technical - you're just ranting at the guy. Care to get specific?

[nmasters]

Here ya go Tim
http://yarchive.net/air/lift.html

http://hyperphysics.phy-astr.gsu.edu/hbase/fluids/kutta.html

http://en.wikipedia.org/wiki/Kutta_condition

http://www.arvelgentry.com/origins_of_lift.htm

They explain it so much better than I could have

[BMatthews]

From the little I looked at he isn't totally off base with all his claims but instead chooses some things to champion and then tries to debunk and toss out the rest without taking the time to realize that a lot of it is linked.

I have to agree with him about the poor way that the Bernoulli theory works with airplane wings though. But that's pretty much known to one and all already.

[ciurpita]

i think he definetly didn't understand the purpose of the lift-bodies. i know the name is very misleading, but the lifting bodies research proved in the de-orbiting approach used by the space shuttle -- to be able to control a wing-less non-powered aircraft and land on a conventional runway (as opposed to a space capsule). i don't think the lifting bodies were even intended to be able to develop sufficient lift in order to maintain altitude.

[Brandano]

The original lifting body research was to maximize cargo area while minimizing structural weight. While promising it didn't turn out quite as well as expected, and that's why the shuttle has wings. No point in going the troublesome unproven route when there's a better proven one available, the space shuttle project had already enough risks to deal with.

[JetPlaneFlyer]

I have to agree with him about the poor way that the Bernoulli theory works with airplane wings though. But that's pretty much known to one and all already.

Whats wrong with Bernouli theory in regard to wings :confused:
I think sometimes people say 'Bernoulli does not work' when what they are really refering to is the false 'equal time of transit' theory. Because equal time of transit is rubbish these people then go on to make the illogical leap to conclude that Bernoulli does not apply to wings, or as the guy on this web site appears to be claiming that Bernoulli's principal is completely wrong.

[annihilator]

the bernoulli principle is true, its just that it only applies to streamlines and once flow seperates from the rear of the airfoil in a normal wing, the streamline does not follow the contour of the surface anymore.

He talks a lot about how camber does not increase lift, just pushes the front of the airfoil down..... camber does cause an increased nose down moment, but does also increase the zero lift angle of attack of any airfoil. In his "wind tunnel" test he tries to show that camber just makes an airfoil spin, and it does spin. Thats only because it is pinned at the 50% chord, we all know that the center of pressure is around the 25% chord for subsonic. The resulting moment created by the camber of the airfoil overpowers the moment created by lift and it begins to rotate nose down. If he started the test at a higher angle of attack instead, the lift moment would overpower the nose down and it would flop over backwards. Cm is reasonable constant for small angles and small % thicknesses.

I would keep going into more about unsteady aero and his "accelerating airfoils" etc... but I dont want to waste my breath. Just trust me, his website is quite wrong.

[Odysis]

I'm always concerned when a pilot tries to explain aerodynamics.

Engineers deal with dCl/dt
Pilots deal with "stick back, houses smaller"

Also, anyone who tries to discredit the "establishment", in any field, is asking for trouble. That's why professional journals are all about peer review.

[Brandano]

the Bernoulli principle applies also to a shape where a separation occurs, but in that case you should consider the wing and separation bubble as being a single item. Fundamentally, the Bernoulli principle works fine for that region of flow that is laminar, non turbulent. If someone says that the Bernoulli formulas does not work, ask them to explain carburettor icing.

[MarkusN]

I'm really getting fed up by all that "I can't wrap my mind about that complicated stuff so it must be wrong" stuff being thrown about in the field recently. Sure, many physical models that we have been force-fed have been grossly over-simplified. And trust teachers who haven't completely grasped the concepts they have to teach to add to the mess as well. But the pseudo-scientific Bernoulli-bashing that the web spurts eveywhere is really annoying.

Potential theory is great to describe many aerodynamic problems. One has to be aware of tis limitations, and usually you have to use some "tricks" to make the model conform to what you observe, but then it yields good results and makes problems accessible to calculation.

[Julez]

http://jef.raskincenter.org/published/coanda_effect.html

[Tim Green]

http://jef.raskincenter.org/published/coanda_effect.html

I've seen it before - a great analysis of lift. I like how he backed up his hypothesis with his own experiments. I've duplicated his airfoil/straw experiments - and got the same results. Finding that just having a faster airstream on the top isn't enough - the wind has to be moved in a downward direction, before lift takes place.

[kcaldwel]

If someone says that the Bernoulli formulas does not work, ask them to explain carburettor icing.

Carb icing is almost entirely due to the evaporation of the fuel. That is about the only thing he gets right on that web site.

How did you think it happened?

Kevin

[Brandano]

Carb icing is due to the temperature drop caused by the gas expanding within the carb venturi. It's a direct consequence of Bernoulli's gas dynamics laws. The flash point of most fuels is already low, if the evaporation alone was sufficient fuel would freeze on the surface whenever left in an open container. You can get carb icing weven without fuel flow, if there's moisture in the air.

[kcaldwel]

The pressure drop in most carbs is about 300 Pa. This gives a temperature drop of about 1C. While that will certainly cause icing under very particular conditions, the temperature drop caused by fuel evaporation is much larger, and can cause icing at 20C and high humidities.

Aircraft running on MoGas have to be much more careful with carb icing due to it's higher volatility, and increased rate of evaporation in the carb throat itself causing greater cooling.

Try pouring some gasoline on your hand and waving it around, or rubbing alcohol. The cooling rate is very high. The fluid sitting in a container has a very low evaporation rate. Try a swamp cooler if you want to see how a bit of water evaporating can cool a lot of air by many degrees. The venturi refrigerators use high pressure air at several atmospheres from a compressor to achieve their cooling effect.

Anyway, this is getting off topic, other than the site does use carb icing as another justification of his flawed theories.

Kevin

[Neil Stainton]

What about wing icing?

[kcaldwel]

Wing icing is generally impact accumulation with supercooled droplets. That can also occur in the up stream intact tract of an engine, but the droplets usually don't make it as far as the carb. Dangerous none-the-less.

You get ice build-up on all areas facing the air stream, not just the low pressure area on the top surface. I've had arm icing flying my hang glider!

Kevin