Teardrop aerodynamics... in reverse!

[Frank Lee]

Keep scrolling up.

[winkosmosis]

A cone for a nose on a rocket sucks because it doesn't transition smoothly to the sides. And like I said, a sharp point is bad if airflow is approaching at an angle. That's why the NACA airfoil has a rounded front-- a wing has to be at an angle to airflow in order to generate lift.


Wikipedia:Reference desk/Archives/Science/2007 March 7 - Wikipedia, the free encyclopedia

One critical concept involving pointy-fronts on non-supersonic aircraft: if the nose is pointy, and if it hits the air at an angle, then there will be flow-separation on one side and sideways-directed frictional forces which lead to tumbling. Or if a wing has a sharp leading edge, and it hits the air with a positive attack-angle, then there will be major flow-separation above the wing, and major turbulent friction. It's called a "stall." Sharp leading edges cause the air-flow to peel loose from the object's sides. To avoid this situation, eliminate the sharp front parts and make them smoothly rounded. Pointy parts are only good for supersonic objects, and for objects having guide-fins which prevent it from tilting with respect to oncoming air. --Wjbeaty 03:30, 8 March 2007 (UTC)

[Frank Lee]

Great! I read your quoted Wiki and it says...

Pointy parts are only good for supersonic objects, and for objects having guide-fins which prevent it from tilting with respect to oncoming air.

You're welcome.

[hypermiler01]

Originally Posted by Frank Lee

and the air prefers the acceleration profile it provides over that of a straight walled conical nose section

And now tell us what the air prefers compared to a convex walled curved point.



The only valid comparison in this argument is the cD of a round nosed car compared to the exact same car with a pointy nose fitted to it.

Can you refute my claim of lowered air pressure?

[winkosmosis]

Originally Posted by Frank Lee

Great! I read your quoted Wiki and it says...



You're welcome.

I've been saying that for this whole thread. The reason for roundness is resistance to non parallel airflow.

That would be why the Jumbo jet doesn't end in a needlepoint, yet the overall profile is rounded like a parabola, not a dome... Because like hypermiler01 is saying, the angle of the surface affects drag.

[hypermiler01]

Originally Posted by Frank Lee

Because further pointiness is pointless for it!

So you admit that there is a point to the great deal of pointyness which it has, rather than looking like a flying ice cream cone?

[Frank Lee]

Originally Posted by hypermiler01

And now tell us what the air prefers compared to a convex walled curved point.

"What the air prefers"? Depends on what object we are talking about. Go slower than bullets and the leading surface need not be as pointy.

The only valid comparison in this argument is the cD of a round nosed car compared to the exact same car with a pointy nose fitted to it.

What is better than the Schlor car? Why is no pointy nose fitted? They weren't worried about styling or manufacturing constraints either.

Can you refute my claim of lowered air pressure?

Yes. Grab a book on aerodynamics and look at the many, many examples of aero shapes.

Perhaps some definition is in order? Such as what should be called blunt and what should be called pointy? http://ecomodder.com/forum/showthrea...ar-6982-4.html

Are we having a symantic problem with what is blunt and what is pointy?

Every pic except the Corcorde in my above post I consider blunt.

[hypermiler01]

Look how the airflow is being affected at least 2 feet in front of the car.
That is because the car is pushing a high pressure front ahead of it.

As for what's blunt and pointy, teardrop(hemisphere)=blunt, almost everything else in this thread=pointy.

I would place bets that the doodle bug thing would do even better than 0.13 with a lower stagnation point.

[Frank Lee]

Originally Posted by hypermiler01

As for what's blunt and pointy, teardrop(hemisphere)=blunt, almost everything else in this thread=pointy.

I would place bets that the doodle bug thing would do even better than 0.13 with a lower stagnation point.

Ah, there's 90% of our problem right there.

I would like a way to take that bet and confirm it.

[shovel]

maybe the area of higher pressure maintained at the front of a moving object becomes an invisible, self-directing point to oncoming air.