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Basic aero questions


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#1 Bikr7549

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Posted 18 October 2020 - 18:20

Hi,

Regarding induced drag, I understand where it comes from-the horizontal element of the resultant lifting force due to the rear facing lift vector.

 

But what is this 'horizontal' element in relation to? The ground, mean chord line or the direction of travel?

 

What is the correct term for this plane?

 

Is it possible to have a 3D lifting aero shape (not something symmetrical) in which all the lift is perpendicular to the 'horizontal' plane, so that there is no induced drag?

 

Thank you,

Bob



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#2 Bloggsworth

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Posted 18 October 2020 - 19:28

No.



#3 DogEarred

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Posted 18 October 2020 - 19:41

Helium balloon in air?...

#4 PayasYouRace

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Posted 18 October 2020 - 21:50

Hi,

Regarding induced drag, I understand where it comes from-the horizontal element of the resultant lifting force due to the rear facing lift vector.

 

But what is this 'horizontal' element in relation to? The ground, mean chord line or the direction of travel?

 

What is the correct term for this plane?

 

Is it possible to have a 3D lifting aero shape (not something symmetrical) in which all the lift is perpendicular to the 'horizontal' plane, so that there is no induced drag?

 

Thank you,

Bob

 

The induced drag is measured in the free stream direction, just as the lift is measured in the direction normal (perpendicular) to the free stream direction. In reality, what you're getting is a single force, angled backwards due to the 3D nature of the shape producing it.

 

The difference in angle between the free stream direction and the mean chord line is the angle of attack.

 

No, it isn't possible to produce lift without induced drag. On a fundamental level, you can't produce lift without changing the direction of the airflow, and the change in direction means you will be creating some drag.



#5 Bikr7549

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Posted 18 October 2020 - 22:10

Helium balloon in air?...

 

Probably not as that is a buoyancy thing rather than an airfoil, but a good try.

 

Thanks PAYR, that is exactly what I was looking for.  



#6 DogEarred

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Posted 19 October 2020 - 11:16

The 'balloon' comment was meant to be flippant but thinking about it, once the balloon starts rising, it becomes aerodynamic.

 

The air will pass the top (& bottom) point & will be forced horizontally at that point, in radial directions. The resolution of those forces will be zero. So you could say it has zero drag horizontally.

 

As the air passes further around the balloon towards its 'equator', the forces tend more to the vertical & there there are components of vertical & horizontal force (drag) but again the horizontal components, resolve to zero.

 

 

Personally speaking, I think there is more reward to be had by grabbing a needle & bursting the damned thing...



#7 Charles E Taylor

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Posted 19 October 2020 - 14:47

Hi

 

 

Aerodynamic References.

 

 

 

Not the lightest reading material, but you might find these references worth every penny.

 

 http://200.17.228.88...fia/Hoerner.pdf       Download and save the pdf file.

 

 

http://www.sfte.org/...17-addendum.pdf

 

 

The more you look the more you see.

 

 

 

 

Take Care.

 

 

 

 

 

Charlie.

 

 

 

 



#8 Greg Locock

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Posted 19 October 2020 - 22:06

I disapprove of piracy. Thanks.



#9 desmo

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Posted 20 October 2020 - 14:58

The 1st piece was published in 1965, the second link is to the official publisher's website. I believe in copyright too, but not to a crazy extreme.



#10 Greg Locock

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Posted 20 October 2020 - 21:31

Yeah, it is one of those horrible slippery slope dilemmas. Would I ever buy a new copy of Hoerner? Almost certainly not. So they haven't lost a sale. But... should the worker be denied the fruits of his labor?



#11 desmo

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Posted 21 October 2020 - 14:04

Well Hoerner died in 1971, so that ship has probably sailed now 50 years later.



#12 Greg Locock

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Posted 21 October 2020 - 20:18

I suppose i could burn the money.



#13 Allan Lupton

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Posted 21 October 2020 - 21:59

Well Hoerner died in 1971, so that ship has probably sailed now 50 years later.

UK copyright lasts 70 years after the author's death.

 

We had a copy of Hoerner at work (British Aerospace, Civil Aircraft Division) in the 1980s, and quite helpful it was too, even though it was many years after he wrote it.
 



#14 Greg Locock

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Posted 22 October 2020 - 02:23

This solar car was designed using Hoerner. We tested a few aspects of it using a 1/5 scale model on an 8x4 on the roof of a car.

 

https://www.amazon.c...a/dp/B07J5GR42L

 

The Evolution was designed using CFD by an ex F1 aero guy

 

http://new.aurorasolarcar.com/Cars



#15 Squeed

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Posted 25 October 2020 - 00:34

I have a question for the tech heads here:

Given the dirty-air-downforce issue with the current cars, would a blown diffuser manufacture the right kind of downforce to reduce the problem? 

If so, why hasn't it been discussed by the teams in the last few years?



#16 pierrre

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Posted Yesterday, 08:40

an exercise on possibilities what can be done with the front wing

 



#17 Bikr7549

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Posted Yesterday, 21:44

Will have to watch this a few more times, but thanks pierre. His youtube site has a few more interesting videos as well as this one.