Does a wing fly in its own downwash?

[user079622]

Does wing really fly in already downward moving air?

Video from 18:15 - 19:40

 

[FactChecker]

I am not an expert in aerodynamics, but here is my two cents:
The wing is disturbing the horizontal air flow so that the air ahead of it is going up and the air behind it is going down. So it is "in" (as in producing) both an updraft and a downdraft that it is in the middle of. Because it is producing these effects, this should not be considered the same as a wing in the downwash of another airplane. Confusing that would be like confusing cause and effect.

 

[user079622]

What @boneh3ad tell about this?

 

[boneh3ad]

I don't understand the question.

 

[user079622]

I don't understand the question.

If wing fly in own downwash, that would mean air ahead of the wing already moving downward.
Author in my video tell that in 18:47
So I ask is this case in reality?

 

[boneh3ad]

I mean, his crudely-drawn hand sketch is not precise, if that's what you are asking.

But any object moving through a fluid medium is going to cause that fluid to deform around it. If it's subsonic, that influence on the medium extends upstream of the object. So, sure, some of that induced flow over a finite wing is downward, reducing lift.

Why are you asking me, though? Do you have reason to doubt Dr. Lippisch an his long career designing and building aircraft that actually fly?

 

[user079622]

So, sure, some of that induced flow over a finite wing is downward, reducing lift.

Why are you asking me, though?

Because I see upward movement of air ahead of wing...not downward..

 

[russ_watters]

Because I see upward movement of air ahead of wing...not downward..
View attachment 337150

That's an airfoil, not a wing. It's 2-dimensional. The downwash is a 3-D wing effect that doesn't occur in this 2-D case.

 

[user079622]

That's an airfoil, not a wing. It's 2-dimensional. The downwash is a 3-D wing effect that doesn't occur in this 2-D case.

OK just reduce this upwash a little but and you get picture for wing.
Or you want to say that air moves downward ahead of wing ?

 

[DaveE]

That's an airfoil, not a wing. It's 2-dimensional. The downwash is a 3-D wing effect that doesn't occur in this 2-D case.

OK just reduce this upwash a little but and you get picture for wing.
Or you want to say that air moves downward ahead of wing ?

The image in your OP shows wingtip vortices. Is that what you are asking about? In 2-D you don't have any beginning or end of your wing.

 

[russ_watters]

OK just reduce this upwash a little but and you get picture for wing.
Or you want to say that air moves downward ahead of wing ?

The flow isn't uniform across the span, so I'd say there's no general answer for the question. I suspect there is upwards flow in front of parts of the wing and downwards flow in front of other parts. But I don't think I've seen a 3D representation of the flow field.

 

[user079622]

By the way this CFD is made on wing , it show airfoil because show streamlines at one place at wing ..it show wing profile at that location

 

[FactChecker]

The net downward flow of the air is the cause of lift. But that is primarily aft of the wing. The wing is the cause of the downflow and does not have the same effect of a wing in a downflow from following another airplane. So not all downflows are the same.

 

[user079622]

The net downward flow of the air is the cause of lift. But that is primarily aft of the wing. The wing is the cause of the downflow and does not have the same effect of a wing in a downflow from following another airplane. So not all downflows are the same.

This is upwash ahead of wing for different aspect ratios.

That's an airfoil, not a wing.

This CFD is made on wing , it show airfoil because show streamlines at one place at wing ..it show wing profile at that location

 

[Nik_2213]

If 'downwash' concept was strictly true, wouldn't aircraft with winglets / tip vortex recovery devices be unable to fly ??

Given they fly better than without, there's an over-simplification some-where in OC's source...

 

[Drakkith]

What I got from the video is that an aircraft flying through the air is like a person jogging in sand. The air and the sand both deform when weight is applied and you have to perform extra work to account for this. For the aircraft, this may already be shown in the airflow diagrams provided, but I doubt that's something that can be 'eyeballed' from them.