- #1
user079622
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Does wing really fly in already downward moving air?
Video from 18:15 - 19:40
Video from 18:15 - 19:40
Does a wing fly in its own downwash?
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Discussion Overview
The discussion revolves around the concept of whether a wing flies in its own downwash, exploring the dynamics of airflow around wings in aerodynamics. Participants examine the implications of downwash and upwash in relation to wing performance, including comparisons to two-dimensional airfoils and the effects of wingtip vortices.
Discussion Character
- Debate/contested
- Technical explanation
- Conceptual clarification
Main Points Raised
- Some participants suggest that a wing produces both updraft and downdraft, indicating that it is not simply in downwash like a wing following another aircraft.
- Others argue that the airflow dynamics are complex, with upward movement of air ahead of the wing and downward movement behind it, leading to uncertainty about the overall flow pattern.
- A participant questions the validity of a video reference that claims air ahead of the wing is moving downward, asserting that they observe upward movement instead.
- There is a discussion about the differences between two-dimensional airfoils and three-dimensional wings, with some asserting that downwash effects are not applicable in two-dimensional cases.
- Some participants note that the flow is not uniform across the span of the wing, suggesting that there may be both upward and downward flows in different areas.
- One participant raises a question about the implications of downwash concepts for aircraft with winglets, suggesting that their performance contradicts a strict interpretation of downwash effects.
- A metaphor comparing aircraft flight to jogging in sand is introduced, emphasizing the deformation of the medium and the additional work required to maintain flight.
Areas of Agreement / Disagreement
Participants express differing views on the nature of airflow around wings, with no consensus reached on whether a wing flies in its own downwash. The discussion remains unresolved, with multiple competing perspectives presented.
Contextual Notes
Participants note the complexity of airflow dynamics, including the influence of aspect ratios and the limitations of two-dimensional representations in understanding three-dimensional wing effects. There is also mention of the need for more detailed flow field representations to clarify these dynamics.
- #2
FactChecker
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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.
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.
- #3
user079622
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What @boneh3ad tell about this?
- #4
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I don't understand the question.
- #5
user079622
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If wing fly in own downwash, that would mean air ahead of the wing already moving downward.boneh3ad said:
Author in my video tell that in 18:47
So I ask is this case in reality?
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- #6
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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?
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?
- #7
user079622
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Because I see upward movement of air ahead of wing...not downward..boneh3ad said:
- #8
russ_watters
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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 said:
- #9
user079622
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OK just reduce this upwash a little but and you get picture for wing.russ_watters said:
Or you want to say that air moves downward ahead of wing ?
- #10
DaveE
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russ_watters said:
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.user079622 said:
- #11
russ_watters
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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 said:
- #12
user079622
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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
- #13
FactChecker
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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.
- #14
user079622
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This is upwash ahead of wing for different aspect ratios.FactChecker said:
russ_watters said:
This CFD is made on wing , it show airfoil because show streamlines at one place at wing ..it show wing profile at that location
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- #15
Nik_2213
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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...
Given they fly better than without, there's an over-simplification some-where in OC's source...
- #16
Drakkith
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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.
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