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Lift force acting on a fly line

Moderator: Torsten

Torsten
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Re: Excellent FP on modeling

#301

Post by Torsten » Sat Jul 20, 2019 4:02 pm

Why not calling that thing Aerodynamic Lift Force (ALF) then?
alf_small.png
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Paul Arden
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Re: Excellent FP on modeling

#302

Post by Paul Arden » Sat Jul 20, 2019 4:46 pm

Blimey this is like Spinal Tap trying to agree if they played at a Jazz-blues festival or a Blues-jazz festival :D
It's an exploration; bring a flyrod.

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Walter
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Re: Excellent FP on modeling

#303

Post by Walter » Sat Jul 20, 2019 6:42 pm

gordonjudd wrote:
Sat Jul 20, 2019 3:25 pm
You’ll find squillions of results for one and only one for the other.
Walter,
If that is the case then explain to me how "lift induced drag" applies to the wind gauge experiment?

I don't even see how it applies to a dropped piece of line if that is one of the squillions of results you are talking about.

Gordy
Gordy my sense is that if you are relying on the term “drag induced lift” to do your research then you only have one very short paper to guide you and it won’t help much. You need to properly understand terms like lift, drag, thrust, angle of attack, terminal velocity and lift induced drag in order to research and use the incredibly rich source of information that the internet has available with respect to aerodynamics. I provided a few references earlier that might help. NASA also has some great information.

The truth is out there.
"There can be only one." - The Highlander. :pirate:

PS. I have a flying tank. Your argument is irrelevant.

PSS. How to generate a climbing loop through control of the casting stroke is left as a (considerable) exercise to the reader.

Magnus
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Re: Excellent FP on modeling

#304

Post by Magnus » Sun Jul 21, 2019 12:34 am

Edit Torsten: quote from the modelling thread, post #43:
@all
My intention of the lift thread was to investigate the influence of the lift-induced drag (this is the standard aerodynamics term) and not lift or rising in general. We can call it DOG - although this a bit funny abbreviation. My fault was that I've not clearly enough defined the scope of this topic and the topic title was also misleading. I'm not sure yet if I'll open up a new one with a summary and roadmap or if I'll continue the old one - have to think about this, tell me if you have some preferences.
https://en.wikipedia.org/wiki/Lift-induced_drag
FFS

Hi Torsten
If that meaning of Lift-induced drag is to be believed I don't see the equivalent in your into to the lift thread. Not sure I see the relevance of the concept to fly line.

Magnus
"Actually I can't because you are right! " Paul Arden 8/6/2019

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Merlin
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Re: Excellent FP on modeling

#305

Post by Merlin » Sun Jul 21, 2019 1:05 am

Gordy

Drag induced lift is just lift, the words « drag induced » are redundant.

Lift induced drag is a specific kind of drag associated to lift, due to the evolution of the flow. It is not applicable to a fly line IMHO.

Merlin
Fly rods are like women, they won't play if they're maltreated
Charles Ritz, A Flyfisher's Life

Torsten
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Re: Excellent FP on modeling

#306

Post by Torsten » Sun Jul 21, 2019 12:19 pm

Hi Magnus,
If that meaning of Lift-induced drag is to be believed I don't see the equivalent in your into to the lift thread. Not sure I see the relevance of the concept to fly line.
this is true, it has for airfoils a different meaning (e.g. drag is the horizontal force opposed flight direction). I think that was the reason why I've used only lift force in the other thread, like in the linked paper. What we mean is a upward directed force as a result of aerodynamics, the ALF (Aerodynamic Lift Force(s)) or DOG (Drag opposed gravity) :)

Magnus
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Re: Excellent FP on modeling

#307

Post by Magnus » Sun Jul 21, 2019 12:35 pm

What we mean is a upward directed force as a result of aerodynamics, the ALF (Aerodynamic Lift Force(s)) or DOG (Drag opposed gravity) :)
Sorry Torsten, am I missing your meaning? Am I right is saying neither of those (Aerodynamic lift or drag as the body falls) is lift-induced drag - and in fact the term lift-induced drag (LID ?) has yet to find any use whatsoever in looking at fly line 'flight'?

Magnus

(BTW Not enjoying all the acronyms)
"Actually I can't because you are right! " Paul Arden 8/6/2019

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gordonjudd
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Re: Excellent FP on modeling

#308

Post by gordonjudd » Sun Jul 21, 2019 1:21 pm

It is not applicable to a fly line IMHO.
Merlin,
I see it the same way although there is certainly a drag force in the -x direction that is associated with the lift force in the +y direction. As the tilt angle of the line increases the +y lift to -x force ratio will decrease. There is no free lunch.

You cannot change the momentum of the air with a moving inclined section of line without producing forces in both the x and y directions.

The lift that results from a simple momentum change is different than the multitude of effects that produce lift due to the flow of air around a curved airfoil such as a wing in an airplane.
in fact the term lift-induced drag (LID ?) has yet to find any use whatsoever in looking at fly line 'flight'?
Magnus, I agree with that assessment. I don't think the lift-induced drag concept for an airfoil has any relevance to a moving piece of fly line.
NASA also has some great information.
Agreed. You just have to search for videos that apply to a fly line, not an airfoil.

This video from NASA is much more relevant to demonstrating the lift that comes from the air's momentum change that happens when in inclined section of fly line moves through the air.
Image

Gordy

Torsten
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Re: Excellent FP on modeling

#309

Post by Torsten » Sun Jul 21, 2019 1:21 pm

Yes, this can be quite confusing, I'd rather say it for the fly line the other way around - drag induced lift - but that's not a known term. See also Daniels post #53. So just lift force is more general, perhaps we should think more about the overall influence of aerodynamics on the fly line - because we have not just a component in y-direction, but also in x-direction.

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gordonjudd
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Re: Excellent FP on modeling

#310

Post by gordonjudd » Sun Jul 21, 2019 1:32 pm

drag induced lift - but that's not a known term.
Torsten,
"Lift induced by a y momentum change of air" is probably a more accurate description, but it is a mouthful to say.

Why does the center of mass of a length of line rise when it is exposed to an air stream? I see the source as being form drag. So from a cause and effect standpoint I see the cause as form drag and the effect as the lift of the line. Thus drag-induced lift does not seem to be too far off the mark

Gordy

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