Is the cast itself a transverse wave?

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Is the cast itself a transverse wave?

Post Number:#191  Postby VGB » Wed Jan 24, 2018 7:37 pm

gordonjudd wrote:Vince,
As noted back in post 15:
An attempt to define the necessary and sufficient characteristics that qualify a phenomenon as a wave results in a blurred line.


In the case of kinetic waves, i.e.,
In gravity and pressure driven fluid dynamical and geophysical mass flows such as ocean waves, avalanches, debris flows, mud flows, flash floods, etc


Considerable matter may be transported in the wave flow.

Gordy


Gordy

As noted in the title, the thread is about transverse waves, not kinetic waves. We can blur the lines even further if we include shapes that look like waves when you squint and include phenomena that aren’t usually a part of fly casting such as avalanches and flushing the u bend.

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Is the cast itself a transverse wave?

Post Number:#192  Postby anjill » Thu Jan 25, 2018 8:26 am

Hi Gordy,

I really liked your demonstration of using the second bending mode of the rod to produce tighter transverse waves with less effort.

What camera or phone are you using to take your high speed videos?
Gordy


Twice as many transverse waves - superimposed on a transverse wave (or part thereof)? :D

Those clips were from a Casio Exelim FH20 at 240fps. Nowadays I usually just use an iPhone 7 at 120fps.

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Tony.
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Is the cast itself a transverse wave?

Post Number:#193  Postby gordonjudd » Thu Jan 25, 2018 3:12 pm

Twice as many transverse waves

Tony,

I don't know if you measured the tip frequency in your videos, but the frequency of the 2nd mode in a tapered rod is about 3.3 times the fundamental frequency. Thus if you are interested in producing more ripples in your "Zorro" cast, exciting the 2nd mode in the tip vibrations is a very clever way to do it.

I was not creative enough to think of it.

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Is the cast itself a transverse wave?

Post Number:#194  Postby gordonjudd » Thu Jan 25, 2018 3:53 pm

As noted in the title, the thread is about transverse waves, not kinetic waves.

Vince,
I would disagree.

This topic is about "is the cast itself a transfer wave?". In the true Sexyloops tradition of a thread never staying on topic and taking 20 pages of discussion, the short answer is no, the loop wave results in points in the medium traveling in same direction as the propagation direction of the loop and therefore is not a transverse wave.

So if it is not a transverse wave, how would researchers in wave mechanics characterize it?

There is probably no agreement on what that answer might be, but in this paper on The Propagation of Waves in a Cracking Whip Taft says:

When a whip is cracked, the user moves his or her arm back and forth, which
imparts energy on one end of the whip. This back and forth motion of the experimenter’s
arm creates a kinetic wave in the material. This wave propagates through the whip and
by the time it reaches the tip of the whip, that tip is moving at supersonic speeds.


Here is the shape of the wave he analyzed in his paper. You will note that it looks more like a fly casting loop wave rather than the tear shaped whip wave that Dr. McMillen studied in his thesis.
Image

Thus if someone who is an expert in wave mechanics call that propagating loop shape a kinetic wave, I am more than happy to accept that the loop wave we produce in casting can rightly be considered to be an example of a kinetic wave.

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Is the cast itself a transverse wave?

Post Number:#195  Postby VGB » Thu Jan 25, 2018 7:55 pm

Gordy

You may disagree but the transverse wave discussion was still continuing yesterday. However, I do agree the answer is no

There is probably no agreement on what that answer might be, but in this paper on The Propagation of Waves in a Cracking Whip Taft says:

When a whip is cracked, the user moves his or her arm back and forth, which
imparts energy on one end of the whip. This back and forth motion of the experimenter’s
arm creates a kinetic wave in the material. This wave propagates through the whip and
by the time it reaches the tip of the whip, that tip is moving at supersonic speeds.


Thus if someone who is an expert in wave mechanics call that propagating loop shape a kinetic wave, I am more than happy to accept that the loop wave we produce in casting can rightly be considered to be an example of a kinetic wave.


Thank you for sharing that paper,it looks very interesting. What common physics definition of kinetic wave are you using that binds whips, chains, string, avalanches, debris flows etc I would like to understand the shared characteristics, presumably this is not captured in the wave equation?

Here is the shape of the wave he analyzed in his paper. You will note that it looks more like a fly casting loop wave rather than the tear shaped whip wave that Dr. McMillen studied in his thesis.


It may look like a fly cast but it does involve a pulley mechanism which does change the dynamics somewhat.

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Is the cast itself a transverse wave?

Post Number:#196  Postby gordonjudd » Thu Jan 25, 2018 10:01 pm

It may look like a fly cast but it does involve a pulley mechanism which does change the dynamics somewhat.

Vince,
What do you mean by pulley mechanism?

I think he pulled the string around a smooth bar, much the same as I did with my coffee cup haul experiments to produce a loop wave in a fly line.

There is a difference in the way the initial loop shape is produced, but I don't see any difference in the dynamics constraining the way his u-shaped whip wave or the u-shaped fly wave would propagate.

Maybe you could elaborate on what you think is different about the dynamics.

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Is the cast itself a transverse wave?

Post Number:#197  Postby VGB » Thu Jan 25, 2018 10:06 pm

gordonjudd wrote:
It may look like a fly cast but it does involve a pulley mechanism which does change the dynamics somewhat.

Vince,
What do you mean by pulley mechanism?

I think he pulled the string around a smooth bar, much the same as I did with my coffee cup haul experiments to produce a loop wave in a fly line.

There is a difference in the way the initial loop shape is produced, but I don't see any difference in the dynamics constraining the way his u-shaped whip wave or the u-shaped fly wave would propagate.


Gordy

You have added another object into the system, we have no pulley, bar or coffee cup in the fly cast?

I’m looking forward to an answer to my question on what defines a kinetic wave.

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Is the cast itself a transverse wave?

Post Number:#198  Postby Paul Arden » Fri Jan 26, 2018 12:13 am

Interesting I had a read of that paper too recently. I figured bill whips would be the closest thing to flycasting that would have been studied. I had a go with a bull whip last time in Tasmania. While I can crack a flyline very easily (with pull back) I find the whip to be quite challenging (not to mention dangerous!).

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Is the cast itself a transverse wave?

Post Number:#199  Postby anjill » Fri Jan 26, 2018 3:18 am

Hi Gordy,

the frequency of the 2nd mode in a tapered rod is about 3.3 times the fundamental frequency.


Thanks for that pearl. I had never thought about the effect of the taper.

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Is the cast itself a transverse wave?

Post Number:#200  Postby Mac Brown » Sun Feb 04, 2018 4:17 pm

I think it would depend on who is the caster for a specific cast! The transverse wave has to have perpendicular right angled waves propagating down the line. So with really good fly casters that match power application and have excellent tracking, I doubt there is much of a right-angled component introduced into the morphing loop.

A high percentage of the masses tend to rotate the reel outward coming into the stop on the back casts. These loops have introduced a transverse wave into their back cast. This no doubts effects the accuracy of the forward delivery. I just finished a blog post on the subject since it is so prevalent for the masses.
https://macbrownflyfish.com/understandi ... -accuracy/

Great question and as Gordy's study group used to always say, "it depends".... :yeahhh: :yeahhh:
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