Physics - Vortex Shedding (Bobby Shew)

[Steve A]

A question for our resident physics experts - Bobby Shew talks about "vortex shedding" influencing pitch while playing, which he describes as being something that results from aiming the air at different points of reflection within the mouthpiece cup, which in turn increases or decreases the effective volume of the mouthpiece cup.

With no offence intended to Bobby Shew, who I know is a sensational player and teacher, I'm curious about this, since I've never seen anyone else describe this effect in these terms. In the opinion of people with physics training - is this a real and measurable phenomena, or is it an example of something that he finds helps, but where the scientific explanations don't match the outcomes?

https://youtu.be/6B0BftAOpwA?si=t4EdCkT-B1tmn7oG&t=5882

He specifically talks about the vortex shedding part and has a diagram to explain it at 1:39:20 into the video.

Thanks!

[JayKosta]

Aiming the air stream is done by changes to the lip positioning - alignment, tensions, jaw, etc. - those lip aperture changes, and the air flow changes (the 'quality air') that are necessary to accommodate the lip changes is how pitch and sound is adjusted.

There's no need for pseudo-science about 'vortex shedding'.
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Trumpet teaching is usually done with words and demonstration.
Learning to play trumpet is usually done by experimentation and practice.
If the teaching is good, it will lead to good experimentation.

[ConMoto9]

The way it feels VS. What’s really happening.

Absolutely no disrespect to the great Bobby Shew.
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ConMoto9

[Jazz Fan]

It might be true but it strikes me as pointless to think about something like this while playing. Did Doc, Maynard, Maurice Andre etc. concern themselves with it?

[JayKosta]

[Steve A]

So, another try - does anyone who knows enough about the physics to be able to answer care to share an opinion?

[kalijah]

A mental concept that encourages manipulating the aperture.

No truth to that in a "physics" sense.

Also, very much the case with the typical "air-speed" physics explanation to attempt to justify the tongue arch as a utility for ascending partials. The physical action does help but the popular "physics" explanations are simply false.

[Steve A]

Thanks kalijah - I appreciate your input. I've heard others describe the benefits they say result from a similar motion with a different explanation. I've also heard the suggestion that the playing experience (changing partials) Mr. Shew is describing is the result of changing the angle of reflection to points closer to or further away from the throat of the mouthpiece. Any thoughts about that?

[kalijah]

Angle of reflection? What "reflection"?
Air need only to enter the cup to add pressure to the standing wave. Angle is irrelevant.

[ConMoto9]

https://youtu.be/NpXC21yHbPU?si=hKlhxnLWzJmEDlXn

The great Bobby Shew.

Pretty wonderful!
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ConMoto9

[etc-etc]

Vortex-induced vibration has been often discussed in context of flutes and organs, but recently, also brass instruments:

https://vbn.aau.dk/ws/files/335384955/SMCCIM_2020_paper_63.pdf

[swthiel]

A response that will probably satisfy nobody ...

... but first a preliminary comment: what we're talking about here is a proposed explanation of why a technique works, and not a debate about whether or not it works. That said ...

Yes, you can get vortex shedding when a fluid flows through an aperture. As best I can tell from a quick literature search is that the flow characteristics are determined by the upstream conditions, the geometry of the aperture, and the acoustic impedances of the the aperture and the cavity receiving the flow. Most of the work I could find focused on burner design, with a few references for organ pipes, flutes, and clarinets. In burners, the aperture is rigid, unlike the aperture when we play trumpet.

I don't know that the direction of the fluid stream into the receiving cavity affects the acoustic impedance or the resonant frequency. If anyone here has a link to some published work on this aspect of the question, please share it. (Fluid dynamics isn't my specialty, but I can make my way through a paper about it.) If one of you would be willing to pony up the cash to support a grad student to do the computational fluid dynamics modeling, send me a PM -- I usually have some MS-level chemical engineering students looking for projects and this would make an interesting thesis topic, even if only computational.

[I've only had time to take a quick look at the paper etc-etc linked to, but it incorporated vortex-induced vibration into a model for the behavior of the lip reed. If there's detailed consideration of the geometry downstream of the aperture, I missed it when I skimmed the paper. Still interesting work.]

Unsurprisingly, I find myself in substantial agreement with kalijah -- I don't see technical support for the theory, but if it helps you do the things you need to do to play the way you want to play, go for it! I'd be the last person in the work to tell Bobby Shew how to play the trumpet!
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Steve Thiel

[ConMoto9]

Thank you, Dr. Thiel!

Really informative, most appreciated.
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ConMoto9

[JayKosta]

[Song_and_Wind]

[ConMoto9]

“ Due to how human beings are set up neurologically and physiologically, a player (1) NEVER knows what they are doing as they play in terms of all the various changes that occur in the body and (2) doesn't need to know a thing about it in order to play well. So, when someone comes up with a concept like "vortex shredding," they might as well work space aliens and Spock into the story as some sort of causative elements.”

Agree 100%.🎺

Although it’s interesting to ponder, it has very little to do with the art form.
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ConMoto9

[JayKosta]

[Steve A]

I wonder if we'll ever have a thread where someone asks a question specifically about something involving playing physics, asking for input from people with knowledge about that subject, and they don't get a bunch of people saying "too much thinking! You don't need this!"?

[Steve A]

[JayKosta]