How does a Whip Break the Sound Barrier? Behind the Scenes- Smarter Every Day

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The awesome German Paper:

University of Arizona paper:

History of Shock waves:

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April Jennifer Choi is a Mechanical Engineer and Professional Whip Artist from Peoria, IL. She has a Master's Degree in Computational Fluid Dynamics as well as several Guinness World Records in Whip Cracking. April is also a well known Fire Performer and you can check out what she does on Social Media through these links.
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Ambiance and musicy things by: Gordon McGladdery did the outro music the video.
The thought is it my efforts making videos will help educate the world as a whole, and one day generate enough revenue to pay for my kids college education. Until then if you appreciate what you've learned in this video and the effort that went in to it, please SHARE THE VIDEO!

If you REALLY liked it, feel free to pitch a few dollars Smarter Every Day by becoming a Patron.

Warm Regards,

Destin

[SumGuyLovesVideos]

I love the intense scrutiny and seeing the minds' "gear spinning" as y'all dig into the different perspectives and possibilities :D

[nxt]

These videos have seriously gone up several levels in terms of quality of content and engineering principles recently. I cant wait to see what is next!
P.S. as an acoustic engineer put your ear defenders on without the cap underneath (and possibly not upside down)
and as a safety sally, a water bottle isn't a replacement for protective googles.

[PierceArner]

Jeeze, this video and its companion on the main channel are some of the coolest things that I've seen in a _Long_ time! Fantastic work as always!!

[BazilRat]

This is the sound of a very complex physics paper being written.

[AprilJenniferChoi]

Destin, Thank you so much for making this video!

[youtooyoutoo]

13:56 ; Excellent positioning of the parabolic compression wave in the field of view.
Remember that it might help, but taper is not required. Forty years ago as a young engineering student, I wrote a research paper based on microphone recordings in an anechoic chamber for describing this structure for the formation of the wave-front. (My original hypothesis (like yours?) was that the shock wave would be perpendicular to the whip travel, during the change in tip direction.)
Cylindrical whip cross-section (constant diameter line) seems more dependent on the back-stroke to focus the kinetic energy into the tip. The shock wave requires both speed and a physical cross-section discontinuity (tip). Larger mass lowers the speed, and a small discontinuity seems sufficient for efficient transfer of energy from the whip to the air. I also noticed that the compression wave causes what looks like chaotic displacement of the tassel fibers within the wave crest (which might be critical?).
I am curious about the effect of the shape of the tassel on the efficiency of the shock wave formation; you only reported use of two tips: a 'standard' tassel and a ball (much too big for good transfer). However, more or fewer fibers, and the range of fiber length would seem to be parameters of the energy transfer.
I presume that the adoption of a tassel by the sport was that it lasted better than blunt or mono-filament. That might tell you something about the fiber strains and energy dynamics in the transfer process. The sport probably also chose the whip length for practical reasons like the 'depth of field' for target acquisition, against efficient compression wave generation (although a good sharp crack might also be a 'fun' factor).

[domainofscience]

You know how scientific papers are the highest standard where scientific results are published. In 2018 I find that old fashioned as there are so many richer ways of presenting the research process. There were times in my research where I could not replicate the experiment from papers alone because there was insufficient information to go on in the paper. It's be cool if scientific research could be published in video form as it is the richest data stream, but I guess we are stuck with the traditional paper format.

I know that is not what you are trying to do here, but I got a really good idea about your experimental setup that would be hard to communicate in a paper. Anyway, looking forward to see how it all pans out!

[Ratteler]

You "dropped" Prince Rupert. :-p

[hershycows]

What really impresses me about Destin is he doesn't seem to annoy anyone when he is filming all this stuff. That's some good people skills right there.

[ASoggySandal]

I love how much more apparent it becomes that air is a fluid when viewed in slow-mo through the schlieren

[maccrazy]

It's a pretty tranquil arm-movement for something at the end reaching the sound barrier. Amazing!

[joshmckinney]

I think it just clicked! You said something in the other video about the whip popper being "pulled" along after the shock wave. The way it works in my head is more like a rocket passing through Max Q: as the popper accelerates, it builds up pressure along the leading edge. The aerodynamic pressure builds and builds as it becomes transonic, but the pressure drops off once the popper is supersonic. This sudden drop in aerodynamic pressure coupled with the (more or less) constant acceleration of the rolling whip results in the acceleration of the popper building, plateauing and picking back up, which is what you noticed. That's so cool!!

[Erni]

I love your approach to this problem and the way you thought to collect several kinds of data and analyse all of it.

[fltmedic]

I am a AE and i could watch your channel all day keep up the great work my friend, i encourage my 12 year old daughter to watch your channel and she loves it, thank you.

[celtgunn]

Destin, I think that to fully appreciate the Smarter Every Day video about whip cracks people really should see this behind the scenes about it too.

Great job on this. I look forward to hearing about the paper y'all write up.

[GadgetReviewVideos]

Wow, brings back childhood memories. I was cracking a bull whip 30 years ago and I’m 43 now. It was a souvenir from a place called frontier town in Berlin Maryland. Even learned to pan for gold (fools gold that is) and had my mind spinning back then. It’s changed, but I spent hours at home in the back yard changing he length of the tip and sound of the whip learning it. To watch childhood theory’s and experiments get documented like this is amazing. I don’t even remember if I understood it was breaking the sound barrier when I was 13 years old.

[dbayboyds]

Just a quick thumbs up for April! Tech is awesome but how impressive is her skill at getting the whip to crack in such a small area time after time! I bet she was bodily tired afterwards.

[rrrosecarbinela]

This is not only great science... It's beautiful! Awesome research, and excellent video!

[jamminpsd]

Ok. That last slow mo shot. Just the audio was worth the watch of the behind the scenes vid. Not to mention the epic content! So glad you did this!!

[olekaarvaag]

One of the best BTS videos so far. Love to see the excitement, joy and good energy in the room when everybody is so stoked about learning and understanding.