This is a response to @Veritasium 's recent video: Risking My Life To Settle A Physics Debate
   • Risking My Life To Settle A Physics D...  
I show all the extra steps that I used to understand what on Earth is going on here! Mostly I relate it to aerodynamics and especially the blade element method that is commonly used to analyse wind turbines. And I also show why it doesn't violate the laws of thermodynamics.

It is the subject of a $10,000 bet as tweeted here:   / 1403130178197278720  

I need to give the HUGEST thank you to Rick Cavallaro the designer of the Blackbird vehicle, for giving me extra design information and helping clear up all the physics and engineering involved until I understood it.

If you would like to help develop the Engineering with Rosie channel, you could consider joining the Patreon community, where there is a chat community about topics covered in the videos and suggestions for future videos and production quality improvements.   / engineeringwithrosie  

Bookmarks:
00:00 Intro
00:29 Bet between Derek Muller and Alexander Kusenko
02:14 Description of how the Blackbird cart works
02:58 Analogy: like a cyclist pushing off a car to go faster than the car
03:56 A perpetual motion machine? The wheels turn the propeller, but they don't power it
04:51 This clearly violates the laws of thermodynamics!
05:38 Energy balance with some simple numbers
07:22 How it gets moving from stationary
07:56 It's not a wind turbine
08:45 Why the propeller's thrust is larger than a push from the tailwind can be
09:32 Aerodynamic concepts: lift, drag, angle of attack, relative wind speed
10:29 Aerodynamics of a propeller
11:00 Blade element model of the Blackbird propeller
12:27 Aerodynamics (vectors analysis) of the Blackbird propeller at record conditions (2.8 times wind speed)
13:26 Propeller aerodynamics at faster than record conditions
14:01 Propeller aerodynamics at wind speed (zero relative wind speed)
14:43 Slower than wind speed
14:56 Link to more analogies from Rick Cavallaro the Great
16:29 Bonus analogy: a propeller is a kind of screw

Extra resources to understand the concepts in more depth:
Designer Rick Cavallaro's long speech with many analogies:    • DDWFTTW Talk 2017-01-18  
Putting numbers on iceboat performance (analysis and GPS data that shows boats moving many multiples of wind speed) https://www.nalsa.org/Articles/Cetus/...
Sailing yacht design for maximum speed: http://static1.1.sqspcdn.com/static/f...
Eyytee's animation showing how sail vehicles are able to outrun the wind, that pushes them (achieve a downwind velocity-made-good greater than true wind speed). As an analogy a wedge squeezed between two oblique edges is shown.
   • DOWNWIND VMG GREATER THAN WINDSPEED (...  
Performance of propellers lecture notes from MIT course "Thermodynamics and Propulsion"
by Prof. Z. S. Spakovszky (includes blade element method): https://web.mit.edu/16.unified/www/FA...
NASA propeller thrust page: https://www.grc.nasa.gov/www/Wright/a...
Aerodynamics for students Blade Element Theory for Propellers (nice simple version that I used):
http://www.aerodynamics4students.com/...

A written version of the same material is here:
https://rosemary-barnes.medium.com/do...

Image and footage credits:
Risking My Life
Defender By Donan.raven - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index...
Ice boat By HopsonRoad - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index...
Ice boat pdf https://www.nalsa.org/Articles/Cetus/...
Ice boat By Raul Kern - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index...
Ice boat By Pataki Attila István - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index...
Downwind faster than the wind wedge animation    • DOWNWIND VMG GREATER THAN WINDSPEED (...  
Screw animation By ja:User:＋－- Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index...
The aeroplane on a treadmill image from xkcd
https://blog.xkcd.com/2008/09/09/the-...

#engineering #science #stem

Thanks for watching the video Downwind Faster Than the Wind by Veritasium: How Does it Work?