Explained: Converging-Diverging Nozzle

Why do rocket engines look the way they do? In this video, I'll be explaining what a converging-diverging (CD) nozzle is, and how the flow changes as it passes through it.

See the Relevant Videos section below for some more in-depth videos on each of the flow states, including examples!

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===== NOTES =====
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► At 11:28, I say "so far, we have subsonic flow throughout the nozzle for all these cases." I meant to say that we have isentropic flow throughout the nozzle for all these cases.

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===== RELEVANT VIDEOS =====
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Pressure Ratio Delineations

Normal Shock in the Nozzle Calculations

Overexpanded Flow Calculations
Coming soon!

Underexpanded Flow Calculations
Coming soon!

Area-Mach Number Relation

Sonic State (Critical, Star)

Normal Shock Relations

Isentropic Relations

Stagnation Relations

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===== RELEVANT BLOG POST =====
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===== REFERENCES =====
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► Notes by Matt MacLean
► Modern Compressible Flow, Anderson
► Elements of Gasdynamics, Liepmann and Roshko
► Gas Dynamics, Zucrow and Hoffman

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===== THUMBNAIL IMAGE =====
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By NASA (NIX #: MSFC-0201422. [1], Alt. URL.) [Public domain], via Wikimedia Commons

[adhithasimhanraghavan]

I've never seen a person explaining the delaval nozzle this far. Genius man!

[thebeliever]

It's been 6 years & I am still watching this after reading it for 16 hours without understanding.
Thanks Josh

[philipligthart]

The first YouTube video that I don't have to play at 1.5 speed. Great work man

[tomwalker]

I wish this channel existed when I was studying engineering

[chess]

Was uploaded 5 yr ago! Still helping people out, beauty of internet.
The whole explanation was clear and you made it so simple, thank you teach.

[nanodynamics]

The way you organise the tutorial and the board is so fascinating
Thanks alot

[abhishalsharma]

I couldn't get Science subject due to no vaccancy. But I've always been enthusiastic for Science. And Rocket Science is something that I wanted to study for a long time and eventually I got u as a Fantastic teacher of Rocket Science

[Fran]

Hey Josh, very nice video!


I am doing my masters in Mechanical Engineering, and I've been struggling with the course of turbomachinery, since I did not have a very solid base in aerodynamics. However, following your channel I've been able to understand many things, and has allowed me to pass the course recently. Just wanted to thank you for your altruism in sharing your knowledge with us, and encourage you to never give up on that, it is highly appreciated.


Cheers man!

[ggBrUSA]

Josh, thanks again, you way of doing this is way better than my grad lectures...

[clarkbailey]

GOLD! I’ve struck GOLD! Thanks for the awesome video. Will certainly watch more.

[MegaTaizu]

by far the best theoretical explanation of CD nozzles. Brilliant

[gurbazdhillon]

Everything makes sense now! Thanks for the upload. Appreciate it.

[dr.nishachaudhary]

Consider thousands of likes from my side...
Damn youtube, it only permits one like, but you explained it excellently

[alishancharania]

Your tutorials are way better than those of my professors here. All the very best for your channel!! Love from Hong Kong <3

[robr]

This is the best YouTube video I’ve ever seen. Been looking for a channel like this for a long time. Thanks man, keep putting out great content.

[danielwalker]

Brilliant explanation. Will be pointing my students in this direction, for sure.

[erockromulan]

Thanks for the video! I'm writing code for a college project that finds mach numbers before and after the throat based on different area ratios, and this video really helped. It makes much more sense now!

[sacheewg]

I'm so happy that I found this channel. Thank you so much Josh

[JamesMaxwell-mi]

Definitely it was an awesome lecture for me. Thanks for your teaching and also your charming eyes.

[isxp]

Good lord this was insightful. Gas Dynamics final at 8:00 am tomorrow.