Comment by gcanyon
1 day ago
Thanks for the clear explanation, and you deserve a separate upvote just for that video link. "slightly" -- compared to what Tesla is claiming, sure, but 5+ bar is no joke -- "you'll put an eye out, kid"
I wonder if the shock waves visible in the video are still due to the converging-diverging aspect, just with no bell around the diverging part.
If we look at the flow lines, they converge and diverge even when the "nozzle" is a section of a pipe.
In rockets, there is a so called "aerospike" engine [1], which does not have any bell-shaped nozzle at all, but instead uses the ambient air to always shape the flow for an ideal expansion ratio. In theory it is great, but in practice it remained mostly a pie in the sky.
[1] https://en.wikipedia.org/wiki/Aerospike_engine