For OP's specific context, alive and live are effectively synonyms (meaning living, not dead). The main difference is that, as OED points out, alive occurs chiefly in predicative use (after a verb)...
This animal is alive
...as opposed to adjectival live, used attributively (before a noun) in the semantically equivalent...
This is a live animal
Note that this distinction only applies in contexts where the living sense is both literal and specifically focusses on gross physical attributes, such as the ability to act/move autonomously. Thus, for example,...
This yoghurt is live / It is live yoghurt
...are both relatively "standard" usages. Attributive use of alive is uncommon, so no-one is likely to say "This is alive yoghurt" in any context. But if we consider these two alternatives...
1: This cheese is live
2: This cheese is alive
...most people would interpret #1 the same as the yoghurt examples (i.e. - the micro-organisms which made the cheese in the first place are still living within it). But #2 would probably be interpreted as a facetious allusion to a very mature, runny Camembert, slithering around the plate like a living thing. Or perhaps a truly disgusting cheese as per the more "figurative" usage...
I'm not eating that! It's alive with maggots!
...where alive implies visibly moving in and on it (also crawling with maggots), again with the "whole living organism" sense.
Where the sense is even more figurative (live = real-time, not recorded, for example), live is normally used in both contexts...
This news report is live (being broadcast as events happen)
It's a live news report (has exactly the same meaning).
TL;DR: OP's teacher is quite correct - native speakers would normally say is alive when they literally mean has not [yet] died, because it's an "attributive" usage.
Shrink can work. I would also consider "compress" as a good option. "Reduce" can also work
I reduced the plot vertically
You could ask this on English Language and Usage to get additional ideas.
Best Answer
If you need a purely technical term, you might try looking up laminar flow.
From Wikipedia:
P.S. I've just recalled the word unperturbed. Checking for "unperturbed stream", "unperturbed flow" on Google brings up not that many results, but let it be here, just in case.