My instinctive, native-speaker interpretation here was 'the way the behave when challenged by a pressure transient' (= surge) — that would be the most natural interpretation I can think of of the word order as given — though by no means the only possiblity.

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Note added at 1 day 13 hrs (2019-02-22 06:38:53 GMT) Post-grading
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@ Asker
I'm afraid I thiink you are wrong there! If this is some kind of vessel or other system that has to withstand pressure, both statically and dynamically, then what we are interested in is how it 'behaves' when subjected to 'pressure transients' (= surges) — and this is precisely what the EN word order implies.

'Pressure' per se doesn't really exhibit 'behaviour'

I repeat, in case I haven't been clear: this is the way something else behaves as a result of transient changes in pressure.

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Note added at 1 day 15 hrs (2019-02-22 08:41:03 GMT) Post-grading
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@ Asker

No, I'm sorry, but again you are misunderstanding it!

It is not about 'how pressure transients behave' (broadly, they don't!) — here, I am convinced it is about 'how [something] behaves when confonted with a pressure transient'.

We find the same sort of thing in an electrical field, where we might talk about how some particular system behaved (reacts) to voltage or current transients, for example. Perhaps it would help you to try reserachin in e.g. this field, to get a feel for how it works?

You need to consider it as 'behavior (in the presence of) pressure transients' or 'pressure transient (-induced) behavior' — does that make it clearer?