I don't understand the reason behind the formation of Worthington jets
I've been reading a bit about Worthington jets Video 1, this phenomenon is caused when something is thrown to the water as we all have seen in swimming pools. This is also caused when a bubble comes from the bottom of a liquid and burst at the liquid interface Video 2.
Destin(SmarterEveryDay), a science youtuber demonstrated this effect Video 3 in his channel , but I don't understand the explanation of this effect, he claims at 0:53:
Destin: A cavity opens up and it's air and all that air has nowhere to go, so it slaps back together because there is a discontinuity in pressure
I don't understand what does he mean by "discontinuity in pressure"
I've been reading at this article STEPHANGEKLE AND J.M.GORDILLO, Generation and Breakup of Worthington Jets After Cavity Collapse [5]. There is a really interesting picture in page 5:
Here it's shown that suddenly when the two cavities separate, two jets appear in different directions, the article only says in page 3:
after impact a large cavity is created beneath the surface which subsequently collapses about halfway due to the hydrostatic pressure from the liquid bulk.
There is no information about the reason behind the generation of the Worthington jet, it seems to me that there is something like a restoring force when the two cavities separate.
I understand much less about Video 2, it seems to me that when the bubble explodes it generates some kind of wave that meet in the bottom of the bubble.
I just wanna get a rough understanding on the generation of this phenomena. Any help clarifying something related with the phenomenon is appreciated
