For yet seven days, and I will cause it to rain upon the earth forty days and forty nights; and every living substance that I have made will I destroy from off the face of the earth.
KJV GEN 7:11-12 writes:
In the six hundredth year of Noah's life, in the second month, the seventeenth day of the month, the same day were all the fountains of the great deep broken up, and the windows of heaven were opened. And the rain was upon the earth forty days and forty nights.
KJV GEN 7:20...24 writes:
And the waters prevailed upon the earth an hundred and fifty days [...] Fifteen cubits upward did the waters prevail; and the mountains were covered.
KJV GEN 8:2-3 writes:
The fountains also of the deep and the windows of heaven were stopped, and the rain from heaven was restrained. And the waters returned from off the earth continually: and after the end of the hundred and fifty days the waters were abated.
Pretty light on detail and not much of a model. The problem is that this opens up every crackpot to expand on what the "fountains of the deep" and "windows of heaven" actually are, without any supporting evidence. The problem is even further exacerbated by the fact that whatever 'theory' they come up with can be claimed as being "supported by scripture".
In the end, what one usually ends up with is a finger snap of "God Did It". Which is fine, as long as one admits that they don't actually have any evidence, and don't go trying to twist what we know of history and geology into the flood narrative.
Alas, "mechanisms" for this normally end up being less believable than the technobable of your average star trek episode.