cool_hardware52:
Would it be possible to create this low pressure area without creating any vapor? Seems unlikely.
Tobin
But so what? As in the bicycle pump analogy, the creation
of vapors doesn't really impact the creation of the vacuum
-- it just keeps it from being a perfect vacuum. I just
like to be clear on it because some people think that
if the vapor weren't created, it won't be possible to pull
back the piston -- that the piston can only be pulled back
because the vapors alleviate the pressure. This simply
isn't so. The vapors are a artifact to the process.
In an exaggerative analogy, it would also be unlikely to be
able to cavitate without perturbing the earth's wobble
on her axis, since the earth's mass is being redistributed,
that doesn't tie earth axis wobble by definition to
cavitation.
Another analogy would be to consider the water replaced with
a bunch of ball bearings. If you put a prop in there and
spin it hard, you'll get cavitation, even if a couple ball
bearings do fly through the cavity. Now repeat the whole
thing in a vacuum. Those few ball bearing flying through
the cavity isn't what allows the void to be created.
They're part of the story, but not part of the definition
of the cavitation.
Regards,
--Mike
