Re: Explosive decompression - how fast?

On 2008-04-26, Dr J R Stockton <jrs@[EMAIL PROTECTED]
> wrote:
> A worst case approximation is that a transition between 10^5 Pa and
> 0 Pa propagates past her at 330 m/s.  So, per square metre, she gets
> 10^5 N for a duration of T/330 s, where T is her thickness in
> metres.

The duration is much longer than that, since she is still in the path
of the air escaping from further back in the airlock.  Even though the
static pressure is at 0 Pa, it still has significant density.

In particular, if c is the usual speed of sound, and v is the speed to
which the rarefaction wave accelerates the air, simple conservation of
mass puts the density ratio at c/(c+v).

So the air rushing past her from further in the airlock will exert
pressure as it escapes past her.  So for a long airlock, her velocity
would asymptotically approach the free outflow speed.


This is a fairly short airlock, but certainly longer than her average
thickness.


- Tim