Re: Need Help: Fluid Dynamics Question

When you say pressure I assume you mean pressure difference. The hole is
just a sharp edged orifice and friction losses are small. All that happens
is that the pressure difference approximately equals the dynamic head coming
out or:

Delta(p) = 0.5*Rho*V^2

So velocity is V = sqrt(2*Delta(p)/Rho)

It is fairly obvious that with the density of water being much greater than
that of air the velocity of the water will be much less.

At room temperature Rho = 1000 kg/m^3 for water and = 1.20 kg/m^3 for air.
The air will come out 1000/1.2 = 833 times as fast for the same delta(p) in
N/m^2

"John Smith" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> I am talking about the water and air under room temperature. I would like
to
> know how faster air flows than water through the same hole at the same
room
> temperature. I searched on the Internet. Some says that air flows 50
percent
> faster than water. I am not sure that information is correct or not.
>
> JS
>
>
> "Ed Ruf" <[EMAIL PROTECTED]> wrote in message
> news:[EMAIL PROTECTED]
> > On Sat, 13 Sep 2003 22:02:28 -0400, in sci.mech.fluids "John Smith"
> > <[EMAIL PROTECTED]> wrote:
> >
> > >Hi, can anybody answer the following question? Thanks.
> > >
> > >Under the same pressure and through the same size of a hole, which of
> these
> > >two: air and water, flows faster? Does it have something to do with the
> size
> > >of the hole (0.01 mm, 1 mm, or 10 mm),  the thickness of the hole (0.01
> > >mm, 1 mm, or 5 mm), or the pressure?
> >
> > When you say water, are you implicitly implying liquid water? If both
are
> a
> > gas, then the answer may be unintuitive.
> >
> > If air vs. water vapor and the pressure ratio across the hole is enough
> for
> > choked flow:
> >
> > Gamma for water vapor is slightly less than that of air at 70F, 1.37 vs.
> > 1.4. R for water vapor is 455 J-kg/K vs 287 for air.
> >
> > The sonic velocity ratio of air to water vapor for the same temperature
is
> > then
> > sqrt( R_air x gamma_air_ /R_wv x gamma_wv)
> >
> > or  sqrt ( 287 x 1.4 / 455 x 1.37) = 0.64,
> >
> > So in the case of choked (sonic) flow the velocity of water vapor is
> higher
> > than that of air.
> >
>
>