On Tue, 28 Feb 2006, Mike Hord wrote:

> I'd like to make some fountains for my home, and I'm wondering
> if anyone has any input.
>
> In particular, I'm wondering about an equation describing the
> behavior of a stream of water emerging from a hole in a
> reservoir.  Google search terms are proving elusive.  It seems to
> me that the equation should be pretty simple, based on depth
> of water and size of hole.  The result should be a half-parabola.
>
> Anyone have any ideas?

It depends a lot on the discharge speed. At low speed you get a piece of 
a parabola, at higher speeds the air brakes the water seriously and you 
get something else. Also look up vena contracta and the Bernoulli 
equation, and Reynolds numbers. If the diameter at the vena contracta is 
too low wrt. the speed of the flow you get pulverisation instead of a 
jet. This can be fixed by using a proper nozzle which produces the vena 
contracta under control (of the nozzle walls). The Reynolds number 
predicts the type of behavior (based on speed, density and the 
dimensions of the jet). The short version of this is, that there is no 
such thing as a long range, low volume jet. At least not with normal 
liquids (like water).

Peter
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