DH> accent rate. Most computers and digital depth gauges have an accent
 DH> warning of some type to let you know your going to fast. Bubbles
 DH> are not that accurate.
 HM> I imagine that the rate the bubbles travel is also influenced by the 
water
 HM> temperature.
Ah!  An iteresting physics question!
I'm not going to take the time to work out the math (mainly since I don't 
know what box the books are buried in), but I'm going to guess that water 
temerature is a minor influence.  Two factors influence that guess.
First, the rule states "smallest bubble".  Since we are continuously 
breathing (a more important rule since  you shouldn't be ascending if you are 
not breathing out anyway) and bubbles grow (and break up) as they rise, a 
bubble doesn't remain the smallest bubble for very long.  That length of time 
defines how much heat can be transfered from the water to the air (or vice 
versa) across an interface that is notoriously poor for heat transfer (water 
- air).
Second, the compressed air goes through an expansion valve (the regulator) 
which cools it, then it is warmed somewhat and moisture is added in the 
ungs.
 These two actions are going to have profound affects on the air temperature. 
 The expansion because it's such a drastic step in the density profile of the 
air and the respirated moisture because it makes a step addition to the heat 
in the air.
With the huge amounts of energy transformations happening to produce the 
bubbles and the relatively short time a bubble remains the "smallest bubble", 
I can't see the water temperature having much of an affect.  It would be 
interesting to see the math and the heat transfers and how they affect the 
air expansion and bouyancy.  It would also be interesting to see the affect 
of salinity and altitude.
I'm guessing that the major affects are geometric. That the breathing 
apparatus is going to produce bubbles with some diameter being the smallest 
and the rate of ascent for that size of bubble is not going to vary more than 
a few percent regardless of the diving conditions in the recreational range 
-- probably close to imperceptable.
Viscosity of the fuid would have a most profound affect on the size of 
bubbles formed and their rate of ascent, but the range of viscosity is very 
narrow for recreational diving.  (I try to do most of my alcohol diving 
without a regulator and never, ever try to beat the bubbles to the surface 
)
Thanks for making me think, it got me awake without the help of coffee this 
morning.
-bry
--- Msg V4.5
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