Re: AAT:Questions

H. M. Hubey (
9 Oct 1995 19:07:11 -0400 (George Black) writes:

>> Sorry, but when I took SCUBA training, one of the things we
>>learned is that there is _no such thing_ as "warm water diving." Even
>>tropical surface waters cause chills, exhaustion, and hypothermia in a
>>few hours. The human body shows _no_ adaptation to deal with the kind
>>of long-term immersion that AAH would require.

>Hurrah, (and may I add) as a sports diver for a number of years -- one of the
>things that no-one has mentioned here is the thermocline.
>The energy of the swimmer/wader/diver is compromised by the chill factor, the
>workload (working against the tides, wave action, etc)

Well, actually it's like this, with some historical background:

Until around 1920's when Prandtl started to get some good results
the field of hydrodynamics was kind of schizoid. On the one hand
we had the engineering and experimentalists working with data
from experiments (except for some simple results from Bernoulli
equation). The scientific part consisted of the Navier-Stokes
equations which nobody could solve for any real life case and
if they did solve them with some approximations they didn't fit
the data.

It was at this time that Prandtl started his work on "Boundary
Layer Theory". There is a thin layer of air/water that clings to
our surfaces, and the temperature drop from our skin to the
ambient temperature is steepest in the boundary layer and this
layer sort of acts as a insulation. If wind/convection takes
away the boundary layer more heat starts to escape because the
temperature gradient has now increased.

so in windy weather, the "chill factor" is added to make the
ambient temperature closer to what we'd feel (based on our
heat loss) if there was no wind/convection.

What does this have to do especially with water immersion and
not being in air? Nothing except that the conductivity
coefficient changes.


Regards, Mark