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Old March 24th 04, 08:03 AM
Julian Scarfe
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In article ,
(Andrew Sarangan) wrote:

Is there an explanation for why small radii objects collect ice
faster? The NASA icing video simply states this fact without giving an
explanation. I have found the same with most other sources as well.


"Roy Smith" wrote in message
...

Here's a somewhat fuzzy/unscientific answer which may help at an
intuitive level...

A larger radius object disturbs the air a further distance out in front
of it than a smaller object does. So, if a water droplet is sitting
there suspended in the air, with the smaller object, it has less of a
chance to get deflected up or down before the object slams into it.


I don't think it's unscientific. It seems like a rather good scaling
argument. The critical parameter is the ratio of the radius of the droplet
to the radius of curvature of the object. For a very large ratio (e.g. 1,
think baseball-sized droplet vs wing), you wouldn't expect the object to be
much affected by the airflow around the object, and it will simply slam into
the object. For a very small ratio (e.g. 10^-6), the droplet will simply
follow the streamlines around the object. Thus it's clear that there is a
dependence there.

Julian Scarfe