SESSION Il
«=... DISCUSSION |
FRIEDLANDER: I would like to begin by asking Dr. Owe Berg a ques-
tion,
Near the end of your discussion, you said that you would not
expect drops to coalesce unless they were charged, that generally you
expect rebound to occur. That seems like a sweeping statement. Can
you amplify your remarks ?
OWE BERG: It was shown by Lord Rayleigh in 1890 that such is
the case. He used droplets produced by jets. Colliding drops coalesced
when charged; otherwise they bounced.
FRIEDLANDER: There must be kinetic-enersy considerations
I
you just have a few drops located next to each other, presumably they
will coalesce?
OWE BERG: The duration of the contact in elastic collision depends only slightly upon the impact velocity. The coalescence must
occur during the period of contact; otherwise bouncing occurs. I am
aware of experiments showing coalescence in all collisions, but the
charges on the drops were not controlled in these experiments. It is
very difficult to produce uncharged drops.
BOLIN: Dr.
Friedlander,
the rate with which the spectrum you
obtain in your work will be approached depends, of course, upon the
total number of particles per unit volume. Furthermore, you have assumed that no settling of the particles takes place; this is correct only
if the distance traveled by the particles is short during the time re-
quired to approach the equilibrium spectrum that you derive. Can you
estimate for which particle concentrations and sizes your theory is
valid?
FRIEDLANDER: The theory we have worked out so far applies to
nonsedimenting systems. We have checked it experimentally with an
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