Dennis J. Young
djyoung at UCSD.Edu
Wed Mar 13 18:32:32 EST 2002
Since the nozzle orifice is probably not exactly 70 microns, I used an
accurate volume measurement (100,000 drops repeated 10 times, 3.3% c.v) to
calculate back to the jet diameter (assuming spherical drops) and got a
*jet* diameter of 66.95 microns.
3.53j^3 = 4pi/3(d/2)^3 yields drops with diameter 1.8891 times the jet (as
Joe Trotter pointed out)
From Pinkel and Stovel, the jet relaxes to as much as 0.866 times its
initial diameter. I got about 0.956
At 07:18 PM 3/11/2002 -0500, Howard Shapiro wrote:
>Alice Givan wrote-
>>In my comment on calculating the volume of a droplet, I "guessed" that
>>the diameter of
>>the drop might be approximately the diameter of the nozzle orifice. I
>>knew this was a
>>rough approximation --- as the stream can contract a bit as it leaves the
>>then the droplet that forms can have a diameter greater than the diameter
>>of the stream.
>>Joe Trotter (whom I always trust) says that the droplet diameter is
>>times the nozzle diameter. In fact, I just went and measured the drop and
>>on my monitor screen and I got about 1.6 (using a bad ruler and a roughed
>>of paper). So my approximation that the drop diameter was equal to the
>>diameter was, obviously, grossly wrong either way.
>I wouldn't have gone that route.
>> Perhaps the best way to calculate
>>the volume of a drop is by Dirk Van Bockstaele's method (calculating the
>>of the "column" of liquid coming out of the nozzle in one second and then
>>that volume into however many drops are being generated in one
>>second). However, in
>>order to do this from first principles you need to know the diameter of
>>the stream and
>>also the velocity of the stream.....possible, but awkward.
>Velocity for a stream-in-air nozzle, in m/sec, should be 3.7 * (sheath
>pressure(in psi))^(1/2). This is from Pinkel and Stovel, also on p. 139
>of the 3rd Ed. of PFC. Page 140 has the "column" volume calculation.
>> I suppose you could also
>>do it simply by measuring the volume flowing from the stream in 10 minutes
>>calculating the volume for one second (I might be missing something here
>>where are you (I know, he is working on the fourth edition just when I
>I'm still here, obviously. And you can probably limit the calculation of
>stream volume to 1 minute; you'll divide by 60 to get the volume per
>second, and you'll get enough volume out in a minute (or two) to get an
>accurate enough calculation.
>And there's time (but not much) to clear this up in the 4th Edition. Do
>you have a reference to Dirk van Bockstaele's calculation?
Dennis J. Young
Flow Cytometry Core Facility
University of California, San Diego
Internal Medicine Group, Bldg #4, Room 126
9500 Gilman Drive
La Jolla CA 92093-0671
Mail:<<mailto:djyoung at ucsd.edu>>
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