Re: [Phys-l] Coalesing drops

[Philip Keller <PKeller@holmdelschools.org>]

I think I missed the opening of this thread.  But a falling drop does not have to overtake a preceding drop.  It can collide with the smaller drop that recoils from the surface of the water.  I didn't know that recoil happened until I saw this amazing video earlier this week:

http://www.flixxy.com/water-drop.htm

The video does not show the interactiion with a second falling drop.  I wish it did.
________________________________________
From: phys-l-bounces@carnot.physics.buffalo.edu [phys-l-bounces@carnot.physics.buffalo.edu] on behalf of LaMontagne, Bob [RLAMONT@providence.edu]
Sent: Friday, October 08, 2010 10:25 PM
To: Forum for Physics Educators
Cc: Nancy Seese; Paul Doherty; T.K.Wang & Mary Brooks
Subject: Re: [Phys-l] Coalesing drops

Just curious - what do you mean by "The smaller will catch up and likely coalesce instead of shatter."?  My understanding is that the fall speed of droplets is proportional to the square root of their radii. Don't larger drops catch up with smaller ones?

Bob at PC


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From: phys-l-bounces@carnot.physics.buffalo.edu [phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of Bernard Cleyet [bernardcleyet@redshift.com]
Sent: Friday, October 08, 2010 4:33 PM
To: Forum for Physics Educators
Cc: Nancy Seese; Paul Doherty; T.K.Wang & Mary Brooks
Subject: [Phys-l] Coalesing drops

Becoming pop. is photographing splashing and drop collisions -- my thinking such is a development of an interactive exhibit at the Exploratorium.

Index of /images/Drops at the Exploratorium



And a device for such is marketed by Bryan Mumford.


Water Drops


This leads to my question posed to a friend and his answer:



> You will have no time in 3 or 4 feet for a small drop to "catch up" to a larger drop. The collisions are caused only by a later drop colliding with the spout of an earlier drop.
>
>
> > X!
> >
> >
> > I've noticed no drop collisions w/o reflection.   If one has two successive closely spaced drops, one may cause them to collide if the first is larger.  The smaller will catch up and likely coalesce instead of shatter.


I'm abut to, assuming (bad) Stoke is applicable, what reasonable differing sized drops would succeed.  I pose the question as interesting, I pray.


bc  thinks a quadratic dissipation would be more accurate, and would more likely give a favourable result.






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