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W. G. Pritchard Lab Seminar: 11:15 AM - 12:15 PM, 106 McAllister Bldg

	             **Monday October 15, 2007**
	
Standing waves on moving bubbles

Andrew Belmonte

W. G. Pritchard Laboratories
Department of Mathematics
Penn State University, USA


Abstract:

How does a rapidly moving object enter a quiescent fluid? The experimental 
study of this problem parallels the development of high-speed imaging 
(Worthington, Edgerton), and recent studies show that there are still new 
things to be understood - even in water. I will present our experiments on 
the fluid impact of a solid sphere, which produces a cavity and 
subsequently an entrained bubble, a splash, and an audible PLUNK! We have 
found that this acoustic emission leads to coherent ripples on the bubble 
surface, which are fixed in the lab frame, and begin just after the pinch-
off ("deep seal") of the cavity. A potential flow model for a slightly 
compressible fluid explains these ripples as the spatial rectification of 
the acoustic bubble oscillations by the moving object. This is joint work 
with T. Grumstrup and J. B. Keller.

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