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SUMMARY:Washboard Road: The dynamics of granular ripples - Prof Jim McElwa
 ine\, BA\,MA\,MMath\,CASM\,PhD\, Professor of Geohazards\, 	    Department
  of Earth Sciences\, Durham University and the Planetary Science Institute
  Tucson
DTSTART:20140116T160000Z
DTEND:20140116T173000Z
UID:TALK49205@talks.cam.ac.uk
CONTACT:Anama Lowday
DESCRIPTION:Granular surfaces tend to develop lateral ripples under the ac
 tion\n  of surface forces exerted by rolling wheels\, an effect known as\n
   washboard or corrugated road.  We report the results of both\n  laborato
 ry experiments and soft-particle direct numerical\n  simulations.  Above a
  critical speed\, the ripple pattern appears as\n  small patches of travel
 ing waves which eventually spread to the\n  entire circumference.  The rip
 ples drift slowly in the driving\n  direction.  Interesting secondary dyna
 mics of the saturated ripples\n  were observed\, as well as various ripple
  creation and destruction\n  events.  All of these effects are captured qu
 alitatively by 2D soft\n  particle simulations in which a disk rolls over 
 a bed of\n  poly-disperse particles in a periodic box. These simulations s
 how\n  that compaction and segregation are inessential to the ripple\n  ph
 enomenon. We show how a simplified scaling model gives insight\n  into the
  mechanism of the instability and discuss the applicability\n  of a weakly
  non-linear theory. \n
LOCATION:Engineering Department - Lecture Room 4
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