Download Force Fluctuations in Collisional and Frictional Granular Flows

Force Fluctuations in Collisional and Frictional Granular Flows
E. Gardel, E. Seitaridou, E. Keene, N. Easwar (Smith College)
N. Menon (University of Massachusetts-Amherst)
What Makes a Flow Collisional or
Frictional?
What parameter(s)
drives the transition
between collisional
and frictional flow?
–  Geometry?
–  Material
Properties?
–  Dimensionality of
Packing?
–  Flow Velocity?
• 2D
• Glass and
Steel
• Vertical
Walls
• Varying
Widths
Transducer
WHAT
HAPPENS
TO
THE
FORCE INHOMOGENEITIES IN FLOW?
Voltage (V)
Typical
Force
Trace
1.0
Passage time, tp(~30t)
0.5
0.0
10
20
30
time
40
50msec
transducer
tp: typical passage time for single
particle to pass across transducer
Opening, a, can be adjusted
for different widths
t: average time interval between
colliisons
A particle experiences many collisions as it passes over the transducer
Motivation
2D at 18 cm/s
3D at 24 cm/s
Frictional
Collisional
Many short individual collisions
Enduring contacts as well as
collisions
Movies do not reveal such collisional activity
Smith
College
Physics
Department
Polymer
Poster
Symposium