A v a l a n c h e

D y n a m i c s

a n d

D e f e n ce

TIME_S

Figure 6. Recordings of the snow flow experiment. a: air flow velocities measured with the static pressure depression at 0.17 m and 0.42 m in
height; solid lineshows the former and dotted line latter.b: Impact pressure at 0.14 m.

1/6 forthree dimensional systems;it fit his avalanche ex-
periments with the styrene foam particles ( 1.5-2.0 mm in
diameter).Figure 10 proves clearly that the above theory
gives good account for these ping-pongball flows as well.
In the experiments, with increasingthe number of balls,
we couldrecognizea headandtail structuremore andmore
clearly.Figure11givesa picture ofhead when 250,000
ballswerereleased. Herethe thicknessofthehead was
higher than60 cmwhichcorrespondedto about 40 particles
diameter. Althoughthe individualball changedthe mutual
position rapidly, the leadingedgelooked to flow down like

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