Impact on soft sand: void collapse and jet formation.
Very fine sand is prepared in a well-defined and fully decompactified state by letting gas bubble through it. After turning off the gas stream, a steel ball is dropped on the sand. On impact of the ball, sand is blown away in all directions ("splash") and an impact crater forms. When this cavity collapses, a granular jet emerges and is driven straight into the air. A second jet goes downwards into the air bubble entrained during the process, thus pushing surface material deep into the ground. The air bubble rises slowly towards the surface, causing a granular eruption. In addition to the experiments and the discrete particle simulations we present a simple continuum theory to account for the void collapse leading to the formation of the upward and downward jets.
Lohse
Detlef
D
Faculty of Science and J. M. Burgers Centre for Fluid Dynamics, University of Twente, 7500 AE Enschede, The Netherlands.
Bergmann
Raymond
R
Mikkelsen
René
R
Zeilstra
Christiaan
C
van der Meer
Devaraj
D
Versluis
Michel
M
van der Weele
Ko
K
van der Hoef
Martin
M
Kuipers
Hans
H