49 research outputs found
Microscopic dissipation in a cohesionless granular jet impact
Sufficiently fine granular systems appear to exhibit continuum properties,
though the precise continuum limit obtained can be vastly different depending
on the particular system. We investigate the continuum limit of an unconfined,
dense granular flow. To do this we use as a test system a two-dimensional dense
cohesionless granular jet impinging upon a target. We simulate this via a
timestep driven hard sphere method, and apply a mean-field theoretical approach
to connect the macroscopic flow with the microscopic material parameters of the
grains. We observe that the flow separates into a cone with an interior cone
angle determined by the conservation of momentum and the dissipation of energy.
From the cone angle we extract a dimensionless quantity that
characterizes the flow. We find that this quantity depends both on whether or
not a deadzone --- a stationary region near the target --- is present, and on
the value of the coefficient of dynamic friction. We present a theory for the
scaling of with the coefficient of friction that suggests that
dissipation is primarily a perturbative effect in this flow, rather than the
source of qualitatively different behavior.Comment: 9 pages, 11 figure