We would like to find some equations to describe the motion of sand since at the present
there have not been any equations to describe this motion.
We have chosen a granular system with very liquid-like properties. For instance,
one of our main interests is working with sand as a fluidized bed. This is done by
flowing air up through the bottom of the sand. With different stresses either by vibrations
or airflow, the sand will become more solid-, liquid-, or gas-like. When the stress is low,
the sand remains solid-like. Yet when the stress is high, the sand becomes liquid- and
gas-like. There may be a range of stresses that make the sand behave as a simple liquid.
Narayanan Menon and Douglas J. Durian3 have found that at a low flow rate of air
coming up through the sand using small sand granule size, the sand will become
fluidized. Their main observation was that surprisingly even though you can easily stir
the sand, the grains do not move when left untouched (but fluidized). P. Geldart and A.
Y. Wong4 have used different sizes of sand in their experiments. They found that 106
m particles and smaller work best to make a fluidized bed. The sand appears fluid-like
(easily stirred, surface stays horizontal) without gas bubbles. As you turn up the flow