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Granular Materials: Liquid-like Properties of Sand - page 5 / 14

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tube in order to hold the sand, yet allow the air to flow through the frit into the sand.

Sand is put into the glass tube that are sphere glass beads sizes of 63-106 m diameter.

Air is pushed through the frit from a flow meter through a heater at 205 F to fluidize the

sand at certain flow rates. The heater is used to drive off water vapor in order to prevent

sticking or clumping. For example, in sandcastles, wet sand seems to use water as glue to

hold the sand together, and as it dries the sand collapses into its many small pieces. This

is why heating the sand is important. A ball is attached to a nylon wire (.01 in thick) that

is then attached to a force transducer on a translation stage. The translation stage is

connected to a stepper motor with a flexible shaft. The force transducer is attached to a

Stanford Research Systems lock-in amplifier model SR830 DSP. The lock-in amplifier

and motor controller are both connected to a computer that is programmed using

LabVIEW. LabVIEW is programmed to move the translation stage up and down with

certain velocities and receive data from the force transducer, which measures the force

needed to drag the ball through the sand

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