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Granular Materials: Liquid-like Properties of Sand - page 7 / 14

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In order to find the viscosity of the fluidized sand, we set the velocity of the motor

ranging from 0.06-1.5in/sec. We know the size of the ball that we used 2 different balls

with diameters of 0.748in and 1.5 in. The force transducer is measured in volts. In this

case, we must convert the force to Newtons. The calibration graph is show in figure 4.

Also, the gas flow rate is measured by the location in mm that the ball rises on the flow

meter. This must be converted into liters/m air (the conversion shown in figure 5) with

the function of y = -1.9252 + 41.8171x - 48.1052x2. This way we can calculate the

viscosity and notice if it is a constant or function of velocity. To do this, we move the ball

up and down the same distance and at the same velocity many times. The LabVIEW

program takes the average of the data each time to smooth fluctuations in the measured

force. To figure out the measured point from that graph, we subtracted the downward

force trace from the upward trace to obtain the actual average force at that velocity and

flow speed and divide by two.

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y = 0.063866 + 0.82358x R= 0.99994

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Fig 4

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force (N) This calibration graph shows the conversion of force measured in millivolts to Newtons.

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