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DY: Fachverband Dynamik und Statistische Physik

DY 21: Granular Matter / Contact Dynamics

DY 21.7: Vortrag

Mittwoch, 13. März 2013, 16:45–17:00, H47

Measuring the Mechanical Properties of a Granular Suspension — •Chih-Wei Peng and Matthias Schröter — Max-Planck-Institute for Dynamics and Self-Organization

The mechanical properties of granular suspensions differ from normal liquids. Fluidized beds are often used to study such systems. By changing the flow rate, one can achieve different states, from suspension at high flow rate to solid-like sediment at low flow rate.

Our experiment system is a torsion pendulum which is partially immersed into a fluidized bed. We apply a sinusoidal magnetic field to drive the torsion pendulum. The complex susceptibility χ(ω) can be obtained by the ratio of driving torque and the response deflection angle, the latter being measured by a reflected laser beam and a quadrant photodiode. This ratio can be used to determine the viscosity of this system by using the Langevin equation.

Moreover, this method can also be applied to measure an effective granular temperature based on a fluctuation dissipation theorem.