| Mon May 25th 2009 16:00 HR Z203 | Seminar | The inside of a sandpile: 3D imaging of particle motion in dense granular flows Wolfgang Losert |
Details:Granular materials such as sand exhibit a striking ability to serve as either a strong solid or fluid. In the solid state the grains are jammed against each other unable to move, whereas in the fluid state grains rearrange relative to their neighbors. The transition between jamming and flow is hard to predict and model, in part due to the lack of direct observations of particle motion on the inside of a granular material. We pioneered a new approach to 3D imaging of particle rearrangements on the inside of a granular material and have applied this technique to study granular compaction, shear flow, and segregation. Imaging the motion of all particles allows us to fully characterize how a particle moves relative to all its neighbors when undergoing these processes. In compaction, we show that particle motion is correlated with the shape of the local free volume. We also image for the first time the motion of all particles during segregation in a mixture of large and small particles. We will discuss the implications of these observations for continuum models of granular flow. | ||
