Understanding an hourglass, and other granular flows in under an hour

Flows of particulate material, such as sand discharging in an hourglass, are ubiquitous in nature and industry. The flow and transport of granules, powders, or grains is complex and can differ considerably from that associated with a single-phase material. This presentation will highlight some unique features of granular materials (such as the discharge from an orifice) and describe some recent work at Caltech on wave propagation, booming sand dunes, and granular flow rheology.