|Description||2022 Spring Physics Colloquium Series|
Dr. Jeff Olafsen
To Fall or Not to Fall: The Physics of Sandcastles
Imagine driving along a sandy beach at the water's
edge. On one side are dry dunes formed primarily
by the motion of the wind, and on the other is
the supersaturated sand beneath the rolling waves.
The sand beneath the water is strong, supporting the weight of the water above it, but not stable, changing as the waves roll back and forth on top of it. Conversely, the dry dunes are stable, but not strong, easily compacting under the weight of a person if one tries to walk across them.
Driving the car near the water's edge is the sweet spot where the sand is both stable and strong: Too far into the surf the car can become bogged down in the strong but unstable seabed, while too far into the dunes the car can become buried in the weakly structured sand pile that cannot support the
vehicle's weight. A low-dimensional 'phase space' energy model outlines contributions to the relative strength and stability of a jammed system from both granular structure and interstitial fluids as determined by experimental
parameters: particle sizes, critical angles, particle roughness, and relative
couplings. While the model does not include higher-order effects (spatial or temporal dependence of the parameters), it nonetheless demonstrates the
overall role that granular temperature plays in both the relative strength and stability of the system in a manner that allows the two parameters to be distinguished and independently evaluated. The model represents a significant step forward in the development of a universal predictive equation for understanding granular+fluid systems traversing the micro-, meso-, and macroscales.
For more information contact: Dr. B.F.L. Ward, 254-710-4878