Granular dynamics

Categories: Current Research
Granular media are of importance in the chemical and pharmaceutical industry, where powdered chemicals are mixed and transported. We have designed novel experiments using simplified flow configurations where the flow of sand can be compared to that of a liquid. These include a layer of sand inside a rotating cylinder, as well as the motion of granular layer after the impact of a solid sphere. We have studied granular jetting when an impact cavity closes up under the influence of gravity. Such jets, known as Worthington jets, are well-known during impacts onto liquid surfaces. This discovery therefore allows for detailed comparison between the two media.

We are pursuing a similar approach for spheres impacting onto granular beds, where the ejecta are compared to those in liquid impacts. The long-term goal of this research is to formulate constitutive relations for rapidly flowing granular media.
  1. Marston, J. O., Li, E.Q., Thoroddsen, S. T. (2012). Evolution of fluid-like granular ejectas generated by sphere impactJ. Fluid Mech.704, p. 5-36.  Including a focus on fluid article and a cover image of this issue.
  2. Marston, J. O., Vakarelski, I. U. and Thoroddsen, S. T. (2012). Sphere impact and penetration into wet sandPhys. Rev. E86 020301.
  3. Thoroddsen, S. T. & Shen, A. Q. (2001). Granular jets.  Phys. Fluids13, 4-6