Considerable effort has been expended in an effort to understand how granular materials behave during flow. To extend the current understanding, I have conducted experiments that involve a small amount of a granular medium in a series of horizontal rotating cylinders. With proper combination of humidity, grain size, mass of the granular medium and the rotation rate of the cylinder, I discovered a number of interesting wave patterns. Among these were states in which the granular front displays a spatially periodic arrangement of fingers. In addition to my experimental work, I have developed a theoretical framework that predicts the observed flow patterns followed by the numerical simulations. Furthermore, inspiried by the similarity between our lab scale fingering patterns and the aeolian geomorphology observed in nature, I extended my model to a continum phenomeno logical model to describe the ripple formations in nature. See Movie

  • E. Fried, A. Q. Shen, S T. Thoroddsen, Wave patterns in a thin layer of sand within a rotating horizontal cylinder, Physics of Fluids 10 (1998), 10--12.
  • A. Q. Shen, E. Fried, S. T. Thoroddsen, Is segregation-by-particle-type a generic mechanism underlying finger formation at fronts of flowing granular media, Particulate Science and Technology, 17 (1999), 141--147.