Related Experiment Video
Updated: Aug 10, 2026

Kinematic History of a Salient-recess Junction Explored through a Combined Approach of Field Data and Analog Sandbox Modeling
Published on: August 5, 2016
Structure formation and instability in a tube of sand
E G Flekkøy1, S McNamara, K J Måløy
1Department of Physics, University of Oslo, P.O. Box 1048 Blindern, 0316 Oslo 3, Norway.
Abstract:
A new instability in the combined flow of fine grains and gas is investigated by means of experiments, simulations, and analytic techniques. When a bubble of air rises through a granular packing in a tube, a sequence of smaller bubbles spontaneously forms in front of it. The existence of this instability is shown from the experiments, simulations, and theoretical considerations. Moreover, the simulations and experiments agree on the quantitative level. In particular, when the tube is tilted away from the vertical the experiments and the simulations show the same increase in the speed of the rising bubble.
Related Concept Videos
Entropy and Solvation
Destabilization of Microtubules
Microtubule Instability
The Colloidal State
Steady, Laminar Flow in Circular Tubes
Turbulent Flow

