title: Wavelength scaling of spiral patterns formed by granular media underneath a rotating fluid
abstract: A spiral pattern formed by granular media underneath a rotating fluid is discussed. Results from a cellular-automaton model are compared to experimental data, and are found to reproduce experimentally observed scalings. A theoretical argument predicting these scalings on the basis of the existence of a critical threshold condition is advanced. It is suggested that the pattern is probably not associated with a hitherto unknown flow instability, as has been speculated previously. It appears that the pattern constitutes some rotating analog to sand ripples in nonrotating systems.
authors.affiliation: Fluid Dynamics Research Centre, School of Engineering, University of Warwick, Coventry, United Kingdom.
authors.initials: F
authors.lastname: Zoueshtiagh
authors.initials: PJ
authors.lastname: Thomas