title: Stability balloon for two-dimensional vortex ripple patterns.
abstract: Patterns of vortex ripples form when a sand bed is subjected to an oscillatory fluid flow. Here we describe experiments on the response of regular vortex ripple patterns to sudden changes of the driving amplitude a or frequency f. A sufficient decrease of f leads to a "freezing" of the pattern, while a sufficient increase of f leads to a supercritical secondary "pearling" instability. Sufficient changes in the amplitude a lead to subcritical secondary "doubling" and "bulging" instabilities. Our findings are summarized in a "stability balloon" for vortex ripple pattern formation.
authors.affiliation: Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen, Denmark.
authors.forename: J L
authors.initials: JL
authors.lastname: Hansen
authors.forename: M
authors.initials: M
authors.lastname: van Hecke
authors.forename: C
authors.initials: C
authors.lastname: Ellegaard
authors.forename: K H
authors.initials: KH
authors.lastname: Andersen
authors.forename: T
authors.initials: T
authors.lastname: Bohr
authors.forename: A
authors.initials: A
authors.lastname: Haaning
authors.forename: T
authors.initials: T
authors.lastname: Sams