Stability balloon for two-dimensional vortex ripple patterns.
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.
Hansen
J L
JL
Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen, Denmark.
van Hecke
M
M
Ellegaard
C
C
Andersen
K H
KH
Bohr
T
T
Haaning
A
A
Sams
T
T