Stability balloon for two-dimensional vortex ripple patterns - art. no. 204301

Patterns of vortex ripples form when a sand bed is subjected to an oscillat ory fluid flow. Here we describe experiments on the response of regular vor tex ripple patterns to sudden changes of the driving amplitude a or frequen cy f. A sufficient decrease of f leads to a "freezing" of the pattern, whil e a sufficient increase of f leads to a supercritical secondary "pearling" instability. Sufficient changes in the amplitude a lead to subcritical seco ndary "doubling" and "bulging" instabilities. Our findings are summarized i n a "stability balloon" for vortex ripple pattern formation.