SPATIALLY UNIFORM TRAVELING CELLULAR-PATTERNS AT A DRIVEN INTERFACE

We report on a study of asymmetric, traveling patterns which develop a t a driven fluid-air interface in the experimental system known as the printer's instability. We find that the traveling pattern appears via a supercritical parity-breaking transition, at which the pattern lose s its reflection symmetry and begins to drift with constant speed. Fro m measurements of the degree of asymmetry of the drifting pattern as a function of the experimental control parameter, we find that the asym metry increases with the square root of the control parameter, and tha t the drift velocity is linear in the asymmetry. This behavior is in a ccord with recent theoretical predictions. Our results do not agree, h owever, with the predictions of a model of the parity-breaking transit ion involving the coupling of spatial modes with wave numbers q and 2q .