Interactions of nonlinear pulses in convection in binary fluids

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Abstract
Several groups have recently reported a robust localized state of traveling waves in experiments on convection in binary fluid mixtures. These states resemble the ‘‘pulse’’ solutions of complex Ginzburg-Landau equations with subcritical bifurcations. We study the stability of these pulses experimentally by observing their interaction with high-frequency wave packets, which we inject into our annular convection cell by creating localized disturbances. We find that the spatial phase structure of pulses is central to their stability. An incident wave packet of sufficient amplitude can perturb the phase of the pulse so much that it loses stability and disappears, leading to a transition to a new state. Phase perturbations also determine the interactions between nearby pulses and the role of random fluctuations in the transition from a pulse state to a state in which slow traveling rolls fill the cell.