Effects of shearing flow with inertia on monolayer mesoscale structure

In an experimental flow system capable of imparting a well-controlled shear-rate distribution with inertia to a monolayer consisting of coexisting phases, we have studied the resulting phase morphology and domain fragmentation. These evolve on distinct time scales: the viscous time associated with the viscosity in the bulk and the Marangoni stress and the fragmentation/relaxation time associated with the phase morphology. A relationship between the microstructure (line tension) and macroflow (shear rate) determining the meso length scale of the coexisting phase domains has been deduced from dimensional analysis and was found to correlate well with the quantitative experimental observations.

Three-dimensional modes in a periodically driven elongated cavity

Three-dimensional instability modes of the periodic flow in a rectangular cavity driven by the harmonic sliding oscillation of its floor are explored experimentally. Theory for a cavity with infinite span predicts two synchronous modes and a quasiperiodic traveling-wave mode as primary transitions from two-dimensional to three-dimensional flow for different combinations of floor oscillation amplitude and frequency. Previously, only one of the two synchronous modes had been found experimentally. Here, we provide experimental details of both synchronous modes and a quasiperiodic mode. All three modes appear in the parameter regimes predicted by the theory; however, in the finite-span experiments, the traveling wave nature of the quasiperiodic mode is replaced by a nonpropagating mode with spatial features similar to those of the traveling mode.