Interdisciplinary Seminar in Nonlinear Science

Title: Rayleigh-Benard convection with modulated acceleration
Speaker: Werner Pesch
Speaker Info: University of Bayreuth, Germany
Brief Description:
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Rayleigh-Benard convection with modulated acceleration Rayleigh-Benard convection (RBC) of a horizontal fluid layer driven by a temperature gradient, is one of the best studied paradigms of pattern formation in nonequilibrium systems. Time-periodic modulation of the acceleration (gravity force) by periodic vibration of the standard convection cell provides an interesting extension that allows the study of parametrically driven instabilities in this classic systems. We present a theoretical analysis of various competing pattern-forming mechanisms based on the underlying Boussinesq equations. Recent experiments of the case of vertical vibration have revealed a host of interesting patterns, for instance superlattices of stars on a square backbone. They exist near a codimension-2 point, where a harmonic response of the system switches to a subharmonic one, and are organized by a new four-mode resonance mechanism. The case of horizontal shaking is more involved since already the basic state is associated with a time- periodic shear flow. We will address briely the resulting competition between buoyancy-driven and shear-flow instabilities. Applying shaking in two perpendicular horizontal directions (rotating oscillatory acceleration) can lead to Kuppers-Lortz like domain chaos scenarios.
Date: Friday, June 03, 2005
Time: 2:00PM
Where: Tech M416
Contact Person: Hermann Riecke
Contact email: h-riecke@northwestern.edu
Contact Phone: 847-491-8316
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