Onset of Patterns in an Ocillated Granular Layer: Continuum and Molecular Dynamics Simulations - Condensed Matter > Soft Condensed MatterReport as inadecuate




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Abstract: We study the onset of patterns in vertically oscillated layers offrictionless dissipative particles. Using both numerical solutions of continuumequations to Navier-Stokes order and molecular dynamics MD simulations, wefind that standing waves form stripe patterns above a critical acceleration ofthe cell. Changing the frequency of oscillation of the cell changes thewavelength of the resulting pattern; MD and continuum simulations both yieldwavelengths in accord with previous experimental results. The value of thecritical acceleration for ordered standing waves is approximately 10% higher inmolecular dynamics simulations than in the continuum simulations, and theamplitude of the waves differs significantly between the models. The delay inthe onset of order in molecular dynamics simulations and the amplitude of noisebelow this onset are consistent with the presence of fluctuations which areabsent in the continuum theory. The strength of the noise obtained by fit toSwift-Hohenberg theory is orders of magnitude larger than the thermal noise influid convection experiments, and is comparable to the noise found inexperiments with oscillated granular layers and in recent fluid experiments onfluids near the critical point. Good agreement is found between the mean fieldvalue of onset from the Swift-Hohenberg fit and the onset in continuumsimulations. Patterns are compared in cells oscillated at two differentfrequencies in MD; the layer with larger wavelength patterns has less noisethan the layer with smaller wavelength patterns.



Author: J. Bougie, J. Kreft, J. B. Swift, Harry L. Swinney

Source: https://arxiv.org/







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