We consider time-averaged patterns obtained from the Kuramoto-Sivashinsky equation in a bounded domain. The average patterns recover global symmetries broken locally by the chaotic fluctuations. Their amplitude is strongest at the boundaries and decays with increasing distance to them. The law of decay is found and explained. The wavenumber selected by the average pattern is studied as a function of system size and the different behavior between the central and boundary regions is discussed. Most of these observations agree with experimental results in different systems, thus indicating a degree of universality in the behavior of average patterns.
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