Ratcheting States of Cellular Flames
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A premixed flame on a circular porous plug burner appears a thin (0.5 mm) luminous disk. Premixed flames are distinctive as a dynamical system in that both the spatial and temporal characteristics of the can be measured to high resolution. Cellular flames of rich hydrocarbon-air mixtures form ordered states of concentric rings of brighter, hotter cells separated by darker, cooler cusps and folds. At larger values of the control parameters, the ordered states are observed to bifurcate to dynamic states: 1) rotating states in which rings of cells undergo rotation (~100 deg/sec), 2) hopping states in which individual cells abruptly change their angular position in a hopping-like motion, 3) intermittently ordered states in which ordered patterns intermittently appear and disappear at irregular intervals, and 4) ratcheting states in which rings of cells rotate very slowly (~1 deg/sec), speeding up and slowing down in a manner characteristic of each state. Fluid dynamics videos of each state will be shown. This dynamics will be discussed in the language of dynamical systems.
MPEG-1 Video of Dynamic States of Cellular Flames