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Morphology of Experimental and Simulated Turing Patterns

Morphology of Experimental and Simulated Turing Patterns

Morphology of Experimental and Simulated Turing Patterns

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Abstract<strong>Turing</strong> patterns formed in the chlorite-iodide-malonic acid (CIMA) reaction, a farfrom equilibrium chemical reaction-diffusion system, are morphologically comparedto patterns obtained in the Lengyel-Epstein (LE) model, which is based on a nonlinearpartial differential equation <strong>and</strong> believed to model the CIMA reaction.A quantitative morphological analysis via Minkowski functionals, inspired by thework <strong>of</strong> Mecke (PRE, 53(5)), shows significant differences between the concentrationpr<strong>of</strong>iles <strong>of</strong> patterns in the CIMA reaction <strong>and</strong> the LE model. This indicatesthat the deterministic LE model, while reproducing the basic character <strong>of</strong> the CIMAreaction, does not reproduce the correct concentration pr<strong>of</strong>iles.The concentration pr<strong>of</strong>iles measured in the experiment are given as 2D greyscaleimages for the CIMA reaction. The LE concentration pr<strong>of</strong>iles are obtained by solvingthe corresponding reaction-diffusion equation numerically using a finite-differencemethod.Minkowski functionals are morphological measures from integral geometry <strong>and</strong> characterizethe morphology <strong>of</strong> greyscale images. Our analysis shows that the CIMA <strong>and</strong>LE patterns differ in all Minkowski functionals, when extended fractions <strong>of</strong> patternsare analyzed. However a local agreement between crystalline, i.e. more ordered parts<strong>of</strong> the experimental patterns, <strong>and</strong> the patterns obtained in the LE model is found.We have excluded the possibility that additional additive white noise in the reactiondiffusionequations leads to an agreement <strong>of</strong> numerical <strong>and</strong> experimental patterns.An extended model based on the statistical superposition <strong>of</strong> basic patterns obtainedfrom the LE model produces patterns with a good morphological agreement tothe experimental hexagonal <strong>and</strong> lamellar <strong>Turing</strong> patterns. It also reproduces, forthe first time, the morphology <strong>of</strong> the turbulent phase, identified by Ouyang <strong>and</strong>Swinney (Chaos, 1(4)). This indicates that turbulent patterns could be describedas a dynamically fluctuating superposition <strong>of</strong> basic patterns.5

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