Andrew Dougherty

DRIVEN INTERFACES IN DISORDERED MEDIA : DETERMINATION OF UNIVERSALITY CLASSES FROM EXPERIMENTAL DATA

Interface motion in a random medium presents us with an archetype problem, with direct impact on various phenomena in condensed matter physics, including fluid flow in porous media [1], domain growth in disordered magnets [2], and flux lines in disordered superconductors [3]. In particular, much attention has been focused on understanding the morphological evolution of an interface driven through a disordered medium. Twophase fluid flow experiments have provided evidence that the morphology of the interface can be either selfsimilar or self-affine [4]. The self-similar morphology has been successfully described by various percolation based models, such as invasion percolation [1]. The motion and roughening of self-affine interface morphologies can be quantified by the global interface width wsL, td, where L is the system size. The study of discrete models and continuum growth equations leads to the observation that the width follows [5,6]

Measurement of the capillary length for the dendritic growth of ammonium chloride

Abstract We report the results of a new method of measuring the capillary length for the dendritic crystal growth of non-faceted materials. This method uses a nearly spherical crystal held near unstable equilibrium in an oscillating temperature field. For the growth of ammonium chloride crystals from aqueous solution, previous published estimates of the capillary length varied by over a factor of 20. With this new method, we find the product of the diffusion constant and capillary length Dd 0 to be 0.78 ± 0.07 μ m 3 / s , similar to that obtained for ammonium bromide crystals.

Identification of radius-vector functions of interface evolution for star-shaped crystal growth

This article introduces a new method based on a radius-vector function for identifying the spatio-temporal transition rule of star-shaped crystal growth directly from experimental crystal growth imaging data. From the morphology point of view, the growth is decomposed as initial conditions, uniform growth and directional growth, which is represented by a static polynomial model based on the Fourier expansion. A recursive model is also introduced to help understand the dynamic characteristics of the observed systems. The applicability of the proposed approach is demonstrated using data from a simulation and from a real crystal growth experiment.