Side-branch growth in two-dimensional dendrits. Part I: Experiments

Year: 2005
  • Couder, Y.
  • Maurer, J.
  • González-Cinca, R.
  • Hernández-Machado, A.
Journal: Physical Review E Volume: E71
Pages: 031602-1-031602-12
ISSN: 1539-3755
The dynamics of growth of dendrites’ side branches is investigated experimentally during the crystallization of solutions of ammonium bromide in a quasi-two-dimensional cell. Two regimes are observed. At small values of the Peclet number a self-affine fractal forms. In this regime it is known that the mean lateral front grows as t0.5. Here the length of each individual branch is shown to grow sbefore being screened offd with a power-law behavior tan. The value of the exponent ans0.5øanø1d is determined from the start by the strength of the initial disturbance. Coarsening then takes place, when the branches of small an are screened off by their neighbors. The corresponding decay of the growth of a weak branch is exponential and defined by its geometrical position relative to its dominant neighbors. These results show that the branch structure results from a deterministic growth of initially random disturbances. At large values of the Peclet number, the faster of the side branches escape and become independent dendrites. The global structure then covers a finite fraction of the two-dimensional space. The crossover between the two regimes and the spacing of these independent branches are characterized.
[ Back ]