scholarly journals Induced side-branching in smooth and faceted dendrites: theory and phase-field simulations

2022 ◽  
Vol 380 (2217) ◽  
Author(s):  
Gilles Demange ◽  
Renaud Patte ◽  
Helena Zapolsky
Keyword(s):  
Steady State ◽  
Surface Energy ◽  
Complex Systems ◽  
Phase Field ◽  
Interface Velocity ◽  
Interface Temperature ◽  
Theme Issue ◽  
Trade Off ◽  
Normal Angle ◽  
Temperature Surface

The present work is devoted to the phenomenon of induced side branching stemming from the disruption of free dendrite growth. We postulate that the secondary branching instability can be triggered by the departure of the morphology of the dendrite from its steady state shape. Thence, the instability results from the thermodynamic trade-off between non monotonic variations of interface temperature, surface energy, kinetic anisotropy and interface velocity within the Gibbs–Thomson equation. For the purposes of illustration, the toy model of capillary anisotropy modulation is prospected both analytically and numerically by means of phase-field simulations. It is evidenced that side branching can befall both smooth and faceted dendrites, at a normal angle from the front tip which is specific to the nature of the capillary anisotropy shift applied. This article is part of the theme issue ‘Transport phenomena in complex systems (part 2)’.

scholarly journals Interface Velocity Transients During Melting of a-Si/C-Si Thin Films

1988 ◽  
Vol 100 ◽  
Author(s):  
J. Y. Tsao ◽  
M. J. Aziz ◽  
P. S. Peercy ◽  
M. O. Thompson
Keyword(s):  
Thin Films ◽  
Steady State ◽  
Pulsed Laser ◽  
Interface Velocity ◽  
Interface Temperature ◽  
Laser Melting ◽  
Systematic Procedure ◽  
Solid Interface ◽  
Amorphous Si ◽  
Si Films

ABSTRACTWe report transient conductance measurements of liquid/solid interface velocities during pulsed laser melting of amorphous Si (a-Si) films on crystalline Si (c-Si), and a more accurate, systematic procedure for analyzing these measurements than described in previous work [1]. From these analyses are extracted relations between the melting velocities of a-Si and c-Si at a given interface temperature, and between the temperatures during steady-state melting of a-Si and c-Si at a given interface velocity.

The shape of dendritic tips: a test of theory with computations and experiments

2021 ◽  
Vol 379 (2205) ◽  
pp. 20200326 ◽  
Author(s):  
Dmitri V. Alexandrov ◽  
Liubov V. Toropova ◽  
Ekaterina A. Titova ◽  
Andrew Kao ◽  
Gilles Demange ◽  
...  
Keyword(s):  
Experimental Data ◽  
Complex Systems ◽  
Phase Field ◽  
Shape Function ◽  
Supercooled Liquid ◽  
Detailed Comparison ◽  
Research Groups ◽  
Computational Simulations ◽  
Theme Issue ◽  
Comparison With Experimental Data

This article is devoted to the study of the tip shape of dendritic crystals grown from a supercooled liquid. The recently developed theory (Alexandrov & Galenko 2020 Phil. Trans. R. Soc. A 378 , 20190243. ( doi:10.1098/rsta.2019.0243 )), which defines the shape function of dendrites, was tested against computational simulations and experimental data. For a detailed comparison, we performed calculations using two computational methods (phase-field and enthalpy-based methods), and also made a comparison with experimental data from various research groups. As a result, it is shown that the recently found shape function describes the tip region of dendritic crystals (at the crystal vertex and some distance from it) well. This article is part of the theme issue ‘Transport phenomena in complex systems (part 1)’.

Numerical Solution of Alloy Solidification and Columnar Eutectic Growth Using a Phase-Field Model

2001 ◽  
Author(s):  
Ward Judson ◽  
Samuel Paolucci
Keyword(s):  
Phase Field ◽  
Transfer Problem ◽  
Eutectic Growth ◽  
Freezing Temperature ◽  
Phase Field Method ◽  
Interface Temperature ◽  
Temperature Phase ◽  
Alloy Solidification ◽  
Interface Position ◽  
Solid Liquid

Abstract Near-eutectic alloys freeze with a macroscopically discrete solid-liquid interface at a temperature below the equilibrium eutectic temperature. The velocity dependence of the freezing temperature results from the microscale species diffusion for microstructures with coupled eutectic growth characteristic of a near-eutectic alloy composition. At solidification rates that are representative of gravity permanent mold and die casting processes, consideration of the nonequilibrium conditions at the interface affects the prediction of the macroscale thermal field, and it in turn affects microscale properties. A phase-field formulation is presented to model the alloy solidification which implicitly links the interface temperature to the interface speed. The utility of the method is well-suited for complex evolving solid-liquid interfaces and the velocity-dependent freezing temperature is satisfied implicitly. The dimensionless governing equations are solved numerically with a fixed-grid Galerkin finite element method. After demonstrating sufficient numerical accuracy, temperature, phase field, and interface position results are presented for a square domain and three-dimensional casting geometry. Limitations of the phase-field method are discussed, and the conjugate heat transfer problem is studied to address boundary condition issues.

scholarly journals The sleeping brain as a complex system

2011 ◽  
Vol 369 (1952) ◽  
pp. 3697-3707 ◽  
Author(s):  
Eckehard Olbrich ◽  
Peter Achermann ◽  
Thomas Wennekers
Keyword(s):  
Complex Systems ◽  
Complex Networks ◽  
Systems Approach ◽  
Complex Dynamics ◽  
Activity Patterns ◽  
Complexity Science ◽  
Sleep Stages ◽  
Sleep Regulation ◽  
Theme Issue ◽  
The Brain

‘Complexity science’ is a rapidly developing research direction with applications in a multitude of fields that study complex systems consisting of a number of nonlinear elements with interesting dynamics and mutual interactions. This Theme Issue ‘The complexity of sleep’ aims at fostering the application of complexity science to sleep research, because the brain in its different sleep stages adopts different global states that express distinct activity patterns in large and complex networks of neural circuits. This introduction discusses the contributions collected in the present Theme Issue. We highlight the potential and challenges of a complex systems approach to develop an understanding of the brain in general and the sleeping brain in particular. Basically, we focus on two topics: the complex networks approach to understand the changes in the functional connectivity of the brain during sleep, and the complex dynamics of sleep, including sleep regulation. We hope that this Theme Issue will stimulate and intensify the interdisciplinary communication to advance our understanding of the complex dynamics of the brain that underlies sleep and consciousness.

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