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11th World Congress on Computational Mechanics (WCCM XI)5th European Conference on Computational Mechanics (ECCM V)
6th European Conference on Computational Fluid Dynamics (ECFD VI)
July 20–25, 2014, Barcelona, Spain
COMPREHENDING THE MECHANISM OF VEINFORMATION - INSIGHTS FROM THREE-DIMENSIONAL
PHASE-FIELD MODELING AND INNOVATIVEPOST-PROCESSING TECHNIQUES
Kumar Ankit1,∗, Michael Selzer2 and Britta Nestler1
1 IMP, Karlsruhe University of Applied Sciences and IAM, Karlsruhe Institute of Technology,Haid-und-Neu Str. 7, 76131 Karlsruhe,
[email protected], [email protected] IAM, Karlsruhe Institute of Technology, Haid-und-Neu Str. 7, 76131 Karlsruhe,
Key words: Phase-field method, Geological veins, Crack-sealing microstructure, Numer-ical post-processing
Vein formation in earth’s crust involves a complex interplay of material transport and lo-cal precipitation during ongoing deformation. The geological experts try to correlate thedifferent indicators which may vary across length scales, to reconstruct the past events,in order to gain an understanding of vein formation. However, it is difficult to decomposethe effect of different processes that might have acted in sequence or simultaneously insuch studies. The approximate reconstruction, which determines the final vein morphol-ogy could often be misleading and may result in erroneous interpretation of evolutionmechanism. On the contrary, numerical methods applied to the study of vein microstruc-ture formation improves the general understanding, as it is possible to decompose theeffect of various boundary conditions. Further, computations provide an in-situ look intothe temporal evolution of grains. In spite of numerous attempts in the past to simulatethe dynamics of vein growth process, numerical studies are limited to two dimensions. Itis to be noted that the grain formation process is generically of 3-D nature and can beinterpreted in a physically sufficient manner by methods capable of capturing the growthcharacteristics and dynamics in full 3-D space.
In the present work, we extend the previous numerical studies [1] and primarily focuson the three-dimensional phase-field study of crystal growth in veins under crack-sealingconditions. Fig. 1 illustrates the successive steps of the simulation work-flow, startingfrom an initial wall crack surface/voronoi structure up to the various microstructuralcharacterization methods. By the aid of innovative post-processing and advanced visual-ization techniques, the major advantages of accounting for the third dimensionality arehighlighted. The grain growth statistics obtained from simulation studies provide valu-
Kumar Ankit, Michael Selzer and Britta Nestler
Normal opening Shear openingParent crystal
after 1st cracking
after 3rd cracking
after 4th cracking
after 2nd cracking
plotted with offset plotted without offset
Generate ‘realistic’ boundary condition algorithmically (fractal surface)
Pre-
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essi
ng
Adv
anci
ng
wal
l roc
k Visualisation
Initial condition
Statistics
0
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0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4
Fre
quency
Normalized grain size R/R0
Simulation A (slow opening rate) Number of grains = 188
Simulation B (fast opening rate) Number of grains = 86
0
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0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Nu
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Normalized distance from nucleation surface
constant
decreasing
Slow opening (Simulation A)Fast opening (Simulation B)
Post-processing
Masking fractal peaks Grain barycenter evolution in moving box simulation
Grain size distribution Grain count versus time
Rep
eate
d cr
ack-
seal
ing
Vis
ualis
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phol
ogie
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Voronoi (initial condition)
Non-fragmented Evolution of crystal fragments
Phase-field simulation of crack-sealing process
Figure 1: A general work-flow adopted for three-dimensional phase-field simulation of the crack-sealingprocess in geological veins under different boundary conditions.
able insights into the evolution characteristics; no such information is usually accessiblein field studies and is essentially difficult to obtain from laboratory experiments as well.We also propose a general framework based on multiphase-field modeling [2], which allowsan efficient use of modern high super-computing power, so that even the consideration oflarge grain systems (up to 500,000 grains) in 3-D computational studies becomes feasible.
REFERENCES
[1] K. Ankit, B. Nestler, M. Selzer, M. Reichardt. Phase-field study of grain boundarytracking behavior in crack-seal microstructures. Contrib. Mineral Petr., Vol. 166,1709–1723, 2013.
[2] B. Nestler, H. Garcke, B. Stinner. Multicomponent alloy solidification: Phase-fieldmodeling and simulations. Phys. Rev. E, Vol. 71, 041609, 2005.
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