Saffman-Taylor instability: less viscous fluid displaces more viscous fluid
In a Hele-Shaw cell (two closely-spaced plates), injected fluid forms fractal fingers via the Saffman-Taylor
instability. Surface tension stabilizes small wavelengths; viscosity contrast drives instability.
With crystallographic anisotropy (set Anisotropy > 0), fingers align along preferred axes producing
dendrite-like patterns. Simulated via diffusion-limited aggregation (DLA) on a grid.