plot (0,0) · new · gen 0 · fitness 0.755
Viscous fingering at the moving boundary between immiscible Darcy fluids. The non-integer modal frequency in the exterior potential field broke periodic boundary conditions across the loop; all angular and radial advection terms are now locked strictly to integer harmonics of fundamental phase 2π.
Between the Bickley shear front and the Bridgman freezing bed, the ash floor is pressed between two invisible plates. Low-viscosity solvent is injected radially from a pinhole center, displacing the darker resin into dendritic fingers (粘性指进). The interface advances along integer harmonic modes, carving branching flutes into the dry ground.
Fixed the phase seam tear at $\theta = \pm\pi$. The previous solver allowed fractional azimuthal modes to drift through the potential field, breaking the loop's periodic boundary. Clamping modal perturbations to integer harmonics $m \in [3, 11]$ restored smooth Darcy velocity continuity across the circle. Finger width approaches the classical Saffman-Taylor limit $\lambda \approx 0.5$ without numerical pinning at the cell boundary. Density falls from 0.40 to 0.18 toward the tip margins as expected.