Pattern Formation

Gallery of Pattern Formation Experiments

Experiments performed at James V. Maher's lab in the University of Pittsburgh.

Click on the images below to see pattern formation movies. 

Radial Viscous fingering

Isotropic Viscous FingeringNitrogen gas is injected into mineral oil.
The dynamics is dominated by tip splitting of the growing fingers.







Anisotropic, Radial Viscous fingering

Anisotropic Radial Viscous FingeringNitrogen gas is injected into mineral oil. The lower plate of the cell has a rectangular etched lattice. 
Above a threshold injection rate , dendrites appear along one axis of the lattice.
Along the other axis, regular tip splitting persists.

Anisotropic Radial Viscous FingeringIncreasing the injection rate even further, dendrites appear along both axes of the rectangular array, but are still more prominent along one axis.


Viscous Fingering in Associating Polymers: from Viscous Fingering to Fracture

Radial geometry: Above a threshold injection rate, normal viscous fingering turns into fracture.
Side branches advancd far behind the tips, at large angles from the main branch.

ST FranctureChannel geometry: Above a threshold injection rate, the lower molecular weight associating polymer solutions display a sudden transition from Saffman-Taylor finger to fracture.

ST Oscillating FractureAbove a threshold injection rate, the highest molecular weight associating polymer solutions display a richer behavior.
The Saffman-Taylor finger becomes unstable in a less dramatic way, but turning into a meandering regime where the tip velocity oscillates with time.