Hele-Shaw cell
Related to Saffman-Taylor instability.
Apparatus for demonstrating and studying a pheonmenon known as viscous fingering (a.k.a. Saffman-Taylor instability), which is defined as "the formation of patterns in a morphologically unstable interface between two fluids in a porous medium" [1]. It occurs when a less viscous fluid is injected into a more viscous fluid, displacing it in a series of blobby, fractal-like fingers resembling (perhaps related to) the patterns formed by diffusion-limited aggregation or differential growth.
Setup:
The Hele-Shaw cell typically consists of two plates, usually glass or plexiglass, separated by a very short distance (TODO: how short?). A viscous fluid such as glycerin is injected through a hole either in the center of one of the plates or between the plates from the side, followed by colored water. As the colored water is injected and pressure is built up, the glycerin partially resists it's flow resulting in complex, wavy lines where the two liquids meet. For added effect, illuminate the cell by placing a light underneath, shining towards the viewer through the cell.
TODO: provide more details step-by-step instructions
TODO: note about lifted Hele-Shaw cells
Articles:
- Hele-Shaw flow on Wikipedia
Videos:
- Hele-Shaw cell experiments by Nervous System
- Hele Shaw Cell using ferrofluid and a magnet by manf1234
- Viscous Fingering in Multiport Hele Shaw Cell for Controlled Shaping of Fluids by Tanveer ul Islam and Prasanna S. Gandhi
Images:
- Schlieren Imaging of Viscous Fingering and Buoyancy Driven Convection by Simone Stewart