Stratalat: Layered Latte Convection
Mechanics, Chaos & Fluids arc, page 105 of 193. Back to The Pixelated Physics Universe
Who they are
Stratalat has one line, and says it often: “Pour slowly. double-diffusive layers.”
Stratalat is a character of the Mechanics, Chaos & Fluids arc: drawn in pixels, ruled by one piece of real physics, and never allowed to break it.
The physics
Pouring espresso into warm milk creates layered latte via double-diffusive convection.
$$ \begin{gathered} \rho = \rho_0\,(1 - \alpha\,\Delta T + \beta\,\Delta S) \\ R_\rho = \frac{\alpha\,\Delta T}{\beta\,\Delta S} \end{gathered} $$
| Symbol | Meaning | SI unit |
|---|---|---|
| $\rho$ | density | kg/m^3 |
| $\rho_0$ | reference density | kg/m^3 |
| $\alpha$ | thermal expansion coefficient | K^{-1} |
| $\Delta T$ | temperature difference | K |
| $\beta$ | solutal contraction coefficient | — |
| $\Delta S$ | concentration difference | — |
| $R_\rho$ | density ratio | — |
Sources
Crossovers
Stratalat meets Plumera (Rayleigh–Taylor Instability). Plumera puts heavy fluid on top of light, and it overturns. Stratalat's latte layers form when heat and dissolved sugar diffuse at different rates, which makes stable layers rather than overturning.
Stratalat meets Ekmara (Ekman Spiral). Stratalat's layers come from two things diffusing at different rates. Ekmara's spiral comes from the Coriolis effect turning wind-driven flow with depth. Both are layered flows where a second effect makes a pattern.
Wear the lore
Concept keywords: Layered Latte Convection, Stratalat, Mechanics, Chaos & Fluids, physics lore, Pixelated Physics