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Convection Cell

What it Shows

Hot fluid rises, cool fluid sinks. Here is a desktop convection cell modeling the processes in the atmosphere, oceans or stellar interiors.

Convection Cell in the Prep Room, narrated by Steve Wofsy: https://youtu.be/22zVmRYOW10
See also: Geophysics

How it Works

The currents are set up in rheoscopic fluid[1] (basically minute aluminum flakes in water) in a small 10×10×15cm glass tank. Half the base of the tank rests on a heater, the other on an aluminum block that acts as a heat sink. The rheoscopic fluid has a weird metallic sheen such that the bulk motion of fluid is clearly seen from the changing reflectivity.

Schematic diagram of convection cell in action
Schematic diagram of the flow in different parts of the apparatus.

Setting it Up

The heater is a small hotplate set at around 200W output. The aluminum block needs to be chosen to match the height of the heater (or adjusted to do so) for good thermal contact. The translucent nature of the fluid makes back lighting probably the best option—there is too much reflection off of the glass wall in front lighting. A camera setup is required—play around with the aperture to get the best contrast.

Schematic diagram of the direction of fluid flow in the tank.
The fluid can be seen rising up above the heater and sinking down in the cooler region.

Comments

This presentation of convection currents is a preferred choice to the Thymol Blue Cell.

[1] made by Kalliroscope Inc., 111 Pine Street Graham NC 27253

See also: Geophysics, The Atmosphere, Thermal Physics, Conduction, Convection, and Radiation, [S], [M], [t+], [★★★]