Figure 1
From: Intensity of vortices: from soap bubbles to hurricanes
The bubble: (a) Set up: a brass disk (1) with a circular groove (3) can be rotated using a continuous motor (6) connected to it by a shaft (5). This disk is heated by the proximity of a hollow annulus (2) connected to a water circulation bath. The bubble is blown using the soap solution in the groove (3). The inner side of the brass disk is covered by a Teflon coating (2 mm thick) to minimize the heating of the air inside the bubble. The temperature at the equator of the bubble is set by the temperature of the water bath. (b) and (c) Images showing the detachment of thermal plumes from near the equator and rising towards the pole taken using an infrared camera (the temperature scale is in deg °C) (b) and a CCD color camera (c). (d) Image of the full bubble with a vortex being formed by a large thermal plume. (e) A zoom on the vortex, the colors are interference colors of white light being reflected by the thin water layer constituting the bubble. (f) Numerical simulation of thermal convection on the surface of a sphere of radius 1, the colors indicate the vorticity field. g) a zoom on the single vortex in image (f). The color code indicates the value of the vorticity and the grid used is 2048 × 2048.
