A cylindrical Plexiglas cell of radius r0=6.35 cm and height d=12.7 cm is placed on a rotating table. An electric stepping motor drives the table with a rotational frequency w that can be varied from 0 to 2 Hz (maximum dimensionless rotation rate W~40,000). The top of the cell is covered with a thin (3 mm) sapphipe window. The upper surface of the window is in contact with water rapidly circulating through a Plexiglas cooler manifold connected to a water cooling/temperature control unit maintaining the temperature at a preset value with the accuracy of ±0.05 K. The bottom plate of the cell is made of anodized aluminium. An electric heater is attached to the lower surface of the bottom plate. Temperatures at the top and bottom of the cell are measured with thermistors and maintained at constant levels Tt=28.5 oC and Tb= 34 oC throughout the experiment. The Rayleigh number is R=2.7*108.
The light source used for visualization is a 300 W xenon arc lamp (5900 K). The light from the lamp is collimated with a cylindrical lens and passed through a slit, producing a narrow (2 to 4 mm) light sheet that can illuminate sections of the water-filled convection cell.