Published online by Cambridge University Press: 21 April 2006
The fluid flow types observed in a new rotating cylindrical annulus configuration are presented in regime diagrams. This new annulus has radial temperature gradients imposed on plane, horizontal, thermally conducting endwalls and the cylindrical sidewalls are insulators. This configuration is to be contrasted with the classical cylindrical annulus which has differentially heated conducting sidewalls and insulating endwalls. Studies of the flows occurring in the classical annulus have contributed much to our understanding of basic atmospheric dynamics. Unlike the classical annulus the new configuration permits a measure of control over the internal vertical temperature gradient. To observe the flow from above (and below) and to satisfy the conduction requirement, transparent sapphire disks are used for the endwalls. The fluid used was water. Qualitative observations of the flow types were made using a small amount of rheoscopic concentrate added to the water.
As well as the axisymmetric flow and non-axisymmetric baroclinic wave flow which occur in the classical annulus, two additional non-axisymmetric flow types, boundary-layer thermal convection and deep thermal convection, are observed in the new annulus. Three flow regime diagrams for three different values of the imposed vertical temperature difference are presented. The flows are described and explanations for the flow transitions are offered.
It is argued that the new annulus configuration is more relevant to real atmospheric flows than the original annulus. Another motivation for this research was to provide scientific backup for the Atmospheric General Circulation Experiment (AGCE). The AGCE is a true spherical baroclinic flow experiment which can only be realized in a low gravity environment and which has been proposed for space flight.
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