Flow visualization and heat transfer measurements have been made in the cavity between two corotating discs. The discs were 762 mm in diameter and could be rotated up to 2000 rpm. Air, at flow rates up to 0.1 kg/s, entered the cavity through either a central hole 76 mm in diameter or a porous inner shroud 380 mm in diameter; in both cases, the air left via holes in an outer shroud attached to the periphery of the discs. Flow visualization confirmed that Ekman-layer flow could occur: A source region, Ekman layers, sink layers, and interior core were observed. A simple theoretical model provided estimates of the size of the source region that were in satisfactory agreement with the observations. At sufficiently high rotational speeds, where Ekman layers form over much of the surface of each disc, measured Nusselt numbers were in reasonable agreement with values computed from the momentum-and energy-integral equations.

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