Experimental Nusselt numbers for a cubical-cavity benchmark problem in natural convection

Experimental natural convection Nusselt numbers are reported for a cubical, air-filled cavity that has one pair of opposing faces isothermal at different temperatures, Th and Tc, the remaining faces having a linear variation from Tc to Th. Average Nusselt numbers at the cold face are given for Rayleigh numbers Ra equal to 104, 105, 106, 107 and 108, and for three angles of inclination φ of the isothermal faces from horizontal: namely φ = 0, 45 and 90°. The 95% confidence limits on the measured Nusselt number Nu are typically 1% of the Nu. Unexpectedly, two Nusselt numbers were found at φ = 0° and Ra = 105, depending on the initial conditions. The results are intended to provide data for a recently-defined benchmark problem in CFD.