The computation of turbulent natural convection flows - Turbulence ...

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Cavities and Enclosures
Kirkpatrick and Bohn[4] experimentally studied natural convection at a
high Rayleigh number in a cubical enclosure with various thermal boundary
conditions. They ran experiments using four different configurations of differ-
entially heated and cooled vertical and horizontal walls. They made measure-
ments of mean and fluctuating values of temperature and observed fluid flow
patterns in the enclosure. It was concluded that heating from below would
cause more mixing in the enclosure and consequently cause a reduction of
temperature stratification. As the Rayleigh number was increased, the ther-
mal stratification at the core of the cavity decreased. They observed that the
thermal stratification changed suddenly atRa ≈ 0.65×10 10 . The thermal strat-
ification was also not symmetric around the mid-plane. Increasing the bottom
wall temperature, which increases the Ra number, lead to an increase of the
temperature difference between the bottom wall and the core and produces
stronger thermal plumes which in turn caused greater mixing of the core. The
range of Rayleigh numbers covered in the experiment was from 0.1 × 10 10 to
3×10 10 . The working fluid was water. Comparisons were made between av-
erage Nusselt numbers over the bottom wall of the cavity at various thermal
boundary conditions from the experiment and some available correlations of
Nusselt and Rayleigh number (such as Figure 2.5). This Figure corresponds to
the thermal boundary condition in which the bottom wall is hot and the top
wall is cold and the side walls are adiabatic. The experimental measurements
show that the averaged Nu number has a 1/3 power dependence on the Ra
number.
Figure 2.5 – Heat transfer data and correlations for the Rayleigh-Bénard
configuration[4].
Cheesewright et al.[14], Cheesewright and Ziai[15], Bowles and Cheesewright[16]