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

Literature Review 54
and Cheesewright and King[17] carried out experimental investigations on
two-dimensional buoyant cavity flows. They studied rectangular cavities to
produce experimental data for validation of two-dimensional computer codes.
The working fluid was air and the Rayleigh number developed based on cav-
ity height was 10 10 . They produced a large amount of measurements of mean
and fluctuation values of velocity and temperature in the cavity. LDA and
thermocouples were employed to carry out the measurements of velocity and
temperature respectively. They observed that the flow on the hot and cold
walls were not symmetric to each other. They also reported re-laminarisation
on the floor wall and then transition to turbulence at 20% of the way up the
hot wall. The measurements of velocity fluctuations showed a reduction at
the bottom of the cavity, which reconfirmed the re-laminarisation phenomena
they reported here.
DafaAlla and Betts[18] experimentally studied turbulent natural convec-
tion in a tall air cavity. They analyzed turbulent natural convection in an air
cavity with an aspect ratio of 28.6. The experiment resulted in data for veloc-
ities and temperatures at a Rayleigh number based on cavity width of 0.83 ×
10 6 . The experimental data is useful for validating computational and theo-
retical studies. Velocity measurements were carried out by a Laser Doppler
Anemometer. Fine thermocouples were employed for temperature measure-
ments.
Betts and Bokhari[19] experimentally studied turbulent natural convection
in an enclosed tall cavity. The turbulent natural convection flow developed in
a tall differentially heated rectangular cavity (2.18 m high by 0.076 m wide by
0.52 m in depth). The temperature difference was imposed between the ver-
tical walls which were maintained at isothermal temperatures of 19.6 ◦ C and
39.9 ◦ C. This temperature difference resulted in a Rayleigh number of1.43×10 6
based on the width of the cavity as length scale. In the above mentioned situa-
tion, the flow in the core of the cavity was fully turbulent and variation of fluid
properties with temperature was negligible. They modified the experimental
rig previously used by Dafa ′ Alla and Betts[18] by fitting partially conducting
top and bottom walls and outer guard channels, to provide better adiabatic