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

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reproduce the measured temperature field. As pointed out earlier, the temper-
ature field remains mostly two-dimensional, and it is consequently easier to
reproduce than the three-dimensional flow field. Figures 7.108, 7.109, 7.116,
7.117 present comparisons between RSM-predicted and measured profiles of
the longitudinal and normal mean velocity within longitudinal planes and Fig-
ures 7.120 and 7.121 shows similar comparisons within the mid-plane parallel
to the two thermally active sides. The comparisons show that introduction of
the Basic RSM results in encouraging improvements in the flow field predic-
tions inside the stable 15 ◦ inclined cavity. In reasonable, though not complete,
agreement with the experimental data, within the central longitudinal plane,
Figure 7.108, the Basic RSM predicts a downward overall motion, while as
can be seen in Figures 7.116 and 7.117, towards the side-walls, again in ac-
cord with the measurements, the balance of the longitudinal flow direction
shifts towards the upward direction. This suggests that in agreement with the
measurements and in contrast to the k-ε predictions, the Basic RSM returns
a two-longitudinal-cell structure, with the fluid moving downwards within
the centre of the cavity and upwards along the two side walls. The predicted
profiles along the spanwise traverses, Figures 7.120 and 7.121, provide fur-
ther and indeed clearer confirmation. Figures 7.110, 7.111, 7.118, 7.119, 7.122
and 7.123 present the rms velocity profiles produced by the Basic RSM. The de-
tailed comparisons show that within the longitudinal planes, fluctuation levels
and the distribution are well predicted near the end walls, but over-estimated
towards the middle of the cavity. Within the mid-plane parallel to the ther-
mally active sides, Figure 7.122, differences between predicted and measured
velocity fluctuations are still substantial. Use of the RSM leads to closer agree-
ment between predicted and measured rms velocities than the deployment
of the k-ε, but overall agreement is not as satisfactory as for the mean flow
field. Apart from few of the sections which are over-predicted, RSM-Basic
improves not only the magnitude of rms velocities but also the shape of the
profiles. Figure 7.124 shows comparisons of the time-averaged longitudinal
distributions of the Nusselt number at four spanwise locations, Z=0.5, 0.625,
0.75, 0.865, predicted by the RSM-AWF, with the measured data. Unlike the
corresponding k-ε computations, the RSM predictions, show a monotonic rise
in Nusselt number in the longitudinal direction, which is in accord with the