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

Inclined Cavity-2D simulations 168
that the Basic Reynolds stress model predicts the temperature distribution
quite well at the middle of the cavity. Its predictions deviate slightly from
the experimental measurements near the two ends of the cavity. The shape
of the temperature profile at the top of the cavity near the cold wall and at
the bottom of the cavity near the hot wall suggests that in these regions the
model over-predicts turbulence level compared to experimental data. Like-
wise in Figure 6.34, this turbulence over-prediction is increased by employing
the TCL Reynolds stress model. The turbulence over-prediction resulting from
the Reynolds stress models has already been observed in the vertical case [39],
but it seems that tilting the tall cavity augments the problem. Figures 6.35-
6.36 show shear stress distributions resulting from RSM-Basic and TCL com-
pared with k-ε-AWF. The comparisons show that RSM-Basic and TCL both
over-predict turbulent shear stress near the two ends of the cavity compared
with the k-ε-AWF prediction. This over-prediction becomes significant where
the RSM-TCL is employed. The overestimation of turbulence levels by the
RSM near the two end-walls, is consistent with the observed deviations be-
tween the measured thermal behaviour and that returned by the RSM.
Figure 6.37 shows the prediction of Nu number distribution along the cold
wall of the60 ◦ stable cavity resulting from RSM compared with the experimen-
tal data. The comparison shows there is a good match between RSM predic-
tions and experimental data. It also shows some improvements in Nu predic-
tions compared with k-ε-AWF (Figure 6.30). It may be due to more accurate
calculation of stresses and turbulent heat fluxes by RSM at the near-wall re-
gions.