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

199
Nu
60
40
20
LES
AWF
LRN
SWF
0
0 0.2 0.4 0.6 0.8 1
Y
Figure 6.67 – Local Nusselt numbers along hot wall within 5◦ stable tilted tall
cavity.
6.7 Closing remarks
In this Chapter, three different test cases have been numerically investi-
gated regarding turbulent natural convection. The test cases were selected so
that they cover various physical phenomena such as single and multiple cell
circulation and stable and unstable stratified flow. The comparisons in this
Chapter showed that the k-ε model using the AWF near-wall strategy pro-
duces reliably accurate predictions for the 5 ◦ stable, 60 ◦ stable and 60 ◦ unsta-
ble. Introduction of the RSM models over-estimates turbulent kinetic energy
near the top and the bottom of tall cavity in the 60 ◦ stable inclined case. The
over-prediction is significant in the case of the RSM-TCL using AWF. The in-
troduction of the θ 2 and εθ transport equations, with more complex algebraic
thermal flux models improves the RSM-basic and TCL predictions near the
top and the bottom of the tall cavity. The improvement is more significant
in RSM-θ 2 -εθ-TCL case. In the 60 ◦ stable case these extended stress transport
models then produce better predictions than the corresponding eddy viscosity
schemes.