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

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Rayleigh number Ra = βg∆ΘL3
να = 0.8 × 106 (Cooper et al. [8]) for the 60 ◦ stable
and unstable, and the 15 ◦ stable and unstable configurations. The hot and
cold wall temperatures are 34 ◦ C and 16 ◦ C respectively. These uniform wall
temperatures are produced by imposing heat flux to the corresponding walls.
The fluid inside the tall cavity is air. The height of the cavity, H, is 2.18m and
its width, L, is 0.076m. The spanwise dimension of the cavity used in the ex-
periment was 0.52m. Comparisons with the experimental traverses (between
the hot and cold sides) of [8] have been made along 4 different cross sections,
which are shown in Figure 6.5. The Nusselt numbers are also compared with
available experimental data along the hot and cold walls. The local Nusselt
numbers are calculated asNu = −L(∂Θ/∂xi) w /(Θh −Θc), whereLis the dis-
tance between the hot and the cold walls. The velocity scale is defined as
V0 = √ gβL∆Θ, whenβ is the volumetric expansion factor and∆Θ = Θh−Θc.
y
x
H
Y=0.1
Adiabatic
Hot Wall
Y=0.5
Ψ
Y=0.7
Cold Wall
Y=0.95
L
Adiabatic
Figure 6.5 – Schematic of inclined tall cavity and its thermal boundary condition.
Figure 6.6 shows the experimental data of wall-parallel velocity and rms
velocity fluctuations in the 60 ◦ stable inclined cavity. It shows the velocities
at the mid-height (y/H=0.5) and near the two ends of the cavity (y/H=0.1
and 0.95). At each longitudinal section, the profiles at the centreline in the
spanwise direction (z/D=0) are compared with the measured velocities off the
centreline (z/D=0.25). The experimental data reported that in this cavity, as