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Figure 2. Principle of the large-scale isothermal LARA experiment. 18
side, with a primary flow of ‘hot gases’; the second one, denoted by ‘2’, represents the casing,
with a secondary flow of ‘cooling air’ (Fig. 2). The two channels (height h = 120mm and
width l = 400mm) are separated by a plate perforated with holes of diameter d = 5mm
(0.5mm is the common value for gas turbines). Twelve rows of staggered holes are drilled into
the plate that separates the two channels. A grid is placed at the outlet section of channel 2
in order to generate a pressure drop across the plate. Because the pressure is higher in the
‘casing side’, a fraction of the air flowing in channel 2 is injected through the perforated plate.
The spacing between the holes corresponds to classical industrial applications: the distance
between two rows of holes is 5.84 diameters in the streamwise direction and 3.37 diameters in
the spanwise direction. Due to the staggered disposition of the perforations, the hole-to-hole
distances are 2 × 5.84 and 2 × 3.37 diameters in the streamwise and spanwise directions
respectively. The thickness of the plate being e = 10mm and holes being angled at α = 30 ◦
with the plate, the hole length-to-diameter ratio is 4. Note that the perforations are only
angled in the direction of the main flow, without any spanwise component. Measurements
are performed at ambient temperature.
The LARA database has been used twice: first, the LES presented in section III deals
with the same geometry as the LARA test rig. Numerical and experimental results are
compared in Mendez et al. 30 Then, in section IV, a model for discrete effusion through a
plate is implemented in our CFD code. The validation case is also the LARA experiment.
One operating point has been considered: the pressure drop across the plate is ∆P = 42 Pa.
The Reynolds number for the primary ‘hot’ flow (based on the duct centerline velocity U 1
and the half height of the rectangular duct h/2) is Re 1 = 17750, while it is Re 2 = 8900 for the
secondary ‘cold’ flow. The characteristics are given upstream of the perforated zone, where
the flow is fully-developed. The Reynolds number in the hole, based on the momentum in
the jet core et the hole exit and the hole diameter is Re h = 2600. The ninth row has been
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