these simulation numerique et modelisation de l'ecoulement autour ...

LES of a bi-periodic turbulent flow with effusion 11
12
10
a
12
10
b
8
8
y/d
6
4
y/d
6
4
2
2
0
0
0.0
0.4
0.8
1.2
0.0
0.4
0.8
1.2
12
10
< U > /V j
c
12
10
< U > /V j
d
8
8
y/d
6
4
y/d
6
4
2
2
0
0
0.0
0.4
0.8
1.2
< U > /V j
< U > /V j
Figure 4. Time-averaged streamwise velocity profiles at four locations: comparison between
experimental results ( • ), Run A ( ), Run B ( ) and Run C ( ). Graphs
correspond to the locations (a), (b), (c) and (d) presented in figure 9.
0.0
0.4
0.8
1.2
12
10
a
12
10
b
8
8
y/d
6
4
y/d
6
4
2
2
0
0
0.00
0.10
0.20
0.30
0.00
0.05
0.10
0.15
0.20
0.25
12
10
< V > /V j
c
12
10
< V > /V j
d
8
8
y/d
6
4
y/d
6
4
2
2
0
0
0.00
0.05
0.10 0.15 0.20
u rms/V j
0.25
0.00
0.05 0.10 0.15
v rms/V j
Figure 5. Velocity profiles: comparison between experimental results ( • ), Run A ( ), Run
B ( ) and Run C ( ). (a): time-averaged vertical velocity at station (c), x = 2.92 d,
(b): time-averaged vertical velocity at station (d), x = 5.84 d, (c): streamwise RMS velocity at
station (c), x = 2.92 d, (d): vertical RMS velocity at station (c), x = 2.92 d.
0.20
grid results (Run A). Further downstream (figure 4d), the jet looses its strength and
progressively mixes with the film. Also, the velocity near the wall increases compared
to figure 4(c); this is an effect of the entrainment process (see for example Yavuzkurt
et al. 1980a): when the blowing ratio is high enough (typically greater than 0.5), the
jets separate and penetrate deeply in the boundary layer. The main flow bypasses the
jet and experiments a movement towards the plate, resulting in negative values of wallnormal
velocity around the jet (see § 4.4 and 4.5). An effect of the entrainment process
is to reattach the main flow downstream of the jet, inducing the increase in streamwise
velocity observed in figure 4(d).
Regarding the potential effect of the number of holes included in the bi-periodic do-