Page 358 - Computational Fluid Dynamics for Engineers

348 11. Incompressible Navier-Stokes Equations

5.0 -0.3-
• Exp
BB
4.5 SA
-0.4- SST
DM
4.01 c m *
« » • •
-0.5-
•
3.51

-0.6-
3.0
*j/
2.5 -i r- _n 7- 1 —i — i —i— i 1 1 '
4 8 12 16 20 24 12 16 20 24
a a
(a) (b)
6
Fig. 11.11. Results for geometry B at Re = 9 x 10 , variation of (a) ci and (b) c m with

5.0-

• Exp
4.5" BB / >
SA •
SST
DM •
4.0H /yvv*
c
l
ifmi'f
y.5- • if ft
i' •
» m
3.0"

0.00 0.02 0.04 0.06 0.08 0.1 Fig. 11.12. Drag polar for geometry
C 6
d B a t R e = 9 x l 0 .

The computing time utilized by INS2D varies somewhat from one turbulence
model to the other. The BB and SA models have a single differential equation
whereas the SST and DM have two differential equations. The SST model con-
verges best when 10 line-relaxation sweeps are used during one iteration, the
others work best when only 2 sweeps are used. Thus the SST model takes more
time per iteration. Figure 11.13 shows the maximum residual of the mean flow
equations versus iteration number for geometry A at 21°. There are numerous
oscillations occurring in the residual. These are due to the behavior at the zonal