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The NASA D-1.22-L boattail nozzle configuration was
obtained from the MADIC (Multidisciplinary and Design Industrial Consortium)
program. The geometry definition and the flow conditions are documented in NASA
TP 1766 [1]. This user tip presents a validation of numerical methods against
experimental data.
Geometry Definition
The model represents a cylinder with a sharp
conical front end, tapered blunt aft end and a convergent-divergent internal
nozzle. The geometry is discretized
using a structured mesh. A 2D axisymmetrical model is build in order to reduce
the CPU time requirements. The model contains 3 structured zones. On the solid
walls, a boundary layer mesh has been used. The total number of the cells is
around 16,600. The boattail nozzle mesh is presented in Figure 1.
Figure 1. 2D Axisymmetric Model
Numerical Results
The initial and boundary
conditions used for the NASA
D-1.22-L model are the following :
-
adiabatic walls on the solid boundaries,
-
symmetry on the axis of symmetry,
-
fixed static pressure exit condition,
-
inflow/outflow condition on other outermost surface
bounding the domain,
- fixed total pressure and
total temperature at the inlet at the nozzle.
| Rem |
306,000 |
|
| M (free stream) |
0.8 |
|
| T_total (free stream) |
592 |
deg. R |
| P_total (free stream) |
14.71 |
psia
|
| T_total (nozzle inlet) |
592 |
deg. R |
| P_total (nozzle inlet) |
14.47 |
psia |
| gamma |
1.4 |
|
The simulation is done using the structured solver
of CFD-FASTRAN. The Roe’s upwinding differencing scheme with min mod limitor is
used. Steady state solution is obtained using the Point Jacobi fully implicit
scheme. For the spatial discretization, high order numerical scheme is used. The
Menter SST k omega turbulence model has been used. On figure 2 we presented the
Mach number.
Figure 2. Mach number for NASA D-1.22-L model
The plot below compares the computational results
to the experimental data. The comparison is for pressure coefficient along the
aft external wall of the boattail nozzle.
Figure 3. Comparison Experiment (red)/CFD-FASTRAN (black)
We can note a good agreement between numerical
prediction and experimental measurements.
Regards,
Daniel Vinteler
CFD Support Manager - France
REFERENCES
[1] NASA TP 1766, Investigation of Convergent-Divergent Nozzles Applicable
to Reduced-Power Supersonic Cruise Aircraft, Bobby L. Berrier and Richard J.
Re, December 1980.
[2] www.grc.nasa.gov/WWW/wind/valid/madicnoz/madicnoz01/madicnoz01
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