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.

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.