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**Hypersonic Diffuser**
# WIND Example Case: Hypersonic Cylinder

**
Figure 1. The grid, Mach surfaces, and pressure contours **

for a cylinder in hypersonic (Mach 15) airflow.

This example case involves a cylinder of radius 1.0 ft in a Mach 15
airflow with freestream static pressure and temperature of 3.0 psia
and 400 R, respectively. The grid density is 89 grid points along the
cylinder surface and 81 grid points from the surface to the freestream.
The grid spacing at the wall is 1.0E-05 ft. The PDT turbulence model
is used.

The computation was started from freestream conditions. To allow
for a stable start, Roe's first-order flux method was used along with
additional smoothing. The CFL number started out with a value of 0.05
for the first few hundred iterations. It was slowly increased to a
value of 0.5, which was the maximum stable CFL number that was allowed.
A total of 18800 iterations were ran and convergence was monitored by
observing the change in the boundary layer profile on the cylinder.
Table 1 reports the stagnation temperature on the cylinder.

Inflow / outflow boundary conditions were applied at the outflow
boundaries. This resulted in some strange behavior in the subsonic
portion of the boundary layer at the outflow boundaries. This can be
seen in the velocity vectors of Fig. 2 and Fig. 3. This was probably
due to the fact that the freestream pressure was being used for those
points, which is incorrect.

This case is still being worked on. Plans are to include chemistry
models for a more realistic simulation. The temperature of 17800 R is
well beyond the "onset" temperature of vibrational and dissociation
reactions and perhaps reaching ionization of the air molecules.

**
Figure 2. A plot of the velocity vectors.**

**
Figure 3. A plot of the velocity vectors.**

** Table 1. The data files and results. **
Description |
Input Data File |
Stagnation Temperature |

Calorically Perfect |
hc.C.dat |
17800 R |

Thermally Perfect |
- |
- |

Equilibrium |
- |
- |

Finite-Rate |
- |
- |

## Questions / Comments

Questions or comments about this case can be sent be emailed John W. Slater at the
NASA Lewis Research Center.

Last Updated: Thursday, 17-Jul-2008 07:01:16 EDT