Solution process for supersonic ramped-inlet

Supersonic ramped inlet problems are difficult to run. The incoming flow
is supersonic (Mach 2-3) and the fan face has a high pressure and the flow
is subsonic. It is difficult to specify good initial condition.

A two-step solution process has been developed:

1st Step (sample-2d-plugged.cas.gz, sample-2d-plugged.dat.gz)
- Use the segregated solver
- Load the case file
- Set the "ramp-out" zone to wall
- Set the incoming freestream boundary to be pressure-farfield
- Set the outgoing freestream boundary to be pressure-outlet
- Set the proper solution limits
- Initialize using the full freestream value
- Set the boundary for the fan face to wall and iterate until
first-order convergence is achieved (about 2000-3000 iterations)
At convergence, the average pressure at "ramp-out" is ~8.5atm
This means that the pressure at this boundary will be the maximum
pressure possible (p-max-outlet)
Thus, if this boundary is changed to pressure-outlet type and the
pressure value is set to p-max-outlet then there will be little
or no flow through this boundary
For flow to go out through this boundary, the pressure must be
lower than the p-max-outlet

2nd Step (sample-2d-final.cas.gz, sample-2d-final.dat.gz)
- Change the boundary type at fan-face to pressure-outlet
Use a pressure value that is slightly lower than p-max-outlet
Iterate for sufficient convergence
- Gradually lower the pressure value until the desired level is
achieved (i.e. 8.0atm)

Files for the sample problem can be found at:
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