AIPP- ATMOSPHERIC INTERACTION PLUME PROGRAM

( AEROCHEM RESEARCH LABS., INC. )

     This computer program can be used to predict the gas dynamic and chem-
ical properties of underexpanded rocket plumes from sea level to the al-
titude above which the viscous continuum flow assumption, with distinct
shocks, is no longer valid. The program computes the plume shock struc-
ture while simultaneously accounting for turbulent mixing, nonequilibrium
chemistry, and gas/particle nonequilibrium effects. The program also has
the ability to calculate plume properties in the subsonic region downstream
from the Mach disc, downstream of the shock reflected from the triple point,
and in the far field. The program can readily be used to determine plume op-
tical and electrical properties, which are necessary data for calculat-
ing the infrared radiation pattern and radar cross section. This program
was used to calculate deposition rate of various nitrogen oxides into the
stratosphere caused by the Space Shuttle exhaust plumes.

     The AIPP code is based on the Multitube code developed by Boyton (which
incorporates the finite difference streamtube calculation technique) and
has been expanded to treat particle/gas nonequilibrium, chemical kinetic,
and turbulent mixing effects within exhaust plumes. For the gas flow up-
stream of the Mach disc, the governing elliptic Navier-Stokes equations
are reduced to a hyperbolic system (including lateral pressure gradients)
by neglecting diffusion of mass, momentum, and energy along streamlines as
compared with that across streamlines. The conservation equations are then
written in a streamline oriented coordinated system. Shocks are treated as
thin bounding surfaces of the flow across which the Rankine-Hugoniot rela-
tions are applicable. In the subsonic region behind the Mach disc the in-
viscid flow governing equations are taken to be elliptic. The equations of
flow must be solved within the supersonic and subsonic regions, while si-
multaneously maintaining the equality of pressure and flow direction along
the dividing streamline. In meeting these boundary conditions several ap-
proximations are employed to reduce the amount of computer time and storage
required. For the condensed phases present within the flow a continuum par-
ticle cloud assumption is made and field conservation equations for conti-
nuity, momentum, and energy can be written for the particles.

     A finite difference formulation of the gas phase and particle cloud
governing equations is utilized on a grid which lies along and perpen-
dicular to the streamlines. The gas flow equations are solved via an ex-
plicit finite difference marching technique. The chemical production
terms utilize an implicit finite difference formulation because an ex-
plicit formulation leads to an impractically small integration step for
near-equilibrium chemistry. The particle equations have no wave or diffu-
sive nature and are solved explicitly via a finite difference formulation.
Initially, all flow properties, streamline positions, and angles must be
known along an orthogonal surface. The streamlines are extended an incre-
mental distance forming a streamtube. The properties at the upstream sur-
face are used, along with the governing equations, to determine all the nec-
essary properties at the downstream surface. Below the Mach disc a similar
procedure using assumed streamlines is performed.



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     The computer program is written so that only minimal judgment by the
user is required to operate it. The input data required are nozzle exit con-
ditions along a surface orthogonal to the exit streamlines, uniform su-
personic external flow conditions, and a suitable reaction mechanism and
rate coefficients. The output contains the results of all calculations in
a highly readable format. Care must be taken that the program is not used to
predict plume characteristics at altitudes above which the assumption of
continuum flow ahead of the Mach disc starts to break down.

     This program is written in FORTRAN IV to operate in the batch mode and
has been implemented on a CDC CYBER 175 with a central memory requirement of
approximately 40K 60 bit words.

     COSMIC, and the COSMIC logo are registered trademarks of the National
Aeronautics and Space Administration. All other brands and product names
are the trademarks of their respective holders.



LANGUAGE: FORTRAN IV

MACHINE REQUIREMENTS: CDC CYBER 70 SERIES

PROGRAM SIZE: APPROXIMATELY 5,950 SOURCE STATEMENTS

DISTRIBUTION MEDIA: 9 Track 1600 BPI CDC NOS Internal Format Magnetic Tape

PROGRAM NUMBER: LAR-12203

DOMESTIC - DOCUMENTATION PRICE: $27.00    PROGRAM PRICE: $500.00

INTERNATIONAL - DOCUMENTATION PRICE: $54.00   PROGRAM PRICE: $1000.00



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