Model Change Bulletin

                            MCB#5                 12/21/90

                   DEGADIS 2.1 (dated 90355)



     This Model Change Bulletin is to announce that a new version
of DEGADIS 2.1 has been installed on the SCRAM Bulletin Board. 
This version represents the culmination of several long-term
projects which have been independently funded by the American
Petroleum Institute, the Gas Research Institute, and the
Environmental Protection Agency.  The model package combines the
best features of each of these efforts to result in a unified
version of DEGADIS 2.1 which can be operated on either a personal
computer (IBM-PC or equivalent) or a VAX computer.  The model
development work was performed by the original DEGADIS authors, Tom
Spicer and Jerry Havens of the University of Arkansas.

     In addition to incorporating all of the features of the
previous VAX version, this version allows user interaction to
develop model inputs as well as batch model operation through the
use of previously-developed input files.  A few minor changes have
been made to the model in the past several months, mostly as a
result of feedback from SCRAM users.  These changes have generally
been associated with making the model more widely applicable, and
have not significantly changed the model predictions.  The current
version produces results which are numerically consistent between
the VAX and the PC (within computer roundoff), and which are
consistent with the previous VAX version.  

     Since this version operates in both VAX and IBM-PC computing
environments, it replaces completely the previous version of
DEGADIS 2.1 available on SCRAM.  The user's guide released by EPA
in early 1990 (NTIS PB90-213893) is still the official user's
guide, and supplemental information on installation and PC
operation is available in a text file named README.DOC which is
included in the modeling package.  In addition, documentation
will shortly be available through the American Petroleum Institute
detailing PC-specific features, and documentation is available
through the Gas Research Institute detailing the model's use in
simulating the dispersion of spills of liquefied natural gas.

      The DEGADIS 2.1 model code available from this bulletin board
is a FORTRAN source code intended for compilation and execution on
either a VAX computer using the VMS operating system or an IBM-PC
using the DOS operating system.

     After the source code programs have been dearchived, the file
README.DOC should be consulted for information concerning the
compilation of that code in the selected computing environment. 
Included with the source code are three example input files
(EX1.IN, EX2.IN and EX3.IN) and their associated output files
(EX1.OPT, EX2.OPT, and EX3.OPT), which may be used to test the code
after compilation.

      The source code for this model has been compiled and tested
on a VAX 8650 computer and on an IBM-PC using the Microsoft FORTRAN
compiler (math coprocessor optional).

     Watch SCRAM ALERTS for notification of new MCBs about DEGADIS
2.1.  

     All SCRAM users with an interest in dense gas dispersion
modeling are encouraged to download the new model package and give
it a trial run.  You should find it much more user-friendly than
the previous versions.  Problems, questions, or comments concerning
the new package of DEGADIS 2.1 may be referred to Dave Guinnup at
(919) 541-5368 or FTS 629-5368.