Development of a natural gas systems analysis model (GSAM)

This report provides an overview of the activities to date and schedule for future testing, validation, and authorized enhancements of Natural Gas Systems Analysis Model (GSAM). The goal of this report is to inform DOE managers of progress in model development and to provide a benchmark for ongoing and future research. Section II of the report provides a detailed discussion on the major GSAM development programs performed and completed during the period of performance, July 1, 1998 to September 30, 1999. Key improvements in the new GSAM version are summarized in Section III. Programmer's guides for GSAM main modules were produced to provide detailed descriptions of all major subroutines and main variables of the computer code. General logical flowcharts of the subroutines are also presented in the guides to provide overall picture of interactions between the subroutines. A standard structure of routine explanation is applied in every programmer's guide. The explanation is started with a brief description or main purpose of the routine, lists of input and output files read and created, and lists of invoked/child and calling/parent routines. In some of the guides, interactions between the routine itself and its parent and child routines are presented in the form of graphical flowchart. The explanation is then proceeded with step by step description of computer code in the subroutine where each step delegates a section of related code. Between steps, if a certain section of code needs further explanation, a Note is inserted with relevant explanation