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In this work, a comprehensive research study was carried out for the analysis of the underlying physical factors that control multiphase transport and flow dynamics in complex natural gas network topologies. The behavior associated with highly interlinked, closed-loop natural gas networks has been scrutinized in order to denude all fundamental relationships, critical links, and major parameters controlling performance in order to achieve the characterization of the most relevant transport features. The study included the formulation of proper governing equations coupled with thermodynamics, implementation of FVM schemes, and application to single-phase gas networks. The study concluded with the extension of the model to two-phase flow conditions and the preliminary analysis of the associated uneven split of phases at the T-junctions.

In the first year of work, the study of the proper formulation of governing equations was undertaken. The necessity of simultaneous solution of all the cells (control volumes) in a pipeline was emphasized from the stand point of network analysis and the foundation for multiphase flow studies was laid out. The importance of the finite volume method (FVM) in terms of conservative property and associated convenience of utilizing lesser number of cells have been shown for both single phase and two-phase analysis. Our studies showed that closed networks, involving several loops, could be modeled using the FVM model where junctions are replaced with tee structures. Utilization of the staggered grid approach, although poses some inconvenience in terms of boundary conditions, worked very well for the modeling of single phase flow at T-junctions in single phase conditions, allowing the FVM model to be easily extended for network solution without any special treatment.

In the final year of the work, the study focused on multiphase analysis in pipeline networks and on the uneven phase split problem at T-junctions. During this period, the two-phase flow FVM was tested for straight pipes with satisfactory results. In addition, the FVM model was extended to include the analysis of phase split at Tee-junctions. Satisfactory results were encountered for the case of isothermal flow of gas and water and validation was achieved using available experimental data. The proposed model has proven useful to analyze the preferential route of the water in the gas-water concurrent flow in natural gas pipe networks. Being able to predict this route enables network operators to map where liquid phases are found in the pipeline network and consequently identifying inefficiencies in the transportation system.

The ACS Type G Grant has provided the PI with critical resources at this early stage of his career to enable him to make steady and significant progress in his scholarship of research and enabled each member of his research group to maintain significant progress while working towards their academic goals. Along these lines, the graduate student assigned to this project, Doruk Alp, is scheduled to defend his doctoral thesis in Fall 2009. An underrepresented minority undergraduate student also took part of this project under an ACS-PRF SUMR award, bringing additional energy to the research group and making a very positive impact on our activities (progress report submitted separately). A portion of the main ACS-PRF award was also used to leverage additional funding for related two-phase split problems of interest to industry.