TOPAZ-SNLL, Transient 1-D Pipe Flow Analysis

1 - Description of program or function: TOPAZ-SNLL, the Transient One-dimensional Pipe flow Analyzer code, is a user-friendly computer program for modeling the heat transfer, fluid mechanics, and thermodynamics of multi-species gas transfer in arbitrary arrangements of pipes, valves, vessels, and flow branches. Although the flow conservation equations are assumed to be one-dimensional and transient, multidimensional features of internal fluid flow and heat transfer may be accounted for using the available quasi-steady flow correlations (e.g., Moody friction factor correlation and various form loss and heat transfer correlations). Users may also model the effects of moving system boundaries such as pistons, diaphragms, and bladders. The features of fully compressible flow are modeled, including the propagation of shocks and rarefaction waves, as well as the establishment of multiple choke points along the flow path. 2 - Method of solution: The flow conservation equations are discretized in space using conventional upwind finite differences. The spatially discretized gas flow equations together with the equations describing the motion of system boundaries constitute a set of mixed algebraic and ordinary differential equations. This equation set is solved implicitly using DASSL (NESC 9918), a differential-algebraic system solver. The DASSL software is included