Recent improvements in the SINDA/FLUINT computer program have made the program into a highly capable, commercially viable software product for general mathematical modeling of thermohydraulic systems. Versions of SINDA/FLUINT have been described in a number of previous NASA Tech Briefs articles. To recapitulate: SINDA/FLUINT is the NASA standard software system for computational simulation of interacting thermal and fluid effects in arbitrary flow networks. As its name suggests, SINDA/FLUINT is an integral combination of two subprograms: Systems Improved Numerical Differencing Analyzer (SINDA) program is a software system for solving lumped-parameter representations of physical problems governed by diffusion-type equations. The Fluid Integrator (FLUINT) program is an advanced one-dimensional fluid-analysis program that solves equations of arbitrary fluid-flow networks. Working fluids that can be modeled in SINDA/FLUINT include single-phase vapors, single-phase liquids, and two-phase fluids.

The recent improvements in SINDA/FLUINT fall into two categories. In the first category is the addition of capabilities for advanced mathematical modeling of two-phase flows of types that are of particular relevance to thermal-control, propulsion, environmental-control, and fire-suppressant-delivery systems. Phenomena that could not previously be modeled but can now be modeled include the dissolution and evolution of noncondensable gases and the effects of thermal equilibrium between the liquid phase and the vapor/gas phase in a pipe. Specific features added to the program include one that defines the equilibrium dissolution of a solvent/solute pair, mass-transfer correlations based on flow regime, a feature for tracking of solutes and rates of evolution and dissolution in both tank and junction network elements, interface network elements to provide for subdivision of control volumes, twinned tanks, twinned ties, and superpaths.

The second category of improvements comprises miscellaneous additions that provide enhanced capabilities for posing and solving problems. The additions include (1) prepackaged software components that provide options for handling ducts with axially varying flow areas, (2) software components that provide double-precision solution options, (3) software components that implement some optional solution techniques, and (4) a database subprogram that manages complex relationships among inputs and outputs and represents these relationships in a spreadsheet. The latter improvement relieves the user of some programming tasks, making parametric analyses easy and making the program easier to learn and to apply to complex problems.

This program was written by Brent Cullimore, David A. Johnson, and Steven G. Ring of Cullimore and Ring Technologies, Inc., for Johnson Space Center. For further information, access the Technical Support Package (TSP) free on-line at  under the Software category.


NASA Tech Briefs Magazine

This article first appeared in the October, 2001 issue of NASA Tech Briefs Magazine.

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