NASA Technical Reports Server (NTRS) 20100014077: Software for Automated Generation of Cartesian Meshes

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by  NASA Technical Reports Server (NTRS)

Software
An object-oriented design was used to access memory available for other com-
Computing Isentropic satisfy additional requirements and to putations.
Flow Properties of Air/ make the software easily extendable. By These programs were written by Joseph
R-134a Mixtures virtue of its platform independence, Gonzalez, Robert Chamberlain, Eric Tailor,
MACHRK is a computer program JMEWS can be used on the UNIX work- and Gary Gutt of Caltech for NASA’s Jet
that calculates isentropic flow proper- stations in the Mission Control Center Propulsion Laboratory. Further informa-
ties of mixtures of air and refrigerant (MCC) and on office computers. tion is contained in a TSP (see page 1).
R-134a (tetrafluoroethane), which are JMEWS includes an interactive editor This software is available for commercial
used in transonic aerodynamic testing that allows users to easily develop dis- licensing. Please contact Karina Edmonds of
in a wind tunnel at Langley Research plays that meet their specific needs. The the California Institute of Technology at
Center. Given the total temperature, displays can be developed and modified [phone]. Refer to NPO-40596.
total pressure, static pressure, and while viewing data. By simply selecting a
mole fraction of R-134a in a mixture, data source, the user can view real-time,
MACHRK calculates the Mach number recorded, or test data. Software for Automated
and the following associated flow prop- This program was written by Ross Pet- Generation of Cartesian
erties: dynamic pressure, velocity, den- tinger, Tim Watlington, Richard Ryley, and Meshes
sity, static temperature, speed of sound, Jeff Harbour of Lockheed Martin Corp. for Cart3D is a collection of computer
viscosity, ratio of specific heats, Johnson Space Center. For further infor- programs for generating Cartesian
Reynolds number, and Prandtl num- mation, contact the Johnson Innovative Part- meshes [for computational fluid dy-
ber. Real-gas effects are taken into ac- nerships Office at [phone]. namics (CFD) and other applications]
count by treating the gases comprising MSC-23665 in volumes bounded by solid objects.
the mixture as both thermally and Aspects of Cart3D at earlier stages of
calorically imperfect. The Redlich- development were reported in “Robust
Kwong equation of state for mixtures Using a Quadtree Algorithm and Efficient Generation of Cartesian
and the constant-pressure ideal heat- To Assess Line of Sight Meshes for CFD” (ARC-14275), NASA
capacity equation for the mixture are A matched pair of computer algo- Tech Briefs, Vol. 23, No. 8 (August
used in combination with the depar- rithms determines whether line of sight 1999), page 30. The geometric input to
ture-function approach of thermody- (LOS) is obstructed by terrain. These Cart3D comprises surface triangula-
namics to obtain the equations for algorithms were originally designed for tions like those commonly generated
computing the flow properties. In addi- use in conjunction with combat-simula- by computer-aided-design programs.
tion to the aforementioned calcula- tion software in military training exer- Complexly shaped objects can be rep-
tions for air/R-134a mixtures, a re- cises, but could also be used for such resented as assemblies of simpler ones.
search version of MACHRK can commercial purposes as evaluating Cart3D deletes all portions of such an
perform the corresponding calcula- lines of sight for antennas or determin- assembled object that are not on the
tions for mixtures of air and R-12 ing what can be seen from a “room with exterior surface. Intersections between
(dichlorodifluoromethane) and for a view.” The quadtree preparation algo- components are preserved in the re-
air/SF mixtures. [R-12 was replaced by rithm operates on an array of digital el- sulting triangulation. A tie-breaking
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R-134a because of environmental con- evation data and only needs to be run routine unambiguously resolves geo-
cerns. SF has been considered for use once for a terrain region, which can be metric degeneracies. Then taking the
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in increasing the Reynolds-number quite large. Relatively little computa- intersected surface triangulation as
range.] tion time is needed, as each elevation input, the volume mesh is generated
This program was written by Ray Kvaternik value is considered only one and one- through division of cells of an initially
of Langley Research Center. Further infor- third times. The LOS assessment algo- coarse hexahedral grid. Cells are subdi-
mation is contained in a TSP (see page 1). rithm uses that quadtree to answer LOS vided to refine the grid in regions of in-
LAR-17095-1 queries. To determine whether LOS is creased surface curvature and/or in-
obstructed, a piecewise-planar (or creased flow gradients. Cells that
higher-order) terrain skin is computa- become split into multiple uncon-
Java Mission Evaluation tionally draped over the digital eleva- nected regions by thin pieces of sur-
Workstation System tion data. Adjustments are made to face are identified.
The Java Mission Evaluation Worksta- compensate for curvature of the Earth These programs were written by Michael J.
tion System (JMEWS) is a collection of and for refraction of the LOS by the at- Aftosmis and John E. Melton of Ames Re-
applications designed to retrieve, dis- mosphere. Average computing time ap- search Centerand Marsha J. Berger of the
play, and analyze both real-time and pears to be proportional to the number Courant Institute of Mathematics at New
recorded telemetry data. This software of queries times the logarithm of the York University. Further information is con-
is currently being used by both the number of elevation data points. Accu- tained in a TSP (see page 1).
Space Shuttle Program (SSP) and the racy is as high as is possible for the avail- Inquiries concerning rights for the commer-
International Space Station (ISS) pro- able elevation data, and symmetric re- cial use of this invention should be addressed
gram. JMEWS was written in the Java sults are assured. In the simulation, the to the Technology Partnerships Division,
programming language to satisfy the re- LOS query program runs as a separate Ames Research Center, (650) 604-2954.
quirement of platform independence. process, thereby making more random- Refer to ARC-14275-1.
NASA Tech Briefs, January 2006 11