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Full Multigrid Flow Solver
Tuesday, 01 November 2005
FMG3D (full multigrid 3 dimensions) is a pilot computer program that solves equations of fluid flow using a finite difference representation on a structured grid. Infrastructure exists for three dimensions but the current implementation treats only two dimensions. Written in Fortran 90, FMG3D takes advantage of the recursive subroutine feature, dynamic memory allocation, and structuredprogramming constructs of that language. FMG3D supports multiblock grids with three types of block to block interfaces: periodic, Czero, and Cinfinity. For all three types, grid points must match at interfaces. For periodic and Cinfinity types, derivatives of grid metrics must be continuous at interfaces. The available equation sets are as follows: scalar elliptic equations, scalar convection equations, and the pressurePoisson formulation of the NavierStokes equations for an incompressible fluid. All the equation sets are implemented with nonzero forcing functions to enable the use of userspecified solutions to assist in verification and validation. The equations are solved with a full multigrid scheme using a full approximation scheme to converge the solution on each succeeding grid level. Restriction to the next coarser mesh uses direct injection for variables and full weighting for residual quantities; prolongation of the coarse grid correction from the coarse mesh to the fine mesh uses bilinear interpolation; and prolongation of the coarse grid solution uses bicubic interpolation.
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Virtual Machine Language
Tuesday, 01 November 2005
Virtual Machine Language (VML) is a missionindependent, reusable software system for programming for spacecraft operations. Features of VML include a rich set of data types, named functions, parameters, IF and WHILE control structures, polymorphism, and onthefly creation of spacecraft commands from calculated values. Spacecraft functions can be abstracted into named blocks that reside in files aboard the spacecraft. These named blocks accept parameters and execute in a repeatable fashion. The sizes of uplink products are minimized by the ability to call blocks that implement most of the command steps. This block approach also enables some autonomous operations aboard the spacecraft, such as aerobraking, telemetry conditional monitoring, and anomaly response, without developing autonomous flight software. Operators on the ground write blocks and command sequences in a concise, highlevel, humanreadable programming language (also called “VML”). A compiler translates the humanreadable blocks and command sequences into binary files (the operations products). The flight portion of VML interprets the uplinked binary files. The ground subsystem of VML also includes an interactive sequenceexecution tool hosted on workstations, which runs sequences at several thousand times realtime speed, affords debugging, and generates reports. This tool enables iterative development of blocks and sequences within times of the order of seconds.
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TwoDimensional Ffowcs Williams/Hawkings Equation Solver
Tuesday, 01 November 2005
FWH2D is a Fortran 90 computer program that solves a twodimensional (2D) version of the equation, derived by J. E. Ffowcs Williams and D. L. Hawkings, for sound generated by turbulent flow. FWH2D was developed especially for estimating noise generated by airflows around such approximately 2D airframe components as slats. The user provides input data on fluctuations of pressure, density, and velocity on some surface. These data are combined with information about the geometry of the surface to calculate histories of thickness and loading terms. These histories are fast Fouriertransformed into the frequency domain. For each frequency of interest and each observer position specified by the user, kernel functions are integrated over the surface by use of the trapezoidal rule to calculate a pressure signal. The resulting frequencydomain signals are inversefastFouriertransformed back into the time domain. The output of the code consists of the time and frequency domain representations of the pressure signals at the observer positions. Because of its approximate nature, FWH2D overpredicts the noise from a finitelength (3D) component. The advantage of FWH2D is that it requires a fraction of the computation time of a 3D Ffowcs Williams/Hawkings solver.
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Posted in: Briefs, TSP
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AutoChem
Tuesday, 01 November 2005
AutoChem is a suite of Fortran 90 computer programs for the modeling of kinetic reaction systems. AutoChem performs automatic code generation, symbolic differentiation, analysis, and documentation. It produces a documented standalone system for the modeling and assimilation of atmospheric chemistry. Given databases of chemical reactions and a list of constituents defined by the user, AutoChem automatically does the following:
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DataAcquisition Software for PSP/TSP WindTunnel Cameras
Saturday, 01 October 2005
WingViewer is a computer program for acquisition and reduction of image data acquired by any of five different scientific grade commercial electronic cameras used at Langley Research center to observe windtunnel models coated with pressure or temperaturesensitive paints (PSP/TSP).
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Grid Visualization Tool
Saturday, 01 October 2005
The Grid Visualization Tool (GVT) is a computer program for displaying the path of a mobile robotic explorer (rover) on a terrain map. The GVT reads a mapdata file in either portable graymap (PGM) or portable pixmap (PPM) format, representing a grayscale or color map image, respectively.
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Updated Chemical Kinetics and Sensitivity Analysis Code
Saturday, 01 October 2005
An updated version of the General Chemical Kinetics and Sensitivity Analysis (LSENS) computer code has become available. A prior version of LSENS was described in “Program Helps to Determine ChemicalReaction Mechanisms” (LEW15758), NASA Tech Briefs, Vol. 19, No. 5 (May 1995), page 66.
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