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  • 1
    Publication Date: 2011-08-24
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 30; 6, Ju; 1457-146
    Format: text
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  • 2
    Publication Date: 2013-08-31
    Description: Techniques are presented for quickly finding a multiblock grid for a 2D geometrically complex domain from geometrical boundary data. An automated technique for determining a block decomposition of the domain is explained. Techniques for representing this domain decomposition and transforming it are also presented. Further, a linear optimization method may be used to solve the equations which determine grid dimensions within the block decomposition. These algorithms automate many stages in the domain decomposition and grid formation process and limit the need for human intervention and inputs. They are demonstrated for the meridional or throughflow geometry of a bladed jet engine configuration.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA. Langley Research Center, Software Surface Modeling and Grid Generation Steering Committee; p 477-485
    Format: application/pdf
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  • 3
    Publication Date: 2013-08-29
    Description: The goal was to create methods for generating grids with minimal human intervention that are applicable to a wide range of problems and compatible with existing numerical methods and with existing and proposed computers. The following topics that are related to multiblock grid generation are briefly covered in viewgraph form: finding a domain decomposition, dimensioning grids, grid smoothing, manipulating grids and decompositions, and some specializations for jet engine configurations.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Workshop on Grid Generation and Related Areas; p 79-84
    Format: text
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  • 4
    Publication Date: 2019-01-25
    Description: A two dimensional nonaxisymmetric Euler solution in a geometric representation of a jet engine configuration without blades is presented. The domain, including internal and external flow, is covered with a multiblock grid. To construct the grid, a domain decomposition technique is used to subdivide the domain and smooth grids are dimensioned and placed in each block. The grid contains 44 blocks which cover the external field, the inlet, bypass duct, core duct and nozzle of the nonaxisymmetric engine configuration. The geometry is symmetric about the meanline of the hub, but the grid is not since there is no symmetry condition applied to the grid between the two halves. With a symmetric grid at zero angle of attack, the measures of the solution would cancel exactly. With an asymmetric grid, the solution will not necessarily be symmetric and the lift coefficient will not necessarily be zero. Thus, grid asymmetry can be exploited to verify the resolution of the solution. The solution may be verified on the basis of five theoretical quantities: conservation of mass and energy, deviation of the lift coefficient from zero, deviation of the drag coefficient from zero, deviations from constant entropy, and deviations in the pressure distributions over the symmetric surfaces of the components. This technique is suitable for obtaining numerical solutions in complex geometries and provides a foundation for complete engine throughflow calculations.
    Keywords: AERODYNAMICS
    Type: CASI, Proceedings of the 3rd Canadian Symposium on Aerodynamics; p 186-193
    Format: text
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  • 5
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    In:  Other Sources
    Publication Date: 2019-06-28
    Description: An Euler solution for an axisymmetric jet engine configuration without blade effects is presented. The Euler equations are solved on a multiblock grid which covers a domain including the inlet, bybass duct, core passage, nozzle, and the far field surrounding the engine. The simulation is verified by considering five theoretical properties of the solution. The solution demonstrates both multiblock grid generation techniques and a foundation for a full jet engine throughflow calculation.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 92-0544
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  • 6
    Publication Date: 2019-07-13
    Description: This paper presents an analysis and simulation of evaporation and condensation at a motionless liquid/vapor interface. A 1-D model equation, emphasizing heat and mass transfer at the interface, is solved in two ways, and incorporated into a subgrid interface model within a CFD simulation. Simulation predictions are compared with experimental data from the CPST Engineering Design Unit tank, a cryogenic fluid management test tank in 1-g. The numerical challenge here is the physics of the liquid/vapor interface; pressurizing the ullage heats it by several degrees, and sets up an interfacial temperature gradient that transfers heat to the liquid phase-the rate limiting step of condensation is heat conducted through the liquid and vapor. This physics occurs in thin thermal layers O(1 mm) on either side of the interface which is resolved by the subgrid interface model. An accommodation coefficient of 1.0 is used in the simulations which is consistent with theory and measurements. This model is predictive of evaporation/condensation rates, that is, there is no parameter tuning.
    Keywords: Fluid Mechanics and Thermodynamics; Propellants and Fuels
    Type: GRC-E-DAA-TN43540 , AIAA Propulsion and Energy Forum and Exposition; Jul 10, 2017 - Jul 12, 2017; Atlanta, GA; United States
    Format: application/pdf
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  • 7
    Publication Date: 2019-07-10
    Description: This paper develops a procedure to statically analyze aspects of the meaning or semantics of scientific and engineering code. The analysis involves adding semantic declarations to a user's code and parsing this semantic knowledge with the original code using multiple expert parsers. These semantic parsers are designed to recognize formulae in different disciplines including physical and mathematical formulae and geometrical position in a numerical scheme. In practice, a user would submit code with semantic declarations of primitive variables to the analysis procedure, and its semantic parsers would automatically recognize and document some static, semantic concepts and locate some program semantic errors. A prototype implementation of this analysis procedure is demonstrated. Further, the relationship between the fundamental algebraic manipulations of equations and the parsing of expressions is explained. This ability to locate some semantic errors and document semantic concepts in scientific and engineering code should reduce the time, risk, and effort of developing and using these codes.
    Keywords: Mathematical and Computer Sciences (General)
    Type: NASA/CR-1998-207402 , NAS 1.26:207402 , E-11149
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  • 8
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    In:  Other Sources
    Publication Date: 2019-07-13
    Description: This paper concerns a procedure that analyzes aspects of the meaning or semantics of scientific and engineering code. This procedure involves taking a user's existing code, adding semantic declarations for some primitive variables, and parsing this annotated code using multiple, distributed expert parsers. These semantic parser are designed to recognize formulae in different disciplines including physical and mathematical formulae and geometrical position in a numerical scheme. The parsers will automatically recognize and document some static, semantic concepts and locate some program semantic errors. Results are shown for a subroutine test case and a collection of combustion code routines. This ability to locate some semantic errors and document semantic concepts in scientific and engineering code should reduce the time, risk, and effort of developing and using these codes.
    Keywords: Computer Programming and Software
    Type: May 27, 1998 - May 31, 1998; Vancouver, British Columbia; Canada
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  • 9
    Publication Date: 2019-07-13
    Description: Physical and mathematical formulae and concepts are fundamental elements of scientific and engineering software. These classical equations and methods are time tested, universally accepted, and relatively unambiguous. The existence of this classical ontology suggests an ideal problem for automated comprehension. This problem is further motivated by the pervasive use of scientific code and high code development costs. To investigate code comprehension in this classical knowledge domain, a research prototype has been developed. The prototype incorporates scientific domain knowledge to recognize code properties (including units, physical, and mathematical quantity). Also, the procedure implements programming language semantics to propagate these properties through the code. This prototype's ability to elucidate code and detect errors will be demonstrated with state of the art scientific codes.
    Keywords: Computer Programming and Software
    Type: Ninth International Workshop on Program Comprehension; May 12, 2001 - May 13, 2001; Toronto, Ontario; Canada
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  • 10
    Publication Date: 2019-07-13
    Description: A two dimensional, nonaxisymmetric Euler solution in a geometry representative of a jet engine configuration without blades is presented. The domain, including internal and external flow, is covered with a multiblock grid. In order to construct this grid, a domain decomposition technique is used to subdivide the domain, and smooth grids are dimensioned and placed in each block. The Euler solution is verified by examining five theoretical properties. The result demonstrates techniques for performing numerical solutions in complex geometries and provides a foundation for complete engine throughflow calculations.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-105329 , ICOMP-91-22 , E-6691 , NAS 1.15:105329 , Canadian Symposium on Aerodynamics; Nov 20, 1991 - Nov 21, 1991; Toronto (Ontario); Canada
    Format: application/pdf
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