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  • 1
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    Euler/experiment correlations of sonic boom pressure signatures (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 30; 5; p. 669-675.
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Simulated Inlet Unstart and Nacelle/Diverter Effects for the Boeing Reference H Configuration (1999)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The Boeing Reference H configuration was tested in the NASA Ames 9x7 Supersonic Wind Tunnel. A simulated unstarted inlet was evaluated as well as the aerodynamic performance of the configuration with and without nacelle and diverter components. These experimental results were compared with computational results from the unstructured grid Euler flow solver AIRPLANE. The comparisons between computational and experimental results were good, and demonstrated that the Euler code is capable of efficiently and accurately predicting the changes in the aerodynamic coefficients associated with inlet unstart and the effects of the nacelle and diverter components.
    Keywords: Aerodynamics
    Type: First NASA/Industry High-Speed Research Configuration Aerodynamics Workshop; Part 3; 1285-1325; NASA/CP-1999-209690/PT3
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  • 3
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    Inlet Spillage Drag Predictions Using the AIRPLANE Code (1999)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: AIRPLANE (Jameson/Baker) is a steady inviscid unstructured Euler flow solver. It has been validated on many HSR geometries. It is implemented as MESHPLANE, an unstructured mesh generator, and FLOPLANE, an iterative flow solver. The surface description from an Intergraph CAD system goes into MESHPLANE as collections of polygonal curves to generate the 3D mesh. The flow solver uses a multistage time stepping scheme with residual averaging to approach steady state, but R is not time accurate. The flow solver was ported from Cray to IBM SP2 by Wu-Sun Cheng (IBM); it could only be run on 4 CPUs at a time because of memory limitations. Meshes for the four cases had about 655,000 points in the flow field, about 3.9 million tetrahedra, about 77,500 points on the surface. The flow solver took about 23 wall seconds per iteration when using 4 CPUs. It took about eight and a half wall hours to run 1,300 iterations at a time (the queue limit is 10 hours). A revised version of FLOPLANE (Thomas) was used on up to 64 CPUs to finish up some calculations at the end. We had to turn on more communication when using more processors to eliminate noise that was contaminating the flow field; this added about 50% to the elapsed wall time per iteration when using 64 CPUs. This study involved computing lift and drag for a wing/body/nacelle configuration at Mach 0.9 and 4 degrees pitch. Four cases were considered, corresponding to four nacelle mass flow conditions.
    Keywords: Aerodynamics
    Type: 1997 NASA High-Speed Research Program Aerodynamic Performance; Volume 1; Part 2; 1605-1648; NASA/CP-1999-209691/VOL1/PT2
    Format: text
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  • 4
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    Airplane Mesh Development with Grid Density Studies (1999)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Automatic Grid Generation Wish List Geometry handling, including CAD clean up and mesh generation, remains a major bottleneck in the application of CFD methods. There is a pressing need for greater automation in several aspects of the geometry preparation in order to reduce set up time and eliminate user intervention as much as possible. Starting from the CAD representation of a configuration, there may be holes or overlapping surfaces which require an intensive effort to establish cleanly abutting surface patches, and collections of many patches may need to be combined for more efficient use of the geometrical representation. Obtaining an accurate and suitable body conforming grid with an adequate distribution of points throughout the flow-field, for the flow conditions of interest, is often the most time consuming task for complex CFD applications. There is a need for a clean unambiguous definition of the CAD geometry. Ideally this would be carried out automatically by smart CAD clean up software. One could also define a standard piece-wise smooth surface representation suitable for use by computational methods and then create software to translate between the various CAD descriptions and the standard representation. Surface meshing remains a time consuming, user intensive procedure. There is a need for automated surface meshing, requiring only minimal user intervention to define the overall density of mesh points. The surface mesher should produce well shaped elements (triangles or quadrilaterals) whose size is determined initially according to the surface curvature with a minimum size for flat pieces, and later refined by the user in other regions if necessary. Present techniques for volume meshing all require some degree of user intervention. There is a need for fully automated and reliable volume mesh generation. In addition, it should be possible to create both surface and volume meshes that meet guaranteed measures of mesh quality (e.g. minimum and maximum angle, stretching ratios, etc.).
    Keywords: Aerodynamics
    Type: 1998 NASA High-Speed Research Program Aerodynamic Performance Workshop; Volume 1; Part 1; 75-145; NASA/CP-1999-209692/VOL1/PT1
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  • 5
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    Improvements to the Unstructured Mesh Generator MESH3D (1999)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The AIRPLANE process starts with an aircraft geometry stored in a CAD system. The surface is modeled with a mesh of triangles and then the flow solver produces pressures at surface points which may be integrated to find forces and moments. The biggest advantage is that the grid generation bottleneck of the CFD process is eliminated when an unstructured tetrahedral mesh is used. MESH3D is the key to turning around the first analysis of a CAD geometry in days instead of weeks. The flow solver part of AIRPLANE has proven to be robust and accurate over a decade of use at NASA. It has been extensively validated with experimental data and compares well with other Euler flow solvers. AIRPLANE has been applied to all the HSR geometries treated at Ames over the course of the HSR program in order to verify the accuracy of other flow solvers. The unstructured approach makes handling complete and complex geometries very simple because only the surface of the aircraft needs to be discretized, i.e. covered with triangles. The volume mesh is created automatically by MESH3D. AIRPLANE runs well on multiple platforms. Vectorization on the Cray Y-MP is reasonable for a code that uses indirect addressing. Massively parallel computers such as the IBM SP2, SGI Origin 2000, and the Cray T3E have been used with an MPI version of the flow solver and the code scales very well on these systems. AIRPLANE can run on a desktop computer as well. AIRPLANE has a future. The unstructured technologies developed as part of the HSR program are now targeting high Reynolds number viscous flow simulation. The pacing item in this effort is Navier-Stokes mesh generation.
    Keywords: Computer Programming and Software
    Type: 1999 NASA High-Speed Research Program Aerodynamic Performance Workshop; Volume 1; Part 1; 213-252; NASA/CP-1999-209704/VOL1/PT1
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  • 6
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    Unstructured Euler flow solutions using hexahedral cell refinement (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An attempt is made to extend grid refinement into three dimensions by using unstructured hexahedral grids. The flow solver is developed using the TIGER (topologically Independent Grid, Euler Refinement) as the starting point. The program uses an unstructured hexahedral mesh and a modified version of the Jameson four-stage, finite-volume Runge-Kutta algorithm for integration of the Euler equations. The unstructured mesh allows for local refinement appropriate for each freestream condition, thereby concentrating mesh cells in the regions of greatest interest. This increases the computational efficiency because the refinement is not required to extend throughout the entire flow field.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 91-0637
    Format: text
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  • 7
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    Euler/experiment correlations of sonic boom pressure signatures (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: The ability of inviscid computational fluid dynamics (CFD) codes to compute sonic boom pressure signatures is examined using three different codes that solve the Euler equations of fluid flow on structured hexahedral and unstructured tetrahedral grids. The results of these Euler codes were evaluated by comparing the computed pressure signatures with near-field experimental data. The computational pressure signatures were determined at distances of one body length or less below the configuration in the plane of symmetry and extrapolated to experimental distances. The extrapolated CFD pressure signatures gave acceptable correlations with experimental data, provided that fine grids were used near the surface and downstream of the configuration.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 91-3276 , AIAA Applied Aerodynamics Conference; Sept. 23-25, 1991; Baltimore, MD; United States
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  • 8
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    An edge-based solution-adaptive method applied to the AIRPLANE code (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Computational methods to solve large-scale realistic problems in fluid flow can be made more efficient and cost effective by using them in conjunction with dynamic mesh adaption procedures that perform simultaneous coarsening and refinement to capture flow features of interest. This work couples the tetrahedral mesh adaption scheme, 3D_TAG, with the AIRPLANE code to solve complete aircraft configuration problems in transonic and supersonic flow regimes. Results indicate that the near-field sonic boom pressure signature of a cone-cylinder is improved, the oblique and normal shocks are better resolved on a transonic wing, and the bow shock ahead of an unstarted inlet is better defined.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-199754 , NAS 1.26:199754 , RIACS-TR-95-22 , AIAA PAPER 96-0553 , NIPS-95-06387 , AIAA 34th Aerospace Sciences Meeting and Exhibit; Jan 15, 1996 - Jan 18, 1996; Reno, NV; United States
    Format: application/pdf
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  • 9
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    Refinement Of Hexahedral Cells In Euler Flow Computations (1996)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Topologically Independent Grid, Euler Refinement (TIGER) computer program solves Euler equations of three-dimensional, unsteady flow of inviscid, compressible fluid by numerical integration on unstructured hexahedral coordinate grid refined where necessary to resolve shocks and other details. Hexahedral cells subdivided, each into eight smaller cells, as needed to refine computational grid in regions of high flow gradients. Grid Interactive Refinement and Flow-Field Examination (GIRAFFE) computer program written in conjunction with TIGER program to display computed flow-field data and to assist researcher in verifying specified boundary conditions and refining grid.
    Keywords: MECHANICS
    Type: ARC-13077 , NASA Tech Briefs (ISSN 0145-319X); 20; 3; P. 74
    Format: text
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  • 10
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    Fast viscous correction method for full-potential transonic wing analysis (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 24; 218-220
    Format: text
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