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  • 1
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    Extrusion of Complex Surface Meshes Utilizing Face Offsetting and Mean Curvature Smoothing (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: Grids for three-dimensional Computational Fluid Dynamics problems frequently require a prismatic layer of cells, typically extruded in the off-body direction from a two-dimensional surface mesh to properly resolve boundary layers. When the surface geometry is complex, the extrusion process can fail, resulting in the physical boundary layer being thicker than the prismatic layer, leading to under-resolved boundary layers. To address the shortcomings of existing grid generation tools, a new tool has been developed as part of the Mesh Tools suite, that is capable of extruding complex surface meshes. The new tool uses a face offsetting method to preserve surface curvature and a mean curvature smoothing algorithm to prevent the cells from self-intersecting in concave regions. Testing of the new tool found that not only were complex surface meshes able to be extruded to the desired thickness, but extrusion of simple surface meshes was also improved, due to the face offsetting method.
    Keywords: Numerical Analysis; Fluid Mechanics and Thermodynamics
    Type: JSC-E-DAA-TN63010 , AIAA SciTech Forum 2019; Jan 07, 2019 - Jan 11, 2019; San Diego, CA; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Thermal Analysis System (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: A thermal fluid system modeler including a plurality of individual components. A solution vector is configured and ordered as a function of one or more inlet dependencies of the plurality of individual components. A fluid flow simulator simulates thermal energy being communicated with the flowing fluid and between first and second components of the plurality of individual components. The simulation extends from an initial time to a later time step and bounds heat transfer to be substantially between the flowing fluid, walls of tubes formed in each of the individual components of the plurality, and between adjacent tubes. Component parameters of the solution vector are updated with simulation results for each of the plurality of individual components of the simulation.
    Keywords: Computer Programming and Software; Fluid Mechanics and Thermodynamics
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    NASA TECHNICAL REPORTS
  • 3
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    Analysis of Fluid Flow over a Surface (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: A method, apparatus, and computer program product for modeling heat radiated by a structure. The flow of a fluid over a surface of a model of the structure is simulated. The surface has a plurality of surface elements. Heat radiated by the plurality of surface elements in response to the fluid flowing over the surface of the model of the structure is identified. An effect of heat radiated by at least a portion of the plurality of surface elements on each other is identified. A model of the heat radiated by the structure is created using the heat radiated by the plurality of surface elements and the effect of the heat radiated by at least a portion of the plurality of surface elements on each other.
    Keywords: Aeronautics (General); Fluid Mechanics and Thermodynamics
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    NASA TECHNICAL REPORTS
  • 4
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    Effects of Free Molecular Heating on the Space Shuttle Active Thermal Control System (2007)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: During Space Transportation System (STS) flight 121, higher than predicted radiator outlet temperatures were experienced from post insertion and up until nominal correction (NC) burn two. Effects from the higher than predicted heat loads on the radiator panels led to an additional 50 lbm of supply water consumed by the Flash Evaporator System (FES). Post-flight analysis and research revealed that the additional heat loads were due to Free Molecular Heating (FMH) on the radiator panels, which previously had not been considered as a significant environmental factor for the Space Shuttle radiators. The current Orbiter radiator heat flux models were adapted to incorporate the effects of FMH in addition to solar, earth infrared and albedo sources. Previous STS flights were also examined to find additional flight data on the FMH environment. Results of the model were compared to flight data and verified against results generated by the National Aeronautics and Space Administration (NASA), Johnson Space Center (JSC) Aero-sciences group to verify the accuracy of the model.
    Keywords: Spacecraft Design, Testing and Performance
    Type: 46th AIAA Aerospace Sciences Meeting and Exhibit; Jan 07, 2008 - Jan 10, 2008; Reno, NV; United States
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    NASA TECHNICAL REPORTS
  • 5
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    Best Practices for Unstructured Grid Shock Fitting (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Unstructured grid solvers have well-known issues predicting surface heat fluxes when strong shocks are present. Various efforts have been made to address the underlying numerical issues that cause the erroneous predictions. The present work addresses some of the shortcomings of unstructured grid solvers, not by addressing the numerics, but by applying structured grid best practices to unstructured grids. A methodology for robust shock detection and shock fitting is outlined and applied to production relevant cases. Results achieved by using the Loci-CHEM Computational Fluid Dynamics solver are provided.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: JSC-CN-36483 , AIAA SciTech 2017; Jan 09, 2017 - Jan 13, 2017; Grapevine, TX; United States
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    NASA TECHNICAL REPORTS
  • 6
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    Comparison of CFD Predictions with Shuttle Global Flight Thermal Imagery and Discrete Surface Measurements (2010)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Surface temperature measurements from the STS-119 boundary-layer transition experiment on the space shuttle orbiter Discovery provide a rare opportunity to assess turbulent CFD models at hypersonic flight conditions. This flight data was acquired by on-board thermocouples and by infrared images taken off-board by the Hypersonic Thermodynamic Infrared Measurements (HYTHIRM) team, and is suitable for hypersonic CFD turbulence assessment between Mach 6 and 14. The primary assessment is for the Baldwin-Lomax and Cebeci-Smith algebraic turbulence models in the DPLR and LAURA CFD codes, respectively. A secondary assessment is made of the Shear-Stress Transport (SST) two-equation turbulence model in the DPLR code. Based upon surface temperature comparisons at eleven thermocouple locations, the algebraic-model turbulent CFD results average 4% lower than the measurements for Mach numbers less than 11. For Mach numbers greater than 11, the algebraic-model turbulent CFD results average 5% higher than the three available thermocouple measurements. Surface temperature predictions from the two SST cases were consistently 3 4% higher than the algebraic-model results. The thermocouple temperatures exhibit a change in trend with Mach number at about Mach 11; this trend is not reflected in the CFD results. Because the temperature trends from the turbulent CFD simulations and the flight data diverge above Mach 11, extrapolation of the turbulent CFD accuracy to higher Mach numbers is not recommended.
    Keywords: Aerodynamics
    Type: AIAA Paper 2010-454 , LF99-9994 , 48th AIAA Aerospace Sciences Meeting; Jan 04, 2010 - Jan 07, 2010; Orlando, FL; United States
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    NASA TECHNICAL REPORTS
  • 7
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    Thermal Protection System Cavity Heating for Simplified and Actual Geometries Using Computational Fluid Dynamics Simulations with Unstructured Grids (2010)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Thermal Protection System (TPS) Cavity Heating is predicted using Computational Fluid Dynamics (CFD) on unstructured grids for both simplified cavities and actual cavity geometries. Validation was performed using comparisons to wind tunnel experimental results and CFD predictions using structured grids. Full-scale predictions were made for simplified and actual geometry configurations on the Space Shuttle Orbiter in a mission support timeframe.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: JSC-CN-21924 , AIAA Thermophysics Conference 2011; Jun 27, 2011 - Jun 30, 2011; Honolulu, HI; United States
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    NASA TECHNICAL REPORTS
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