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  • 1
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    FUN3D Manual: 13.5 (2019)
    In:  CASI
    Details
    Publication Date: 2019-05-24
    Description: This manual describes the installation and execution of FUN3D (Fully-UNstructured three-dimensional CFD (Computational Fluid Dynamics) code) version 13.5, including optional dependent packages. FUN3D is a suite of computational fluid dynamics simulation and design tools that uses mixed-element unstructured grids in a large number of formats, including structured multiblock and overset grid systems. A discretely-exact adjoint solver enables efficient gradient-based design and grid adaptation to reduce estimated discretization error. FUN3D is available with and without a reacting, real-gas capability. This generic gas option is available only for those persons that qualify for its beta release status.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: NASA/TM-2019-220271 , L-21013 , NF1676L-32825
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  • 2
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    Sixth Drag Prediction Workshop Results Using FUN3D with k-kL-MEAH2015 Turbulence Model (2017)
    In:  CASI
    Details
    Publication Date: 2019-06-15
    Description: The Common Research Model wing-body configuration is investigated with the k-kL-MEAH2015 turbulence model implemented in FUN3D. This includes results presented at the Sixth Drag Prediction Workshop and additional results generated after the workshop with a nonlinear Quadratic Constitutive Relation (QCR) variant of the same turbulence model. The workshop provided grids are used, and a uniform grid refinement study is performed at the design condition. A large variation between results with and without a reconstruction limiter is exhibited on medium grid sizes, indicating that the medium grid size is too coarse for drawing conclusions in comparison with experiment. This variation is reduced with grid refinement. At a fixed angle of attack near design conditions, the QCR variant yielded decreased lift and drag compared with the linear eddy-viscosity model by an amount that was approximately constant with grid refinement. The k-kL-MEAH2015 turbulence model produced wing root junction flow behavior consistent with wind tunnel observations.
    Keywords: Aircraft Design, Testing and Performance
    Type: NF1676L-26805 , Journal of Aircraft (ISSN 0021-8669) (e-ISSN 1533-3868); 55; 4; 1458-1468
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  • 3
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    Uncertainty Quantification of Turbulence Model Closure Coefficients for Transonic Wall-Bounded Flows (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The goal of this work was to quantify the uncertainty and sensitivity of commonly used turbulence models in Reynolds-Averaged Navier-Stokes codes due to uncertainty in the values of closure coefficients for transonic, wall-bounded flows and to rank the contribution of each coefficient to uncertainty in various output flow quantities of interest. Specifically, uncertainty quantification of turbulence model closure coefficients was performed for transonic flow over an axisymmetric bump at zero degrees angle of attack and the RAE 2822 transonic airfoil at a lift coefficient of 0.744. Three turbulence models were considered: the Spalart-Allmaras Model, Wilcox (2006) k-w Model, and the Menter Shear-Stress Trans- port Model. The FUN3D code developed by NASA Langley Research Center was used as the flow solver. The uncertainty quantification analysis employed stochastic expansions based on non-intrusive polynomial chaos as an efficient means of uncertainty propagation. Several integrated and point-quantities are considered as uncertain outputs for both CFD problems. All closure coefficients were treated as epistemic uncertain variables represented with intervals. Sobol indices were used to rank the relative contributions of each closure coefficient to the total uncertainty in the output quantities of interest. This study identified a number of closure coefficients for each turbulence model for which more information will reduce the amount of uncertainty in the output significantly for transonic, wall-bounded flows.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: NF1676L-20048 , AIAA Aviation 2015; Jun 22, 2015 - Jun 26, 2015; Dallas, TX; United States
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  • 4
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    Validation of a Node-Centered Wall Function Model for the Unstructured Flow Code FUN3D (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In this paper, the implementation of two wall function models in the Reynolds averaged Navier-Stokes (RANS) computational uid dynamics (CFD) code FUN3D is described. FUN3D is a node centered method for solving the three-dimensional Navier-Stokes equations on unstructured computational grids. The first wall function model, based on the work of Knopp et al., is used in conjunction with the one-equation turbulence model of Spalart-Allmaras. The second wall function model, also based on the work of Knopp, is used in conjunction with the two-equation k-! turbulence model of Menter. The wall function models compute the wall momentum and energy flux, which are used to weakly enforce the wall velocity and pressure flux boundary conditions in the mean flow momentum and energy equations. These wall conditions are implemented in an implicit form where the contribution of the wall function model to the Jacobian are also included. The boundary conditions of the turbulence transport equations are enforced explicitly (strongly) on all solid boundaries. The use of the wall function models is demonstrated on four test cases: a at plate boundary layer, a subsonic di user, a 2D airfoil, and a 3D semi-span wing. Where possible, different near-wall viscous spacing tactics are examined. Iterative residual convergence was obtained in most cases. Solution results are compared with theoretical and experimental data for several variations of grid spacing. In general, very good comparisons with data were achieved.
    Keywords: Fluid Mechanics and Thermodynamics; Aerodynamics
    Type: NF1676L-19849 , AIAA Aviation 2015; Jun 22, 2015 - Jun 26, 2015; Dallas, TX; United States
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  • 5
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    Toward Supersonic Retropropulsion CFD Validation (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper begins the process of verifying and validating computational fluid dynamics (CFD) codes for supersonic retropropulsive flows. Four CFD codes (DPLR, FUN3D, OVERFLOW, and US3D) are used to perform various numerical and physical modeling studies toward the goal of comparing predictions with a wind tunnel experiment specifically designed to support CFD validation. Numerical studies run the gamut in rigor from code-to-code comparisons to observed order-of-accuracy tests. Results indicate that this complex flowfield, involving time-dependent shocks and vortex shedding, design order of accuracy is not clearly evident. Also explored is the extent of physical modeling necessary to predict the salient flowfield features found in high-speed Schlieren images and surface pressure measurements taken during the validation experiment. Physical modeling studies include geometric items such as wind tunnel wall and sting mount interference, as well as turbulence modeling that ranges from a RANS (Reynolds-Averaged Navier-Stokes) 2-equation model to DES (Detached Eddy Simulation) models. These studies indicate that tunnel wall interference is minimal for the cases investigated; model mounting hardware effects are confined to the aft end of the model; and sparse grid resolution and turbulence modeling can damp or entirely dissipate the unsteadiness of this self-excited flow.
    Keywords: Aerodynamics
    Type: AIAA Paper 2011-3490 , NF1676L-12956 , 42nd AIAA Thermophysics Conference; Jun 27, 2011 - Jun 30, 2011; Honolulu, HI; United States
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  • 6
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    FUN3D Manual: 13.0 (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: This manual describes the installation and execution of FUN3D version 13.0, including optional dependent packages. FUN3D is a suite of computational fluid dynamics simulation and design tools that uses mixed-element unstructured grids in a large number of formats, including structured multiblock and overset grid systems. A discretely-exact adjoint solver enables efficient gradient-based design and grid adaptation to reduce estimated discretization error. FUN3D is available with and without a reacting, real-gas capability. This generic gas option is available only for those persons that qualify for its beta release status.
    Keywords: Computer Programming and Software
    Type: NASA/TM-2016-219330 , L-20735 , NF1676L-24988
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  • 7
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    Inflow/Outflow Boundary Conditions with Application to FUN3D (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: Several boundary conditions that allow subsonic and supersonic flow into and out of the computational domain are discussed. These boundary conditions are demonstrated in the FUN3D computational fluid dynamics (CFD) code which solves the three-dimensional Navier-Stokes equations on unstructured computational meshes. The boundary conditions are enforced through determination of the flux contribution at the boundary to the solution residual. The boundary conditions are implemented in an implicit form where the Jacobian contribution of the boundary condition is included and is exact. All of the flows are governed by the calorically perfect gas thermodynamic equations. Three problems are used to assess these boundary conditions. Solution residual convergence to machine zero precision occurred for all cases. The converged solution boundary state is compared with the requested boundary state for several levels of mesh densities. The boundary values converged to the requested boundary condition with approximately second-order accuracy for all of the cases.
    Keywords: Numerical Analysis
    Type: NASA/TM-2011-217181 , L-20011 , NF1676L-12459
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  • 8
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    Evaluation of Full Reynolds Stress Turbulence Models in FUN3D (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Full seven-equation Reynolds stress turbulence models are a relatively new and promising tool for todays aerospace technology challenges. This paper uses two stress-omega full Reynolds stress models to evaluate challenging flows including shock-wave boundary layer interactions, separation and mixing layers. The Wilcox and the SSGLRR full second-moment Reynolds stress models are evaluated for four problems: a transonic two-dimensional diffuser, a supersonic axisymmetric compression corner, a compressible planar shear layer, and a subsonic axisymmetric jet. Simulation results are compared with experimental data and results using the more commonly used Spalart-Allmaras (SA) one-equation and the Menter Shear Stress Transport (SST) two-equation models.
    Keywords: Fluid Mechanics and Thermodynamics; Aerodynamics
    Type: NASA/TM-2017-219468 , AIAA Paper 2017-0541 , E-19343 , GRC-E-DAA-TN39118 , AIAA Science and Technology (SciTech) Forum 2017; Jan 09, 2017 - Jan 13, 2017; Grapevine, TX; United States
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  • 9
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    Simulations of the NASA Langley 14- by 22-Foot Subsonic Tunnel for the Juncture Flow Experiment (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-30
    Description: NASAs Transformational Tools and Technologies Programs Juncture Flow experiment aims to provide data to improve Computational Fluid Dynamics (CFD) modeling in the juncture flow region. The experiment is planned to provide validation-quality data for CFD that focuses on the separation bubble near the wing-body juncture trailing edge region. Because wind tunnel tests associated with the Juncture Flow project have been designed for the purpose of CFD validation, considerable effort is going into modeling and simulating the wind tunnel. This is not only important because wind tunnel wall effects can play a role in integrated testing uncertainties, but also because the better the boundary conditions are known, the better CFD can accurately represent the experiment. This paper builds on the recent CFD efforts to model the NASA Langley 14- by 22-Foot Subsonic Tunnel. Current best practices in simulating wind tunnels are evaluated. The features of each method, as well as some of their pros and cons, are highlighted. Boundary conditions and modeling techniques currently used by CFD for empty-tunnel simulations are also described. Preliminary CFD studies associated with modeling the Juncture Flow model are summarized, with the intention to determine sensitivities of the flow near the wing-body juncture region of the model to a variety of modeling decisions.
    Keywords: Fluid Mechanics and Thermodynamics; Aircraft Design, Testing and Performance
    Type: STO-MP-AVT-284-02 , ARC-E-DAA-TN52010 , North Atlantic Treaty Organization Science and Technology Organization (NATO STO) AVT-284 Applied Vehicle Technology (AVT) Panel Research Workshop on Advanced Wind Tunnel Boundary Simulation; Apr 16, 2018 - Apr 18, 2018; Torino; Italy|Advanced Wind Tunnel Boundary Simulation STO-MP-AVT-284
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  • 10
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    FUN3D Manual: 12.7 (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: This manual describes the installation and execution of FUN3D version 12.7, including optional dependent packages. FUN3D is a suite of computational fluid dynamics simulation and design tools that uses mixed-element unstructured grids in a large number of formats, including structured multiblock and overset grid systems. A discretely-exact adjoint solver enables efficient gradient-based design and grid adaptation to reduce estimated discretization error. FUN3D is available with and without a reacting, real-gas capability. This generic gas option is available only for those persons that qualify for its beta release status.
    Keywords: Fluid Mechanics and Thermodynamics; Computer Programming and Software
    Type: NASA/TM2015218761 , L-20558 , NF1676L-21337
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