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  • Aerodynamics  (4)
  • Research and Support Facilities (Air)  (3)
  • Nonmetallic Materials  (2)
  • 2000-2004  (4)
  • 1995-1999  (5)
  • 1960-1964
  • 1
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    New Spray Bar System Installed in NASA Lewis' Icing Research Tunnel (1998)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: NASA Lewis Research Center's Icing Research Tunnel (IRT) is the world's largest refrigerated wind tunnel dedicated to the study of aircraft icing. In the IRT, natural icing conditions are duplicated to test the effects of in-flight icing on actual aircraft components and on scale models of airplanes and helicopters. The IRT's ability to reproduce a natural icing cloud was significantly improved with the recent installation of a new spray bar system. It is the spray bar system that transforms the low-speed wind tunnel into an icing wind tunnel by producing microscopic droplets of water and injecting them into the wind tunnel air stream in order to accurately simulate cloud moisture.
    Keywords: Research and Support Facilities (Air)
    Type: Research and Technology 1997; NASA/TM-1998-206312
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Prediction of High-Lift Flows using Turbulent Closure Models (1997)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: The flow over two different multi-element airfoil configurations is computed using linear eddy viscosity turbulence models and a nonlinear explicit algebraic stress model. A subset of recently-measured transition locations using hot film on a McDonnell Douglas configuration is presented, and the effect of transition location on the computed solutions is explored. Deficiencies in wake profile computations are found to be attributable in large part to poor boundary layer prediction on the generating element, and not necessarily inadequate turbulence modeling in the wake. Using measured transition locations for the main element improves the prediction of its boundary layer thickness, skin friction, and wake profile shape. However, using measured transition locations on the slat still yields poor slat wake predictions. The computation of the slat flow field represents a key roadblock to successful predictions of multi-element flows. In general, the nonlinear explicit algebraic stress turbulence model gives very similar results to the linear eddy viscosity models.
    Keywords: Aerodynamics
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Prediction of Airfoil Characteristics With Higher Order Turbulence Models (1996)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This study focuses on the prediction of airfoil characteristics, including lift and drag over a range of Reynolds numbers. Two different turbulence models, which represent two different types of models, are tested. The first is a standard isotropic eddy-viscosity two-equation model, and the second is an explicit algebraic stress model (EASM). The turbulent flow field over a general-aviation airfoil (GA(W)-2) at three Reynolds numbers is studied. At each Reynolds number, predicted lift and drag values at different angles of attack are compared with experimental results, and predicted variations of stall locations with Reynolds number are compared with experimental data. Finally, the size of the separation zone predicted by each model is analyzed, and correlated with the behavior of the lift coefficient near stall. In summary, the EASM model is able to predict the lift and drag coefficients over a wider range of angles of attack than the two-equation model for the three Reynolds numbers studied. However, both models are unable to predict the correct lift and drag behavior near the stall angle, and for the lowest Reynolds number case, the two-equation model did not predict separation on the airfoil near stall.
    Keywords: Aerodynamics
    Type: NASA-TM-110246 , NAS 1.15:110246
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    X-Ray Diffraction and Imaging Study of Imperfections of Crystallized Lysozyme with Coherent X-Rays (2003)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Phase-sensitive x-ray diffraction imaging and high angular-resolution diffraction combined with phase contrast radiographic imaging are employed to characterize defects and perfection of a uniformly grown tetragonal lysozyme crystal in symmetric Laue case. The fill width at half-maximum (FWHM) of a 4 4 0 rocking curve measured from the original crystal is approximately 16.7 arcseconds, and defects, which include point defects, line defects, and microscopic domains, have been clearly observed in the diffraction images of the crystal. The observed line defects carry distinct dislocation features running approximately along the 〈110〉 growth front, and they have been found to originate mostly at a central growth area and occasionally at outer growth regions. Individual point defects trapped at a crystal nucleus are resolved in the images of high sensitivity to defects. Slow dehydration has led to the broadening of the 4 4 0 rocking curve by a factor of approximately 2.4. A significant change of the defect structure and configuration with drying has been revealed, which suggests the dehydration induced migration and evolution of dislocations and lattice rearrangements to reduce overall strain energy. The sufficient details of the observed defects shed light upon perfection, nucleation and growth, and properties of protein crystals.
    Keywords: Nonmetallic Materials
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Surface Relaxation in Protein Crystals (2002)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Surface X-ray diffraction measurements were performed on (111) growth faces of crystals of the Cellular iron-storage protein horse spleen ferritin. Crystal Trunkation Rods (CTR) were measured. A fit of the measured profile of the CTR revealed a surface roughness of 48 +/- 4.5 A and a top layer spacing contraction of 3.9 +/- 1.5%. In addition to the peak from the CTR, the rocking curves of the crystals displayed unexpected extra peaks. Multiple-scattering is demonstrated to account for them. Future applications of the method could allow the exploration of hydration effects on the growth of protein crystals.
    Keywords: Nonmetallic Materials
    Format: text
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  • 6
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    New Icing Cloud Simulation System at the NASA Glenn Research Center Icing Research Tunnel (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A new spray bar system was designed, fabricated, and installed in the NASA Glenn Research Center's Icing Research Tunnel (IRT). This system is key to the IRT's ability to do aircraft in-flight icing cloud simulation. The performance goals and requirements levied on the design of the new spray bar system included increased size of the uniform icing cloud in the IRT test section, faster system response time, and increased coverage of icing conditions as defined in Appendix C of the Federal Aviation Regulation (FAR), Part 25 and Part 29. Through significant changes to the mechanical and electrical designs of the previous-generation spray bar system, the performance goals and requirements were realized. Postinstallation aerodynamic and icing cloud calibrations were performed to quantify the changes and improvements made to the IRT test section flow quality and icing cloud characteristics. The new and improved capability to simulate aircraft encounters with in-flight icing clouds ensures that the 1RT will continue to provide a satisfactory icing ground-test simulation method to the aeronautics community.
    Keywords: Research and Support Facilities (Air)
    Type: NASA/TM-1999-208891 , NAS 1.15:208891 , AIAA Paper 98-0143 , E-11477 , Aerospace Sciences; Jan 12, 1998 - Jan 15, 1998; Reno, NV; United States
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  • 7
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    Overview of the Icing and Flow Quality Improvements Program for the NASA Glenn Icing Research Tunnel (2001)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Major upgrades were made in 1999 to the 6- by 9-Foot (1.8- by 2.7-m) Icing Research Tunnel (IRT) at the NASA Glenn Research Center. These included replacement of the electronic controls for the variable-speed drive motor, replacement of the heat exchanger, complete replacement and enlargement of the leg of the tunnel containing the new heat-exchanger, the addition of flow-expanding and flow-contracting turning vanes upstream and downstream of the heat exchanger, respectively, and the addition of fan outlet guide vanes (OGV's). This paper describes the rationale behind this latest program of IRT upgrades and the program's requirements and goals. An overview is given of the scope of work undertaken by the design and construction contractors, the scale-model IRT (SMIRT) design verification program, the comprehensive reactivation test program initiated upon completion of construction, and the overall management approach followed.
    Keywords: Research and Support Facilities (Air)
    Type: NASA/TM-2001-210686 , NAS 1.15:210686 , E-12613 , AIAA Paper 2001-0229 , 39th Aerospace Sciences Meeting and Exhibit; Jan 08, 2001 - Jan 11, 2001; Reno, NV; United States
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  • 8
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    Prediction of Transonic Vortex Flows Using Linear and Nonlinear Turbulent Eddy Viscosity Models (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Three-dimensional transonic flow over a delta wing is investigated with a focus on the effect of transition and influence of turbulence stress anisotropies. The performance of linear eddy viscosity models and an explicit algebraic stress model is assessed at the start of vortex flow, and the results compared with experimental data. To assess the effect of transition location, computations that either fix transition or are fully turbulent are performed. To assess the effect of the turbulent stress anisotropy, comparisons are made between predictions from the algebraic stress model and the linear eddy viscosity models. Both transition location and turbulent stress anisotropy significantly affect the 3D flow field. The most significant effect is found to be the modeling of transition location. At a Mach number of 0.90, the computed solution changes character from steady to unsteady depending on transition onset. Accounting for the anisotropies in the turbulent stresses also considerably impacts the flow, most notably in the outboard region of flow separation.
    Keywords: Aerodynamics
    Type: NASA/TM-2000-210282 , L-17986 , NAS 1.15:210282
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  • 9
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    Prediction of Complex Aerodynamic Flows with Explicit Algebraic Stress Models (1996)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An explicit algebraic stress equation, developed by Gatski and Speziale, is used in the framework of K-epsilon formulation to predict complex aerodynamic turbulent flows. The nonequilibrium effects are modeled through coefficients that depend nonlinearly on both rotational and irrotational strains. The proposed model was implemented in the ISAAC Navier-Stokes code. Comparisons with the experimental data are presented which clearly demonstrate that explicit algebraic stress models can predict the correct response to nonequilibrium flow.
    Keywords: Aerodynamics
    Type: NASA-CR-202580 , NAS 1.26:202580 , AIAA Paper 96-0565 , Aerospace Sciences; Jan 15, 1996 - Jan 18, 1996; Reno, NV; United States
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