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  • 1
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    Experimental studies of transonic flow field near a longitudinally slotted wind tunnel wall (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The results of detailed parametric experiments are presented for the near-wall flow field of a longitudinally slotted transonic wind tunnel. Existing data are reevaluated and new data obtained in the Langley 6- by 19-inch Transonic Wind Tunnel are presented and analyzed. In the experiments, researchers systematically investigate many pertinent wall-geometry variables such as the wall openness and the number of slots along with the free stream Mach number and model angle of attack. Flow field surveys on the plane passing through the centerline of the slot were conducted and are presented. The effects of viscosity on the slot flow are considered in the analysis. The present experiments, combined with those of previous investigations, give a more complete physical characterization of the flow near and through the slotted wall of a transonic wind tunnel.
    Keywords: AERODYNAMICS
    Type: NASA-TP-3392 , L-16423 , NAS 1.60:3392
    Format: application/pdf
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  • 2
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    Engineering method for aero-propulsive characteristics at hypersonic Mach numbers (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An engineering method has been developed for the rapid analysis of external aerodynamics and propulsive performance characteristics of airbreathing vehicles at hypersonic Mach numbers. This method, based on the theory of characteristics, has been developed to analyze fuselage-wing body combinations and body flaps with blunt or sharp leading/trailing edges. Arbitrary ratio of specific heat for the flowing medium can be specified in the program. Furthermore, the capability exists in the code to compute the inviscid inlet mass capture and momentum flux. The method is under development for computations of pressure distribution, and flow characteristics in the inlet, along with the effect of viscosity. Correlative studies have been performed for representative hypersonic configurations using the current method. The results of these correlations for various aerodynamics parameters are encouraging.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 91-5061
    Format: text
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  • 3
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    Test description and preliminary pitot-pressure surveys for Langley Test Technique Demonstrator at Mach 6 (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A propulsion/airframe integration experiment conducted in the NASA Langley 20-Inch Mach 6 Tunnel using a 16.8-in.-long version of the Langley Test Technique Demonstrator configuration with simulated scramjet propulsion is described. Schlieren and vapor screen visualization of the nozzle flow field is presented and correlated with pitot-pressure flow-field surveys. The data were obtained at nominal free-stream conditions of Re = 2.8 x 10 exp 6 and a nominal engine total pressure of 100 psia. It is concluded that pitot-pressure surveys coupled to schlieren and vapor-screen photographs, and oil flows have revealed flow features including vortices, free shear layers, and shock waves occurring in the model flow field.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: AIAA PAPER 92-3940
    Format: text
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  • 4
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    Mass flux similarity for slotted transonic-wind-tunnel walls (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A discussion of the flow field measurements obtained in the vertical plane at several stations along the centerline of slots in two different longitudinally slotted wind tunnel walls is presented. The longitudinal and transverse components of the data are then transformed using the concept of flow similarity to demonstrate the applicability of the technique to the development of the viscous shear flow along and through a slotted wall of an airfoil tunnel. Results are presented showing the performance of the similarity transformations with variations in tunnel station, Mach number, and airfoil induced curvature of the tunnel free stream.
    Keywords: AERODYNAMICS
    Type: NASA-TM-4281 , L-16864 , NAS 1.15:4281
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  • 5
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    Interactive application of quadratic expansion of chi-square statistic to nonlinear curve fitting (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This report contains a detailed theoretical description of an all-purpose, interactive curve-fitting routine that is based on P. R. Bevington's description of the quadratic expansion of the Chi-Square statistic. The method is implemented in the associated interactive, graphics-based computer program. Taylor's expansion of Chi-Square is first introduced, and justifications for retaining only the first term are presented. From the expansion, a set of n simultaneous linear equations is derived, then solved by matrix algebra. A brief description of the code is presented along with a limited number of changes that are required to customize the program of a particular task. To evaluate the performance of the method and the goodness of nonlinear curve fitting, two typical engineering problems are examined and the graphical and tabular output of each is discussed. A complete listing of the entire package is included as an appendix.
    Keywords: STATISTICS AND PROBABILITY
    Type: NASA-TM-4012 , L-16316 , NAS 1.15:4012
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  • 6
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    Theoretical and experimental analysis of the slotted-wall flow field in a transonic wind tunnel (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The flow in the vicinity of a longitudinally slotted wind-tunnel wall is theoretically analyzed, and equations describing the pressure drop across the wall are derived. The ideal form of the slotted-wall boundary condition is shown to effectively model the wall pressure drop upstream of the point of maximum model thickness providing that a zero-shift correction to the reference pressure is included in the analysis. The wall-pressure drop equations can be linearized by subtracting the tunnel-empty boundary condition. Good correlation is obtained between experimental and theoretical values for variations in Mach number and angle of attack.
    Keywords: AERODYNAMICS
    Type: SAE PAPER 871757
    Format: text
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  • 7
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    Implementation of the WICS Wall Interference Correction System at the National Transonic Facility (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Wall Interference Correction System (WICS) is operational at the National Transonic Facility (NTF) of NASA Langley Research Center (NASA LaRC) for semispan and full span tests in the solid wall (slots covered) configuration. The method is based on the wall pressure signature method for computing corrections to the measured parameters. It is an adaptation of the WICS code operational at the 12 ft pressure wind tunnel (12ft PWT) of NASA Ames Research Center (NASA ARC). This paper discusses the details of implementation of WICS at the NTF including tunnel calibration, code modifications for tunnel and support geometry, changes made for the NTF wall orifices layout, details of interfacing with the tunnel data processing system, and post-processing of results. Example results of applying WICS to a semispan test and a full span test are presented. Comparison with classical correction results and an analysis of uncertainty in the corrections are also given. As a special application of the code, the Mach number calibration data from a centerline pipe test was computed by WICS. Finally, future work for expanding the applicability of the code including online implementation is discussed.
    Keywords: Research and Support Facilities (Air)
    Type: AIAA Paper 2000-2383 , Measurement Technology and Ground Testing; Jun 19, 2000 - Jun 22, 2000; Denver, CO; United States
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  • 8
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    Numerical Study of the High-Speed Leg of a Wind Tunnel (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The paper describes the numerical study of the high-speed leg of the NASA Langley 14 by 22-foot Low Speed Wind Tunnel. The high-speed leg consists of the Settling Chamber, Contraction, Test Section, and First Diffuser. Results are shown comparing two different exit boundary conditions and two different methods of determining the surface geometry.
    Keywords: Fluid Mechanics and Thermodynamics; Numerical Analysis
    Type: NF1676L-18995 , AIAA Science and Technology Forum and Exposition; Jan 05, 2015 - Jan 09, 2015; Kissimmee, FL; United States
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  • 9
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    Air Density Measurements in a Mach 10 Wake Using Iodine Cordes Bands (2012)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: An exploratory study designed to examine the viability of making air density measurements in a Mach 10 flow using laser-induced fluorescence of the iodine Cordes bands is presented. Experiments are performed in the NASA Langley Research Center 31 in. Mach 10 air wind tunnel in the hypersonic near wake of a multipurpose crew vehicle model. To introduce iodine into the wake, a 0.5% iodine/nitrogen mixture is seeded using a pressure tap at the rear of the model. Air density was measured at 56 points along a 7 mm line and three stagnation pressures of 6.21, 8.62, and 10.0 MPa (900, 1250, and 1450 psi). Average results over time and space show rho(sub wake)/rho(sub freestream) of 0.145 plus or minus 0.010, independent of freestream air density. Average off-body results over time and space agree to better than 7.5% with computed densities from onbody pressure measurements. Densities measured during a single 60 s run at 10.0 MPa are time-dependent and steadily decrease by 15%. This decrease is attributed to model forebody heating by the flow.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: NF1676L-12551 , AIAA Journal; 50; 6; 1388-1397
    Format: text
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  • 10
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    Rayleigh Scattering Density Measurements, Cluster Theory, and Nucleation Calculations at Mach 10 (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In an exploratory investigation, quantitative unclustered laser Rayleigh scattering measurements of density were performed in the air in the NASA Langley Research Center's 31 in. Mach 10 wind tunnel. A review of 20 previous years of data in supersonic and Mach 6 hypersonic flows is presented where clustered signals typically overwhelmed molecular signals. A review of nucleation theory and accompanying nucleation calculations are also provided to interpret the current observed lack of clustering. Data were acquired at a fixed stagnation temperature near 990Kat five stagnation pressures spanning 2.41 to 10.0 MPa (350 to 1454 psi) using a pulsed argon fluoride excimer laser and double-intensified charge-coupled device camera. Data averaged over 371 images and 210 pixels along a 36.7mmline measured freestream densities that agree with computed isentropic-expansion densities to less than 2% and less than 6% at the highest and lowest densities, respectively. Cluster-free Mach 10 results are compared with previous clustered Mach 6 and condensation-free Mach 14 results. Evidence is presented indicating vibrationally excited oxygen and nitrogen molecules are absorbed as the clusters form, release their excess energy, and inhibit or possibly reverse the clustering process. Implications for delaying clustering and condensation onset in hypersonic and hypervelocity facilities are discussed.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: NF1676L-13000 , AIAA Journal; 50; 3; 698-707
    Format: application/pdf
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