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  • AERODYNAMICS  (70)
  • FLUID MECHANICS AND HEAT TRANSFER  (63)
  • 1985-1989  (133)
  • 1980-1984
  • 1988  (133)
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  • 1985-1989  (133)
  • 1980-1984
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  • 1
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    Karhunen-Loeve expansion of Burgers' model of turbulence (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The properties of the Karhunen-Loeve expansion of a strongly inhomogeneous random process are examined with emphasis on applications to turbulent flow fields. The ability of the KL expansion to represent functions that have both slow and rapid variations in a relatively small number of expansion terms is tested on a one-dimensional model based on the forced Burgers' equation. The rate of the convergence of the expansion is evaluated, and its dependence on the Reynolds number is determined. It is shown that the KL eigenfunctions possess wall boundary layers attached to outer structures that are independent of the Reynolds number (at high Reynolds numbers). It is also shown that the spectrum of eigenvalues is broad at large Reynolds numbers, requiring many terms to represent higher-order derivatives of the function.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physics of Fluids (ISSN 0031-9171); 31; 2573-258
    Format: text
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  • 2
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    Sensitivity of mixing layers to three-dimensional forcing (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: It is well known that turbulent mixing layers are dominated by large scale, fairly coherent structures, and that these structures are related to the stability characteristics of the flow. These facts have led researchers to attempt controlling such flows by selectively forcing certain unstable modes, which can in addition have the effect of suppressing other modes. Much of the work on controlling the mixing layer has relied on forcing 2-D instabilities. The results of forcing 3-D instabilities are addressed. The objectives of the work are twofold: to understand how a mixing layer responds to 3-D perturbations, and to test the validity of an amplitude expansion in predicting the mixing layer development. The amplitude expansion could be very useful in understanding and predicting the 3-D response of the flow to a variety of initial conditions.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Stanford Univ., Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program; p 91-116
    Format: application/pdf
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  • 3
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    Transition prediction in external flows via linear stability theory (1988)
    In:  Other Sources
    Details
    Publication Date: 2018-12-01
    Description: Linear stability theory results are presented for flight and low-disturbance wind tunnels, at low and high speeds, and for T-S, Gortler, and cross-flow modes. Results show that, in the absence of Morkovin 'bypasses', transition at low background disturbance levels corresponds to N-factors of the order of 9 to 11, provided that phenomena such as curvature effects are included. The results point to a wider range of applicability for the e exp N method than previously conjectured, and suggest that the e exp N method can be used to parametrize transition predictions as a function of parameters which affect the mean flow profiles for such purposes as LFC and minimum drag design.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 4
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    Flutter analysis of highly swept delta wings by conventional methods (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The flutter boundaries of six thin highly-swept delta-platform wings have been calculated. Comparisons are made between experimental data and results using several aerodynamic methods. The aerodynamic methods used include a subsonic and supersonic kernel function, second order piston theory, and a transonic small disturbance code. The dynamic equations of motion are solved using analytically calculated mode shapes and frequencies.
    Keywords: AERODYNAMICS
    Type: NASA-TM-101530 , NAS 1.15:101530
    Format: application/pdf
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  • 5
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    Radiation heat transfer in the wake of a hypersonic vehicle (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Radiation heat transfer (RHT) from the wake of a hypersonic vehicle to its afterbody is evaluated from Gnoffo and Greene's (1987) calculated wake flowfield and the radiative properties of ionized high-temperature air with the calculated nonequilibrium composition. The 4.2-m aeroassisted flight experiment at an altitude of 75 km and velocity of 8900 m/s causes a 0.1-m-thick layer initially at T = 10,000 K and P = 1 kN/sq m to separate from the shoulder of the forebody heat shield and spread aft to form a wake at approximately T = 5000 K and P = 20 N/sq m. Gas in the separated flow region at approximately T = 3000 K and P = 10 N/sq m, recirculates about the afterbody. It is shown that the radiating layer, recirculating gases, and wake are optically thin for purposes of making engineering RHT calculations. Directional, spectral, and spatial variations of the radiation incident upon the afterbody are presented.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 88-2634
    Format: text
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  • 6
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    Unsteady shock-induced turbulent separation in Mach 5 cylinder interactions (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Wall pressure fluctuations have been determined under the unsteady separation shock in interactions generated by unswept circular cylinders, using a nominal freestream Mach number of 5 and a freestream unit Reynolds number of 53 x 10 to the 6th/m. The distributions of shock frequency and period were calculated using a conditional sampling algorithm. The shock frequency distributions were all found to be broadband, with frequencies being typically 1-2 kHz. The results support the previous suggestion that pressure fluctuations in the separated flow drive the shock motion.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 88-0305
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  • 7
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    Potential applications of computational fluid dynamics to biofluid analysis (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Computational fluid dynamics was developed to the stage where it has become an indispensable part of aerospace research and design. In view of advances made in aerospace applications, the computational approach can be used for biofluid mechanics research. Several flow simulation methods developed for aerospace problems are briefly discussed for potential applications to biofluids, especially to blood flow analysis.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-100089 , A-88126 , NAS 1.15:100089
    Format: application/pdf
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  • 8
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    The NASA Langley Laminar-Flow-Control (LFC) experiment on a swept, supercritical airfoil: Design overview (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A large-chord, swept, supercritical, laminar-flow-control (LFC) airfoil was designed and constructed and is currently undergoing tests in the Langley 8 ft Transonic Pressure Tunnel. The experiment was directed toward evaluating the compatibility of LFC and supercritical airfoils, validating prediction techniques, and generating a data base for future transport airfoil design as part of NASA's ongoing research program to significantly reduce drag and increase aircraft efficiency. Unique features of the airfoil included a high design Mach number with shock free flow and boundary layer control by suction. Special requirements for the experiment included modifications to the wind tunnel to achieve the necessary flow quality and contouring of the test section walls to simulate free air flow about a swept model at transonic speeds. Design of the airfoil with a slotted suction surface, the suction system, and modifications to the tunnel to meet test requirements are discussed.
    Keywords: AERODYNAMICS
    Type: NASA-TP-2809 , L-16324 , NAS 1.60:2809
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  • 9
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    Navier-Stokes calculations using Cartesian grids. I - Laminar flows (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A finite-volume formulation for the Navier-Stokes equations using Cartesian grids is used to study flows past airfoils. In addition to the solution of the complete equations, solutions for two simplified versions of the governing equations were obtained and compared with those using body-fitted grids. Results are presented for two airfoil sections, NACA 0012 and RAE 2822, for a range of Mach numbers, angles of attack, and Reynolds numbers. It is shown that the results are highly dependent on the smoothness of the surface grid. Without such smoothness, the skin friction and pressure converge to nonuniform distributions. On the other hand, when surface cells with smoothly varying areas are used, the results compared favorably with calculations employing body-fitted grids.
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 26; 1181-118
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  • 10
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    Computational validation of a parabolized Navier-Stokes solver on a sharp-nose cone at hypersonic speeds (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Perfect gas computational results from a newly-developed upwind, parabolized Navier-Stokes (PNS) solver are compared with an existing set of experimental laminar results for a 10-deg half-angle circular cone at freestream Mach number of 7.95. Comparisons were performed with surface pressure and heat transfer data, as well as with flowfield pitot measurements. The PNS code predicted the surface quantities accurately up through 20-deg angle-of-attack, including crossflow separation, and correctly defined the location of the bow shock and the edge of the boundary layer. The importance of cell Reynolds number, grid density, and thermal boundary conditions to the accurate prediction of the flowfield are examined through numerical emamples.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 88-2566 , AIAA Applied Aerodynamics Conference; Jun 06, 1988 - Jun 08, 1988; Williamsburg, VA; United States
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