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  • 1975-1979  (9)
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  • 1
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    Turbulent plane Couette flow using probability distribution functions (1977)
    American Institute of Physics
    Details
    Publication Date: 1977-01-01
    Print ISSN: 0031-9171
    Topics: Physics
    Published by American Institute of Physics
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    PAPER CURRENT
  • 2
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    Prospects for computational aerodynamics (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The integral representations approach, for the solution of the Navier-Stokes equations is discussed as well as experience in its development and in applying available finite-difference and finite-element techniques to the treatment of three-dimensional problems, and the computation of turbulent flow. The magnitude of efforts required to develop turbulence models and three-dimensional algorithms indicates that the computational fluid dynamics research must have a broad base. Broader access to modern computing facilities that are in existence within NASA should be promoted for active researchers not directly affiliated with that agency.
    Keywords: AERODYNAMICS
    Type: NASA. Ames Res. Center Future Computer Requirements for Computational Aerodynamics; p 221-227
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    A study of turbulent flow between parallel plates by a statistical method (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Turbulent Couette flow between parallel plates was studied from a statistical mechanics approach utilizing a model equation, similar to the Boltzmann equation of kinetic theory, which was proposed by Lundgren from the velocity distribution of fluid elements. Solutions to this equation are obtained numerically, employing the discrete ordinate method and finite differences. Two types of boundary conditions on the distribution function are considered, and the results of the calculations are compared to available experimental data. The research establishes that Lundgren's equation provides a very good description of turbulence for the flow situation considered and that it offers an analytical tool for further study of more complex turbulent flows. The present work also indicates that modelling of the boundary conditions is an area where further study is required.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-2663
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Study of viscous flow about airfoils by the integro-differential method (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An integro-differential method was used for numerically solving unsteady incompressible viscous flow problems. A computer program was prepared to solve the problem of an impulsively started 9% thick symmetric Joukowski airfoil at an angle of attack of 15 deg and a Reynolds number of 1000. Some of the results obtained for this problem were discussed and compared with related work completed previously. Two numerical procedures were used, an Alternating Direction Implicit (ADI) method and a Successive Line Relaxation (SLR) method. Generally, the ADI solution agrees well with the SLR solution and with previous results are stations away from the trailing edge. At the trailing edge station, the ADI solution differs substantially from previous results, while the vorticity profiles obtained from the SLR method there are in good qualitative agreement with previous results.
    Keywords: AERODYNAMICS
    Type: NASA-CR-145693
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Optimum performance and potential flow field of hovering rotors (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Rotor and propeller performance and induced potential flowfields were studied on the basis of a rotating actuator disk concept, with special emphasis on rotors hovering out of ground effect. A new theory for the optimum performance of rotors hovering OGE is developed and presented. An extended theory for the optimum performance of rotors and propellers in axial motion is also presented. Numerical results are presented for the optimum distributions of blade-bound circulation together with axial inflow and ultimate wake velocities for the hovering rotor over the range of thrust coefficient of interest in rotorcraft applications. Shapes of the stream tubes and of the velocities in the slipstream are obtained, using available methods, for optimum and off-optimum circulation distributions for rotors hovering in and out of ground effect. A number of explicit formulae useful in computing rotor and propeller induced flows are presented for stream functions and velocities due to distributions of circular vortices over axi-symmetric surfaces.
    Keywords: AERODYNAMICS
    Type: NASA-CR-137705
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Turbulent plane Couette flow using probability distribution functions (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A numerical scheme employing a combination of the discrete ordinate method and finite differences is developed for solving the one-dimensional form of Lundgren's (1967) model equation for turbulent plane Couette flow. The approach used requires no a priori assumption about the form of the turbulent distribution function, and the numerical solution is obtained directly from the governing differential equations. Two different types of boundary conditions (zero-gradient and Chapman-Enskog) for the distribution function are evaluated by comparing the numerical results with experimental data. It is found that: (1) the present approach gives convergent and stable results over a wide range of Reynolds numbers; (2) Lundgren's equation yields results that compare well with experimental data for mean velocity and skin friction in the case of simple Couette flow; (3) the zero-gradient boundary condition leads to a logarithmic flow profile; and (4) the Chapman-Enskog boundary condition provides very good agreement with experimental data when applied within the near-wall region.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physics of Fluids; 20; Apr. 197
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    A numerical study of viscous flow around an airfoil (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: An integrodifferential method, previously formulated in terms of velocity and vorticity vectors, is reformulated in terms of stream function and vorticity for two-dimensional incompressible viscous flows. The reformulated integrodifferential method is shown to retain the distinguishing feature of the previous formulation in permitting the confinement of the solution field to the viscous region of the flow and consequently offers great computational advantages. The application of this procedure in a study of an incompressible flow around an impulsively started 9% thick symmetric Joukowski airfoil at an angle of attack of 15 deg and a Reynolds number of 1000 is discussed. Numerical results are presented and compared with available finite-difference results.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 76-337 , Fluid and Plasma Dynamics Conference; Jul 14, 1976 - Jul 16, 1976; San Diego, CA
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    A flowfield segmentation method for the numerical solution of viscous flow problems (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: International Conference on Numerical Methods in Fluid Dynamics; Jun 24, 1974 - Jun 28, 1974; Boulder, CO
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    Velocity and extraneous boundary conditions of viscous flow problems (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A novel method for treating certain troublesome boundary conditions in the numerical solution of time-dependent incompressible viscous flow problems is presented. This new method is developed on the basis of an integral representation for the velocity vector which contains the entire kinematics of the problem, including the boundary conditions of concern. It is shown that for the exterior flow problem the free-stream condition is satisfied at infinity exactly and the need to treat a far-field condition is removed by the use of the integral representation. The distribution of a nonvelocity variable on the solid boundary - i.e., the 'extraneous' boundary condition needed for both the exterior and the interior flows - is shown to be governed by the kinematics of the problem.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 75-47 , American Institute of Aeronautics and Astronautics, Aerospace Sciences Meeting; Jan 20, 1975 - Jan 22, 1975; Pasadena, CA
    Format: text
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