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  • AERODYNAMICS  (299)
  • 2015-2019
  • 2005-2009
  • 1975-1979
  • 1970-1974  (299)
  • 1950-1954
  • 1974  (299)
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  • 2015-2019
  • 2005-2009
  • 1975-1979
  • 1970-1974  (299)
  • 1950-1954
Year
  • 1
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    Lifting-surface theory for a semi-infinite wing in oblique gust (1974)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: An unsteady lifting-surface theory is developed for the calculation of the airload on a semi-infinite-span thin wing in a compressible flow due to interaction with an oblique gust. By using the solutions obtained for a two-dimensional wing, the problem is formulated so that the unknown is taken to be the difference between the airload on the semi-infinite wing and that on a two-dimensional wing under the same gust conditions. Since this airload difference is nonzero only near the wing tip, the control points need be distributed in the tip region only; this significantly simplifies the numerical procedure. Results are presented for a wing with rectangular tip. The implication for noise and unsteady loads due to blade-vortex interaction for helicopter rotors is discussed.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 12; Dec. 197
    Format: text
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  • 2
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    Planetary entry aerothermodynamics. II - Computational analyses and flight experience (1974)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Limitations concerning the possibility to simulate all the significant flow and thermal phenomena occurring during the entry of a space vehicle into a planetary atmosphere make it necessary to rely on computational analyses to obtain the required data for the design of the spacecraft needed for the NASA missions planned for the next two decades. 'Benchmark' computer programs concerned with complete, detailed, and accurate computational solutions of entry problems are considered along with programs representing engineering approximations for cases in which the accuracy provided by the benchmark programs is not needed. The information obtainable by computational analysis has to be supplemented by actual flight experience in order to meet the goals of the NASA entry-technology program. The individual space missions planned for the coming years are examined together with the possibilities for obtaining the data needed to satisfy the entry requirements in each case.
    Keywords: AERODYNAMICS
    Type: Astronautics and Aeronautics; 12; Dec. 197
    Format: text
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  • 3
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    Analysis of acoustic radiation in a jet flow environment (1974)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: The analysis of sound fields from arbitrary source distributions in terms of Legendre and spherical Hankel functions is well known. The purpose of this paper is to extend this classical method of analysis to environments such as jet flows where flow and flow gradients are inherently present. The wave-equation governing the radiation of sound in such an environment is derived. The steady state flow and flow gradients in the axial and transverse directions appear as coefficients in the terms of the wave-equation. A semi-numerical method is used to solve the wave-equation in terms of modified spherical harmonics yielding the phase velocities and the directivities of an infinite set of modes. The directivity of each mode is obtained in terms of modified Legendre functions by numerical integration. Some results of these directivity and phase-velocity calculations are presented for a limited number of frequency and flow parameters. Both convective and shear refraction are shown to be important.
    Keywords: AERODYNAMICS
    Type: Journal of Sound and Vibration; 36; Sept. 8
    Format: text
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  • 4
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    Unified approach to aerodynamic sound generation in the presence of solid boundaries (1974)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: A general equation governing aerodynamic sound generation in the presence of solid boundaries is derived. It is shown that all the theories in the literature appear as special cases of this general equation. Derived special equations for propeller and fan noise are likewise shown to be more general than the conventional equations in that they make allowance for variation in retarded time over the blade surfaces.
    Keywords: AERODYNAMICS
    Type: Acoustical Society of America; vol. 56
    Format: text
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  • 5
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    Automatic numerical generation of body-fitted curvilinear coordinate system for field containing any number of arbitrary two-dimensional bodies (1974)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: A method for automatic numerical generation of a general curvilinear coordinate system with coordinate lines coincident with all boundaries of a general multi-connected region containing any number of arbitrarily shaped bodies is presented. With this procedure the numerical solution of a partial differential system may be done on a fixed rectangular field with a square mesh with no interpolation required regardless of the shape of the physical boundaries, regardless of the spacing of the curvilinear coordinate lines in the physical field, and regardless of the movement of the coordinate system. Numerical solutions for the lifting and nonlifting potential flow about Joukowski and Karman-Trefftz airfoils using this coordinate system generation show excellent comparison with the analytic solutions. The application to fields with multiple bodies is illustrated by a potential flow solution for multiple airfoils.
    Keywords: AERODYNAMICS
    Type: Journal of Computational Physics; 15; July 197
    Format: text
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  • 6
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    Analysis of propagation of waves of acoustic frequencies in curved ducts (1974)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: The propagation of waves of acoustic frequencies in curved ducts of rectangular cross section is studied for the first four modes. The analysis makes use of Bessel functions of the order (n + 1/2) to construct curves of wavenumber in the duct versus imposed wavenumber and to determine the profile of vibrational velocities. A wide range of duct widths and unrestricted radii of curvature have been considered. The characteristics of motion in a bend are compared with propagation of waves in a straight duct, and important differences in the behavior of waves are noted.
    Keywords: AERODYNAMICS
    Type: Acoustical Society of America; vol. 56
    Format: text
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  • 7
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    Axial flow measurements in trailing vortices (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A scanning laser Doppler velocimeter was used to measure the axial velocity defect in the cores of trailing vortices behind a lifting airfoil of rectangular planform. Data were obtained at several different angles of attack and downstream distances ranging from 30 to 1000 chord lengths. The test was designed to obtain continuous data from the near field into the far field while removing uncertainties associated with the interpretation of data obtained by the hydrogen bubble technique. The measured velocities of V sub x/U sub infinity are compared with those predicted. The agreement is remarkably good over the entire range of downstream distances, which supports the credibility of calculating axial velocities using the results of Moore and Saffman (1973).
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 12; Aug. 197
    Format: text
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  • 8
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    Vortex measurements behind a swept wing transport model (1974)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: A backscatter laser Doppler velocimeter which simultaneously senses the axial and the tangential components of the velocity has been used to measure the velocity distributions in the near wake of a swept wing semispan transport model in a wind tunnel. The model configuration included nacelles, pylons, antishock bodies, and wing flaps which could be deflected 27 deg. Typical wake vortex velocity profiles are presented for the flaps-retracted and the flaps-deployed 27 deg configurations, respectively.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 11; June 197
    Format: text
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  • 9
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    Shock shapes of blunt bodies in hypersonic helium, air, and CO2 flows (1974)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: A primary factor governing hypersonic flowfield characteristics of blunt vehicles entering planetary atmospheres is the normal shock density ratio. Hence, a means of duplicating or simulating the high density ratios experienced during planetary entry is needed. One facility having the capability of generating a range of hypersonic-hypervelocity flow conditions in arbitrary test gases is the expansion tube. Preliminary shock shape results obtained in the Langley 6-in. expansion tube at hypersonic conditions are presented. Normal shock density ratios from approximately 4 to 19 were generated using helium, air, and CO2 test gases at freestream velocities from 5 to 7 km/sec. Test models were a flat-faced cylinder and the Viking aeroshell.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 12; Mar. 197
    Format: text
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  • 10
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    Computation of transonic flow about lifting wing-cylinder combinations (1974)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Some results are described for a lifting rectangular wing centrally located on a circular-cylindrical body. This simple configuration has been utilized in order to assess the merits of a mapping technique for wing-body configurations. The procedure employed makes use of a coordinate transformation to simplify specification of the surface boundary condition in the computation of the flow about the wing. The method can be extended to incorporate wing sweep, finite length body of noncircular cross section, and arbitrary wing placement; however, these extensions involve a considerable increase in complexity of the problem.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 11; Apr. 197
    Format: text
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