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  • Inorganic Chemistry  (7,178)
  • AERODYNAMICS  (5,077)
  • 1985-1989  (6,382)
  • 1975-1979  (5,873)
Collection
Keywords
Publisher
Years
Year
  • 1
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    Application of a semianalytical technique for sensitivity analysis of unsteady aerodynamic computations (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: A semianalytical approach is developed for the sensitivity analysis of linear unsteady aerodynamic loads. The semianalytical approach is easier to implement than the analytical approach. It is also computationally less expensive than the finite difference approach when used with panel methods which require a large number of panels. The semianalytical approach is applied to an isolated airfoil in a two-dimensional flow and rotating propfan blades in three-dimensional flow. Sensitivity coefficients with respect to nonshape-dependent variables are shown for some cases.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 88-2377 , Structures, Structural Dynamics and Materials Conference; Apr 18, 1988 - Apr 20, 1988; Williamsburg, VA; United States
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  • 2
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    Some numerical calculations by using linear classical sonic theories approached from sub- or supersonic speeds (1987)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The unsteady aerodynamics of a two-dimensional wing at sonic speed are studied by using so-called classical sonic theories (linear), approached from supersonic flow (M=1+0) or subsonic flow (M=1-0). In the former approach, the exact expressions of lift and lift distribution are obtained in terms of Fresnel integrals, while in the latter approach an integral equation must be solved, the kernel function of which is obtained from the subsonic Possio's equation and has a root singularity. The discrete analysis is adopted on the basis of the semicircle method (SCM) and the weighting function for subsonic-flow-Gauss-quadrature, as well as modified characteristics obtained from both approaches agree quite well with each other. The results obtained by the present computations are compared with those of DLM-C (subsonic 2D code) developed by ANDO et al, and are found to give a reasonable outer boundary for subsonic unsteady aerodynamics.
    Keywords: AERODYNAMICS
    Type: NASA-TT-20112 , NAS 1.77:20112
    Format: text
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  • 3
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    The Aerodynamic Optimization of Wings at Subsonic Speeds and the Influence of Wingtip Design (1987)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Some of the objectives of modern aircraft development are related to the achievement of reduced fuel consumption and aircraft noise. This investigation is mainly concerned with the aerodynamic aspects of aircraft development, i.e., reduction of induced drag. New studies of wing design, and in particular wing tips, are considered. Induced drag is important since, in cruising flight, it accounts for approximately one-third of the entire drag for the aircraft, and one-half while climbing. A survey is presented for the wing geometries and wing tip designs studied, and theoretical investigations of different planar wings with systematically varied wing tip forms are conducted. Attention is also paid to a theoretical study of some planar and nonplanar wings and their comparison with experimental data.
    Keywords: AERODYNAMICS
    Type: NASA-TM-88534 , NAS 1.15:88534
    Format: application/pdf
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  • 4
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    On wings of circular design (1979)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Prandtl's method of sources and sinks for air foils is used to investigate the aerodynamics of circular wings in constant flow. Lift distribution, total lift, and pitching moment are investigated as well as the influence of changes in the angle of attack.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75505
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  • 5
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    Solution of a few nonlinear problems in aerodynamics by the finite elements and functional least squares methods (1979)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The numerical simulation of the transonic flows of idealized fluids and of incompressible viscous fluids, by the nonlinear least squares methods is presented. The nonlinear equations, the boundary conditions, and the various constraints controlling the two types of flow are described. The standard iterative methods for solving a quasi elliptical nonlinear equation with partial derivatives are reviewed with emphasis placed on two examples: the fixed point method applied to the Gelder functional in the case of compressible subsonic flows and the Newton method used in the technique of decomposition of the lifting potential. The new abstract least squares method is discussed. It consists of substituting the nonlinear equation by a problem of minimization in a H to the minus 1 type Sobolev functional space.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75732
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  • 6
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    Aeronautical engineering: A continuing bibliography with indexes (supplement 225) (1988)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: This bibliography lists 429 reports, articles, and other documents introduced into the NASA scientific and technical information system in March, 1988.
    Keywords: AERODYNAMICS
    Type: NASA-SP-7037(225) , NAS 1.21:7037(225)
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  • 7
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    Finite element calculations for aerodynamic coefficients of a 3-dimensional body in subsonic flow using Green's function method (1988)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: An accurate method for evaluating the derivatives along circular paths on the surface is proposed. Calculations are made on various practical configurations such as wing-body combinations, tandem wings, wings with dihedral angles at sideslip, ground effects, interference between a sphere and wind tunnel, etc. Comparisons with experiment show good agreement.
    Keywords: AERODYNAMICS
    Type: NASA-TT-20208 , NAS 1.77:20208
    Format: text
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  • 8
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    Calculation of non-stationary aerodynamic forces in the near sonic range (1988)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The development of a mathematical method for calculating nonstationary supersonic flow in the near-sonic range is described. A perturbation formula is derived based on the exact stationary values; it is applicable to the equation for potential. The problem can thus be divided into stationary and nonstationary fields. The pressure distribution in an oscillating profile is determined, based on hyperbolic differential equations. It is shown that there are important corollaries concerning the application of linear theory. With suitable extrapolations, linear theory can be used up to about Mach 0.8. Linear theory is not applicable, however, when determining the moment coefficients; for this case, a special technique is described.
    Keywords: AERODYNAMICS
    Type: NASA-TT-20310 , NAS 1.77:20310
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  • 9
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    Aeronautical engineering: A continuing bibliography with indexes (supplement 219) (1987)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: This bibliography lists 586 reports, articles, and other documents introduced into the NASA scientific and technical information system in October, 1987.
    Keywords: AERODYNAMICS
    Type: NASA-SP-7037(219) , NAS 1.21:7037(219)
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  • 10
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    Calculation of aerodynamic heat transfer for blunt-nosed thin wings at different angles of attack at supersonic speeds (1987)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: A method for calculating aerodynamic heat transfer on thin wings at angles of attack is provided, based on the assumption of small cross flow and the calculation of an infinite cylinder. It is valid in the range of supersonic and hypersonic speeds. The method does not require calculation of the details of the stream lines and can be used for various swept wings at moderate angle of attack or yaw angle. A comparison between theoretical and experimental results is given.
    Keywords: AERODYNAMICS
    Type: NASA-TT-20127 , NAS 1.77:20127
    Format: text
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  • 11
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    Aircraft icing: Introduction (1979)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The objectives of the Workshop were as follows: (1) to assess the current understanding of fixed wing and rotorcraft operational icing environments and problems (2) to evaluate facilities requirements for R&D and certification purposes (3) to examine means of improving icing forecasts (4) to identify shortcomings in aeronautical icing knowledge which can be alleviated by new research and instrumentation development.
    Keywords: AERODYNAMICS
    Type: NASA. Lewis Res. Center Aircraft Icing; 3 p
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  • 12
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    Practical calculation of laminar and turbulent bled-off boundary layers (1978)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Bleed-off of boundary layer material is shown to be an effective means for reducing drag by conserving the laminar boundary layer and preventing separation of the turbulent boundary layer. The case in which the two effects of bleed-off overlap is examined. Empirical methods are extended to the case of bleed-off. Laminar and turbulent boundary layers are treated simultaneously and the approximation differential equations are solved without an uncertain error. The case without bleed-off is also treated.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75328
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  • 13
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    Effect of the properties of a porous coating on boundary layer stability (1978)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Drawing off gas from the boundary layer is a well-known method for increasing the stability of boundary layers. The increase in stability is primarily connected with a change in the velocity profile form in the case of suction. On the basis of the assumption that the velocity perturbations on a porous slate do not equal zero, the influence of the properties of a permeable surface upon the boundary layer stability were studied.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75235
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  • 14
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    Experimental studies on the influence of the degree of turbulence and of a turbulence thread on the compressible subsonic flow through flat compressor cascades (1978)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The measurements revealed that at low Reynolds numbers the profile loss is considerably reduced both by the increased degree of turbulence and by a turbulence thread, while it is somewhat increased at high Reynolds numbers, and that a profile loss reduction is connected with an increase in deflection and in pressure shift. The turbulence generator is most effective on the one hand in the middle of the operating range of the cascades, and on the other at very high Mach numbers together with a large angle of incidence.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75276
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  • 15
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    A finite volume method for calculating transonic potential flow around wings from the pressure minimum integral (1978)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Analysis of the pressure minimum integral in the calculation of three-dimensional potential flow around wings makes it possible to use non-rectangular mesh networks for distributing the three-dimensional potential into discrete points. The method is comparatively easily expanded to the treatment of realistic airplane configurations. Shock-pressure affected pressure distributions on any wings are determined with accuracy using this method.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75324
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  • 16
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    Measurement of the turbulence intensity behind a two-dimensional cascade and in a three-stage axial blower (1978)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Turbulence intensity (Tu) measurements were made in two-dimensional and rotating cascades of blades in a low-speed cascade wind tunnel using hot-wire probes as sensors. The local Tu at Re = 1.6x100000 was determined in the wake zone behind a two-dimensional cascade. Then the values were recomputed for a rotating cascade, giving a mean turbulence intensity of 6.5% at 1/10 chord downstream and 2.9% at one chord. Fans were used for measurements on the rotating cascade. Re was equal to 7x100000. Frequency analysis was employed to separate the actual Tu of the entry flow from the effects caused by interaction with the rotor blades, showing that the true Tu increased from a few tenths of a percent to 6.6% in the 1st rotor, and from 7.2 to 9.3% in the 2d rotor. The Tu behind the 3d rotor was equal to 8.9%.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75275
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  • 17
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    Methods and results of boundary layer measurements on a glider (1978)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Boundary layer measurements were carried out on a glider under natural conditions. Two effects are investigated: the effect of inconstancy of the development of static pressure within the boundary layer and the effect of the negative pressure difference in a sublaminar boundary layer. The results obtained by means of an ion probe in parallel connection confirm those results obtained by means of a pressure probe. Additional effects which have occurred during these measurements are briefly dealt with.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75294
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  • 18
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    Summary of experimentally determined facts concerning the behavior of the boundary layer and performance of boundary layer measurements (1978)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: A summary report of boundary layer studies is presented. Preliminary results of experimental measurements show that: (1) A very thin layer (approximately 0.4 mm) of the boundary layer seems to be accelerated; (2) the static pressure of the outer flow does not remain exactly constant through the boundary layer; and (3) an oncoming boundary layer which is already turbulent at the suction point can again become laminar behind this point without being completely sucked off.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75270
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  • 19
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    Airfoil profile in a nonuniform flow (1978)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: A theory of airfoil section past two dimensional nonuniform flow is developed. The theory is based on representation of airfoil section by vortex and source distributions and it can be used for calculation of aircraft wings in homogeneous and inhomogeneous flow, as well as for calculation of straight and radial blade and vane-cascades.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75272
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  • 20
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    Transonic flow past an airfoil with condensation (1978)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: In connection with investigations conducted to determine the influence of water vapor on experiments in wind tunnels, the question arose as to what changes due to vapor condensation might be expected in airfoil measurements. Density measurements on circular-arc airfoils aided by an interferometer in choked tunnels with parallel walls show that increasing humidity produces increasing changes in the flow field. The flow becomes nonstationary at high humidity. At the airfoil, however, the influence of the condensation is only felt, inasmuch as the shock bounding the local supersonic region moves upstream with increasing humidity while its intensity decreases. The density distribution upstream of the shock remains unchanged. Even if the flow becomes nonstationary in the vicinity of the airfoil, no changes occur at the airfoil.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75201
    Format: application/pdf
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