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  • AERODYNAMICS  (5,077)
  • 1985-1989  (2,967)
  • 1975-1979  (2,110)
  • 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
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    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
    Format: application/pdf
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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
    Format: application/pdf
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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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