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  • AERODYNAMICS  (5,058)
  • 1985-1989  (2,967)
  • 1980-1984  (2,091)
  • 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
    Format: text
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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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    Multidomain approach for calculating compressible flows (1982)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: A multidomain approach for calculating compressible flows by using unsteady or pseudo-unsteady methods is presented. This approach is based on a general technique of connecting together two domains in which hyperbolic systems (that may differ) are solved with the aid of compatibility relations associated with these systems. Some examples of this approach's application to calculating transonic flows in ideal fluids are shown, particularly the adjustment of shock waves. The approach is then applied to treating a shock/boundary layer interaction problem in a transonic channel.
    Keywords: AERODYNAMICS
    Type: NASA-TM-76692 , NAS 1.15:76692
    Format: application/pdf
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  • 5
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    Current developments lighter than air systems (1981)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Lighter than air aircraft (LTA) developments and research in the United States and other countries are reviewed. The emphasis in the U.S. is on VTOL airships capable of heavy lift, and on long endurance types for coastal maritime patrol. Design concepts include hybrids which combine heavier than air and LTA components and characteristics. Research programs are concentrated on aerodynamics, flight dynamics, and control of hybrid types.
    Keywords: AERODYNAMICS
    Type: NASA-TM-84744 , NAS 1.15:84744
    Format: application/pdf
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  • 6
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    Experimental investigation of the flow on the suction side of a thin Delta wing (1981)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Surface oil flow patterns were photographed and pressure distribution measurements were carried out on a sharp edged delta wing of aspect ratio lambda = 1.0 in order to determine the influence of Reynolds number and of vortex breakdown on the flow on the suction side of the wing. The formation of the secondary vortex occurs due to separation of a laminar boundary layer in the front part of the wing and due to separation of a turbulent boundary layer in the rear part of the wing. In the case of turbulent separation, the secondary separation line is closer to the wing leading edge than in the laminar case. The position of the transition depends on the Reynolds number and on the angle of incidence. The breakdown of a vortex above the wing leads to a kink in the secondary separation line.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75897
    Format: application/pdf
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  • 7
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    The influence of a high pressure gradient on unsteady velocity perturbations in the case of a turbulent supersonic flow (1980)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The amplification or reduction of unsteady velocity perturbations under the influence of strong flow acceleration or deceleration was studied. Supersonic flows with large velocity, pressure gradients, and the conditions in which the velocity fluctuations depend on the action of the average gradients of pressure and velocity rather than turbulence, are described. Results are analyzed statistically and interpreted as a return to laminar process. It is shown that this return to laminar implies negative values in the turbulence production terms for kinetic energy. A simple geometrical representation of the Reynolds stress production is given.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75236 , AAF-NT-79-10 , Colloq. d''Aerodynamique Appl.; Nov 07, 1978 - Nov 09, 1978; Marseille; France|Jul 01, 1979
    Format: application/pdf
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  • 8
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    Unsteady effects of a control surface in two dimensional subsonic and transonic flow (1980)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The experimental results of steady and unsteady pressure measurements, carried out in subsonic and transonic flow on a 16 percent relative thickness supercritical aerofoil, equipped with a trailing edge flap involving 25 percent of the chord, in a sinusoidal motion are given. These experimental results are compared with those obtained by various methods of steady and unsteady inviscid flow calculations. Some calculation results in which viscous effects have been taken into account, for both steady and unsteady flows, are also presented.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75775 , AGARD-CP-262
    Format: application/pdf
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  • 9
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    On the swelling of rolled up vortex surfaces and the breakdown of the vortex core for slender wings (1980)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Simplified models of the vortex distribution over cylindrical surfaces are developed. The effect of a change of vortex strength was analyzed quantitatively by menas of potential theory. The considerable bulging of the cylindrical vortex sheet as a consequence of the change of the vortex strength is discussed. The coiling-up of the vortices rotation in opposite directions over the cylindrical surface renders the condition for instability and the subsequent large spreading of the vortex core. These processes occur without a positive pressure gradient being necessary in the field of flow surrounding the coiled up vortex sheet.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75862
    Format: application/pdf
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  • 10
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    Investigations regarding the drag characteristics of flow-disturbing bodies which are arranged in line and attached to the wall (1980)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The flow characteristics of rectangular bodies mounted on the base area of a rectangular closed wind tunnel are investigated. As many as four bodies are mounted in line with equal distances between successive bodies. The Mach number of the flowing air is in the range from 0.1 to 0.5. Total and individual drag values could be charged within a wide range by a suitable selection of the distance between successive bodies.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75788
    Format: application/pdf
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