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  • 1
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    Infrared limb-darkening effects for the earth-atmosphere system (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: GEOPHYSICS
    Type: AIAA Journal (ISSN 0001-1452); 23; 405-409
    Format: text
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  • 2
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    Investigation of viscous/inviscid interaction in transonic flow over airfoils with suction (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The viscous/inviscid interaction over transonic airfoils with and without suction is studied. The streamline angle at the edge of the boundary layer is used to couple the viscous and inviscid flows. The potential flow equations are solved for the inviscid flow field. In the shock region, the Euler equations are solved using the method of integral relations. For this, the potential flow solution is used as the initial and boundary conditions. An integral method is used to solve the laminar boundary-layer equations. Since both methods are integral methods, a continuous interaction is allowed between the outer inviscid flow region and the inner viscous flow region. To avoid the Goldstein singularity near the separation point the laminar boundary-layer equations are derived in an inverse form to obtain solution for the flows with small separations. The displacement thickness distribution is specified instead of the usual pressure distribution to solve the boundry-layer equations. The Euler equations are solved for the inviscid flow using the finite volume technique and the coupling is achieved by a surface transpiration model. A method is developed to apply a minimum amount of suction that is required to have an attached flow on the airfoil. The turbulent boundary layer equations are derived using the bi-logarithmic wall law for mass transfer. The results are found to be in good agreement with available experimental data and with the results of other computational methods.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-183112 , NAS 1.26:183112 , ODU/ICAM-88-101
    Format: application/pdf
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  • 3
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    Suction laminarization of highly swept supersonic laminar flow control wings (1988)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An evaluation is made of a suction-based method for the laminarization of highly-swept supersonic wings at cruise Mach numbers in the 2.0-2.5 range, in the interest of the reduction of wave drag due to lift. The laminar boundary layer development, as well as Tollmien-Schlichting and crossflow instabilities, have been analyzed for the case of an X66 supercritical airfoil at 60 and 72 deg sweep, for Mach numbers of 1.56 and 2.52, respectively. Strong suction is found to be needed at the front part of the upper surface and both the upper and lower rear pressure-rise areas.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 88-4471
    Format: text
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  • 4
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    Infrared limb-darkening effects for the earth-atmosphere system (1983)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An infrared radiative transfer model has been developed for evaluating anisotropic functions in the longwave region (5-50 microns) due to limb-darkening effects in the earth's atmosphere. An accurate narrow-band model of absorption has been used for computing transmission functions of the atmosphere. Absorption due to all major and minor atmospheric constituents has been taken into account including the continuum absorption due to water vapor. Anisotropic functions have been calculated for several latitudinal and seasonal climatological-average model atmospheres. The effects of the variability of various meteorological parameters, e.g. surface temperature, surface relative humidity, and cloud-top height have been examined. It has been found that the variability of cloud parameters has the largest effect on the infrared anisotropic functions.
    Keywords: GEOPHYSICS
    Type: AIAA PAPER 83-0161
    Format: text
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  • 5
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    Hybrid approach to steady transonic normal shock-compressible laminar boundary layer interactions over airfoils with suction (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Transonic airfoil flow is to a large degree affected by viscous-inviscid interactions. Among them a key role is played by the boundary layer interaction with the shock wave embedded in the flow field and the interaction of the boundary layer with the sustained adverse pressure gradients. The effects of these interactions can be controlled or suppressed by introducing surface mass transfer such as suction. This investigation deals strictly with the study of shock-laminar boundary layer interactions including distributed mass transfer. The present calculations agree with experiments on a swept LFC wing at low speeds which indicates that with a suitable choice of the extent of the airfoil surface over which suction is applied and adjustment of the suction velocity, full-chord laminar flow can be maintained and separation can be prevented completely.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 85-0522
    Format: text
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  • 6
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    Blunt-nosed swept supercritical LFC wings without nose flaps (1990)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: To simplify the design of swept supercritical (SC) Laminar Flow Control (LFC) wings and maintain satisfactory low speed characteristics, blunt-nosed swept SC LFC wings without nose flaps and lower wing loadings were studied. Their boundary layer crossflow in the leading edge area is optimally controlled (1) by compensating the boundary layer crossflow of the front acceleration zone by an opposite crossflow in a downstream pressure rise area, (2) by maintaining a neutrally stable boundary layer crossflow by suction within a narrow spanwise suction strip located close to the wing attachment line in the front acceleration zone. The required suction massflow and power are then very small, especially considering the strongly stabilizing effect of surface and streamline curvature on crossflow stability.
    Keywords: AERODYNAMICS
    Type: IUTAM Symposium on Laminar-Turbulent Transition; Sept. 11-15, 1989; Toulouse; France
    Format: text
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  • 7
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    Design aspects of long range supersonic LFC airplanes with highly swept wings (1990)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: Studies on supersonic long-range LFC (laminar flow control) aircraft were performed with the aim of maximizing L/D and alleviating sonic boom during supersonic cruise. It is found that configurations with highly swept LFC wings of very high structural aspect ratio, with the sweep increasing toward the wing root and braced externally by wide chord laminarized struts, appear especially promising. In the supersonic cruise design condition the wing upper surface isobars are swept such that the flow in the direction normal to them is transonic with embedded supersonic zones and practically shock-free over most of the span, with M-perpendicular equal to the two-dimensional design values of advanced SC LFC airfoils, e.g., of the X-787 or X-6 type.
    Keywords: AERODYNAMICS
    Type: ICAS Congress; Sept. 9-14, 1990; Stockholm; Sweden
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  • 8
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    Design of low Reynolds number airfoils. II (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Low Reynolds number airfoils were designed for high lift-to-drag ratios. Design considerations of low Re-airfoils are discussed and design examples are presented. It is shown that the performance of advance low Reynolds airfoils critically depends on proper laminar separation and transition control for the minimum profile drag coefficient with minimum turbulator device drag. This transition control close to the laminar separation is possible by enforcing transition on the upper surface either directly by means of spanwise rows of three-dimensional roughness elements, bleed or suction holes, or indirectly by means of destabilizing the upper surface boundary layer by means of backward facing surface steps, two-dimensional or zig-zag tapes or weak boundary layer blowing. Pneumatic turbulators are found to be advantageous because they can be adjusted to different external flow conditions better than mechanical ones.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 88-3764 , AIAA, ASME, SIAM, and APS, National Fluid Dynamics Congress; Jul 25, 1988 - Jul 28, 1988; Cincinnati, OH; United States
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  • 9
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    Design of low Reynolds number airfoils. I (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The low Reynolds number airfoils designated ASM-LRN-003 and -007 have been designed for high section L/D ratios using Drela's (1985) design-and-analysis code; close to 70-percent laminar flow is maintained on the upper surfaces, and 100-percent on the lower, at coefficients of lift of 1.0-1.3, assuming optimum laminar separation and transition control on the upper surface by means of suitable turbulators. If peak performance is critical, airfoils of this type with an undercut front lower surface and a correspondingly sharper leading edge may be resorted to.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 88-2572 , AIAA Applied Aerodynamics Conference; Jun 06, 1988 - Jun 08, 1988; Williamsburg, VA; United States
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  • 10
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    Design of low Reynolds number airfoils. I (1990)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 27; 204-210
    Format: text
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