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  • 1
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    Heat transfer in the vicinity of two- dimensional protuberances. (1964)
    In:  Other Sources
    Details
    Publication Date: 2019-05-24
    Description: Heat transfer coefficients in vicinity of two- dimensional protuberances in supersonic flow
    Keywords: AERODYNAMICS
    Format: text
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  • 2
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    Flight test and numerical simulation of transonic flow around YAV-8B Harrier II wing (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A computational fluid dynamics (CFD) method is used to study the aerodynamics of the YAV-8B Harrier II wing in the transonic region. A numerical procedure is developed to compute the flow field around the complicated wing-pylon-fairing geometry. The surface definition of the wing and pylons were obtained from direct measurement using theodolite triangulation. A thin-layer Navier-Stokes code with the Chimera technique is used to compute flow solutions. The computed pressure distributions at several span stations are compared with flight test data and show good agreement. Computed results are correlated with flight test data that show the flow is severely separated in the vicinity of the wing-pylon junction. Analysis shows that shock waves are induced by pylon swaybrace fairings, that the flow separation is much stronger at the outboard pylon and that the separation is caused mainly by the crossflow passing the geometry of wing-pylon junction.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 91-1628
    Format: text
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  • 3
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    Implicit and explicit computations of flows past cavities with and without yaw (1990)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Implicit and explicit computations are presented to study the supersonic, turbulent flows past three-dimensional, rectangular cavities at 0 and 45 deg yaw angle. The Reynolds-averaged, unsteady, compressible, complete Navier-Stokes equations are solved time-accurately, including the Reynolds stresses. The number of major vortices inside and the separation characteristics on the cavity floor are different for cavities with length-to-depth ratios of 3.0 and 6.7. Due to the oscillations of the shear layer, which randomly exposes the cavity flow to the external flow, vortices are shed into the mainstream. When the upstream flow approaches a cavity at yaw, the width-to-depth ratio also becomes an important parameter. The dominant rotational planes of the major vortices incline at an angle to the vertical plane due to yaw. The execution of the implicit scheme is about three times faster, but it requires about four times more computer memory.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 90-0049
    Format: text
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  • 4
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    Full potential methods for analysis/design of complex aerospace configurations (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The steady form of the full potential equation, in conservative form, is employed to analyze and design a wide variety of complex aerodynamic shapes. The nonlinear method is based on the theory of characteristic signal propagation coupled with novel flux biasing concepts and body-fitted mapping procedures. The resulting codes are vectorized for the CRAY XMP and the VPS-32 supercomputers. Use of the full potential nonlinear theory is demonstrated for a single-point supersonic wing design and a multipoint design for transonic maneuver/supersonic cruise/maneuver conditions. Achievement of high aerodynamic efficiency through numerical design is verified by wind tunnel tests. Other studies reported include analyses of a canard/wing/nacelle fighter geometry.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3982 , NAS 1.26:3982
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  • 5
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    Full potential aerodynamic prediction capability for complex configurations (1983)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center, Theoretical Aerodynamics Contractors' Workshop, Volume 2; p 495-53
    Format: text
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  • 6
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    Kinematic domain decomposition to simulate flows past moving objects (1991)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A new method is developed to solve the unsteady Navier-Stokes equations on a composite grid which consists of subdomain grids moving with respect to each other. These subdomains are structured grids with different topologies. However, their interfaces are unstructured in the sense that they may or may not arbitrarily overlap with each other. This method captures the boundary-motion-induced flow component. The method is demonstrated for a transonic flow past an airfoil which experiences a combined motion of pitching and plunging.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 91-0725
    Format: text
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  • 7
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    Development of the wake behind a circular cylinder impulsively started into rotatory and rectilinear motion: Intermediate rotation rates (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The temporal development of two-dimensional viscous incompressible flow generated by a circular cylinder started impulsively into steady rotatory and rectilinear motion is studied by integration of a velocity/vorticity formulation of the governing equations, using an explicit finite-difference/pseudo-spectral technique and an implementation of the Biot-Savart law. Results are presented for a Reynolds number of 200 (based on the cylinder diameter 2a and the magnitude U of the rectilinear velocity) for several values of the angular/rectilinear speed ratio alpha = (omega x a)/U (where omega is the angular speed) up to 3.25. Several aspects of the kinematics and dynamics of the flow not considered earlier are discussed. For higher values of alpha, the results indicate that for Re = 200, vortex shedding does indeed occur for alpha = 3.25. The shedding process is; however, very different from that which gives rise to the usual Karman vortex street for alpha = 0. In particular, consecutive vortices shed by the body can be shed from the same side and be of the same sense, in contrast to the nonrotating case, in which mirror-image vortices of opposite sense are shed alternately on opposite sides of the body. The implications of the results are discussed in relation to the possibility of suppressing vortex shedding by open or closed-loop control of the rotation rate.
    Keywords: AERODYNAMICS
    Type: NASA-CR-187512 , ICASE-91-10 , NAS 1.26:187512 , AD-A233295
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  • 8
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    Development and validation of CNS (compressible Navier-Stokes) for hypersonic external flows (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: CNS, a new computational fluid dynamics procedure, has been developed to aid in hypersonic vehicle design. The code can be used to model the entire external flow around hypersonic vehicle shapes, from the captured shock at the nose to the beginning of the wake. Unlike space-marching codes, the technique allows axially separated flow regions to be modeled. Validation trials using sphere-cone data reveal good solution accuracy for the surface pressure and flowfield temperature.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 89-1839
    Format: text
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  • 9
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    Computation of viscous transonic flow over porous airfoils (1987)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The viscous effects on transonic flow past an airfoil which contains a shallow cavity beneath a porous surface are studied numerically. The porous region occupies a small portion of the total airfoil surface, and is located near the shock. Both an interactive boundary layer (IBL) algorithm and a thin-layer Navier-Stokes (TLNS) algorithm have been modified for use in studying the outer flow, whereas a stream-function formulation has been used to model the inner flow in the small cavity. The coupling procedure at the porous surface is based on Darcy's law and on the assumption of a constant total presusre in the cavity. In addition, a modified Baldwin-Lomax turbulence model is used to consider the transpired turbulent boundary layer in the TLNS approach, and the Cebeci-Smith turbulence model is used in the IBL approach. According to the present analysis, a porous surface can reduce the wave drag appreciably, but it can also increase viscous losses. As has been observed experimentally, the numerical results indicate that the total drag is reduced at higher Mach numbers and increased at lower Mach numbers when the angles of attack are small. Furthermore, the streamline patterns of passive-shock and boundary-layer interaction are revealed in this study.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 87-0359
    Format: text
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  • 10
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    Supersonic flow computations over aerospace configurations using an Euler marching solver (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: For fully supersonic flows, an efficient strategy for obtaining numerical solutions is to employ space marching techniques. A full potential marching technique, known as the SIMP code and capable of handling such embedded subsonic regions, has achieved some success analyzing low supersonic Mach number flows. The extension of the full potential approach to the Euler equation which model the exact nonlinear inviscid gas dynamic flow processes is presented. Within the assumption of an inviscid flow, such an Euler marching solver can be applied to a wide class of shocked flows including the hypersonic range. The intent is to maintain some of the basic features of the full potential SIMP code within the Euler solver in dealing with geometry input, gridding techniques, and input/output routines including post processing of results. An Euler marching code known as EMTAC was developed. Results obtained for a variety of configurations involving canard, wing, horizontal tail, flow-through inlet, and fuselage using both the EMTAC and SIMP codes are reported. For shocked cases satisfying the isentropic assumption, the EMTAC and SIMP codes produced practically the same results. In terms of execution time, the EMTAC code is slower.
    Keywords: AERODYNAMICS
    Type: NASA-CR-4085 , NAS 1.26:4085
    Format: application/pdf
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