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  • 1985-1989  (27)
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  • 1
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    Applications of classical and zero-total-pressure-loss sets of Euler equations to delta wings (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Classical and zero-total pressure-loss sets of Euler equations were applied to sharp- and round-edge delta wings. The origin of the total pressure was explained in the classical set. For sharp-edged delta wings, all sets of Euler equations produce the same separated flow solutions. For round-edged delta wings and for coarse grids, the solution depends on the level of dissipation, the accuracy of the surface boundary condition, and the type of Euler equations set. For round-edged delta wings and for fine grids, attached flow solutions are obtained. Also presented were three dimensional flow solutions and asymmetric flow solutions including unsteady flow for sharp-edged delta wings. Euler equations should be restricted to sharp-edged wings for real flow solutions. For roung-edged wings, Navier-Stokes equations must be used.
    Keywords: AERODYNAMICS
    Type: Unsteady Hybrid Vortex Technique for Transonic Vortex Flows and Flutter Applications; 29 p
    Format: application/pdf
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  • 2
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    Transonic airfoil computation using the integral equation with and without embedded Euler domains (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Two transonic computational schemes which are based on the Integral Equation Formulation of the full potential equation were presented. The first scheme is a Shock Capturing-Shock Fitting (SCSF) scheme which uses the full potential equation throughout with the exception of the shock wave where the Rankine-Hugoniot relations are used to cross and fit the shock. The second scheme is an Integral Equation with Embedded Euler (IEEE) scheme which uses the full potential equation with an embedded region where the Euler equations are used. The two schemes are applied to several transonic airfoil flows and the results were compared with numerous computational results and experimental domains with fine grids. The SCSF-scheme is restricted to flows with weak shock, while the IEEE-scheme can handle strong shocks. Currently, the IEEE scheme is applied to other transonic flows with strong shocks as well as to unsteady pitching oscillations.
    Keywords: AERODYNAMICS
    Type: Unsteady Hybrid Vortex Technique for Transonic Vortex Flows and Flutter Applications; 15 p
    Format: application/pdf
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  • 3
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    Navier-Stokes computations of separated vortical flows past prolate spheroid at incidence (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The problem of steady incompressible viscous flow past prolate spheroids at incidence is formulated using the unsteady incompressible and compressible thin-layer Navier-Stokes equations. The two sets of Navier-Stokes equations are solved using a pseudotime stepping of the implicit flux-difference splitting scheme on a curvilinear grid, which is generated by a transfinite grid generator. The Baldwin and Lomax (1978) algebraic eddy-viscosity model is used to model the turbulent flow. The computational applications cover a 6:1 prolate spheroid at different angles of attack and Reynolds numbers. The results are compared with experimental data.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 89-0553
    Format: text
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  • 4
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    Unsteady Navier-Stokes computations past oscillating delta wing at high incidence (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The unsteady, thin-layer, compressible Navier-Stokes equations, written in the moving frame of reference for the flow relative motion, is solved for the steady and unsteady supersonic flow around a round-edged delta wing. For supersonic flow, local conical flow solution has been obtained from the three-dimensional equations. Pseudotime stepping is used for the steady flow, while time-accurate stepping is used for the unsteady flow. The computational scheme is an implicit approximately-factored finite volume scheme which uses explicit and implicit dissipation terms. The scheme is verified for the steady flow solution. The scheme is then applied to a delta wing undergoing rolling oscillation at a reduced frequency of 1.137 with 15- deg maximum amplitude about a mean angle of attack of 10 deg for a Mach number of 2 and a Reynolds number of 500,000.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 89-0081
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  • 5
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    Solution of steady and unsteady transonic-vortex flows using Euler and full-potential equations (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Two methods are presented for inviscid transonic flows: unsteady Euler equations in a rotating frame of reference for transonic-vortex flows and integral solution of full-potential equation with and without embedded Euler domains for transonic airfoil flows. The computational results covered: steady and unsteady conical vortex flows; 3-D steady transonic vortex flow; and transonic airfoil flows. The results are in good agreement with other computational results and experimental data. The rotating frame of reference solution is potentially efficient as compared with the space fixed reference formulation with dynamic gridding. The integral equation solution with embedded Euler domain is computationally efficient and as accurate as the Euler equations.
    Keywords: AERODYNAMICS
    Type: NASA, Langley Research Center, Transonic Unsteady Aerodynamics and Aeroelasticity 1987, Part 2; p 261-311
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  • 6
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    Euler/Navier-Stokes zonal scheme with applications to separated and isolated-vortex flows (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An Euler/Navier-Stokes zonal scheme with boundary-layer compatibility conditions is developed to economically compute separated and vortex flows. The scheme is based on dividing the flow region into zones, where different levels of mathematical approximations of the governing equations are used in each zone. The scheme is applied to two specific problems: the two dimensional flow over a blunt leading-edge plate and the quasi-axisymmetric flow of an isolated vortex core. In the first problem, the computational domain is divided into inner and outer zones where the Navier-Stokes and Euler equations are used, respectively. On the downstream boundary of the computational domain, boundary-layer compatibility conditions are used. In the second problem, boundary-layer-like equations for slender, compressible, vortex flows are developed. A compatibility condition has been used to ensure consistency of the boundary and initial conditions. The outer boundary conditions of the flow are derived from Euler equations for a stream surface.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 88-0507
    Format: text
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  • 7
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    Unsteady vortex-dominated flows around maneuvering wings over a wide range of Mach numbers (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The problem of unsteady flow around maneuvering wings is solved using the unsteady Euler equations. The unsteady conservative Euler equations are derived for the flow relative motion with respect to a moving (translating and rotating) frame of reference. The resulting equations can handle the most general case for unsteady three-dimensional flow around maneuvering wings or wing-body configurations undergoing six degrees of freedom motion; three translations and three rotations. The equations are solved using two computational schemes; an explicit multistage finite-volume scheme and an implicit approximately factored finite-volume scheme. The computational applications cover two cases. The first case is for a locally conical supersonic flow of rolling oscillation of a sharp-edged delta wing at zero angle of attack. The second case is for a pitching oscillation around a mean angle of attack of a NACA 0012 airfoil in transonic flow.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 88-0317
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  • 8
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    Vortical flow aerodynamics - Physical aspects and numerical simulation (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Progress in the numerical simulation of vortical flow due to three-dimensional flow separation about flight vehicles at high angles of attack and quasi-steady flight conditions is surveyed. Primary emphasis is placed on Euler and Reynolds-averaged Navier-Stokes methods where the vortices are 'captured' as a solution to the governing equations. A discussion of the relevant flow physics provides a perspective from which to assess numerical solutions. Current numerical prediction capabilities and their evolutionary development are surveyed. Future trends and challenges are identified and discussed.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 87-0205
    Format: text
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  • 9
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    Finite-volume Euler and Navier-Stokes solvers for three-dimensional and conical vortex flows over delta wings (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A unified central-difference finite-volume Euler and Navier-Stokes solver with four-stage Runge-Kutta time stepping is presented. The computer code developed for this purpose is capable of solving the standard set and nonstandard sets (zero-total-pressure loss) of Euler equations and the thin-layer and full Navier-Stokes equations. Applications are presented for conical supersonic flows with weak shocks using the standard and nonstandard sets of Euler equations, and the thin-layer and full Navier-Stokes equations for sharp and round-edged delta wings. Applications are also presented for three-dimensional transonic and subsonic flows using the standard set of Euler equations for sharp-edged delta wings. The computational results of the different sets of equations are compared with each other and with the experimental results and conclusions on the validity of these sets to these applications, are presented.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 87-0041
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  • 10
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    Integral equation solution of the full potential equation for transonic flows (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An integral equation method for solving the full potential equation has been developed for arbitrary configurations in two- or three-dimensional transonic flows. This method is capable of capturing shocks using Murman-Cole type of finite difference scheme and is capable of predicting accurate and force-free wake shape as well. A rectangular grid combined with a technique of local grid refinement greatly improved the computational efficiency.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 89-0563
    Format: text
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