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  • 1
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    Incompressible Navier-Stokes computations for a round-edged double-delta wing (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 25; 675
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  • 2
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    Numerical study of vortical flow over a sideslipping delta wing (1990)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The three-dimensional vortical viscous flow past a sideslipping delta wing at a high angle of attack is numerically investigated. A computational method for calculating low-speed viscous flowfields is developed. The time-iterative method uses an implicit upwind-relaxation finite-difference algorithm with a nonsingular eigensystem to solve the preconditioned, three-dimensional, incompressible Navier-Stokes equations in curvilinear coordinates. An algebraic turbulence model is implemented to account for the eddy viscosity. The technique of local time stepping is incorporated to accelerate the rate of convergence to a steady-state solution. Computed results are compared with experimental data.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 90-3001
    Format: text
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  • 3
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    Theory of wing rock (1984)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: A theory is developed for predicting wing rock characteristics. From available data, it can be concluded that wing rock is triggered by flow asymmetries, developed by negative or weakly positive roll damping, and sustained by nonlinear aerodynamic roll damping. A new nonlinear aerodynamic model that includes all essential aerodynamic nonlinearities is developed. The Beecham-Titchener method is applied to obtain approximate analytic solutions for the amplitude and frequency of the limit cycle based on the three degree-of-freedom equations of motion. An iterative scheme is developed to calculate the average aerodynamic derivatives and dynamic characteristics at limit cycle conditions. Good agreement between theoretical and experimental results is obtained.
    Keywords: AERODYNAMICS
    Type: NASA-CR-176640 , NAS 1.26:176640 , CRINC-FRL-516-1
    Format: application/pdf
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  • 4
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    An implicit flux-difference splitting scheme for three-dimensional, incompressible Navier-Stokes solutions to leading edge vortex flows (1986)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A new, implicit finite-difference scheme designed to solve the conservative, flux-difference split Navier-Stokes equations is used to compute incompressible vortex flows around delta wings. The completely vectorizable hybrid algorithm is constructed in delta form for steady state solutions independent of the time-step sizes. The scheme combines approximate factorization in crossflow planes with a symmetric planar Gauss-Seidel relaxation in the remaining spatial direction. The governing equations are solved in curvilinear, body-fitted coordinates for treating complex geometries. The computed flow field results are compared with other theoretical and experimental data.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 86-1839
    Format: text
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  • 5
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    Studies of vortex flow aerodynamics using CFD flow visualizations (1989)
    In:  Other Sources
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    Publication Date: 2018-12-01
    Description: Navier-Stokes computations of three-dimensional vortical flows over a round-edged double-delta wing and a tangent-ogive forebody are performed using an implicit upwind finite-difference scheme. Computed particle traces are compared with experimental oil-flow streaks.
    Keywords: AERODYNAMICS
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  • 6
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    Prediction of vortical flows on wings using incompressible Navier-Stokes equations (1990)
    In:  Other Sources
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    Publication Date: 2018-12-01
    Description: Numerical solutions to the incompressible Navier-Stokes equations are in greater demand than ever before as the field of computational fluid dynamics (CFD) increases its impact as an engineering tool. An implicit upwind-relation finite-difference scheme is developed for solving unsteady incompressible Navier-Stokes equations incorporating an artificial time derivative of the pressure to the continuity equation. The essential features observed in experiments for complicated vortical flows past three round-edged low-aspect-ratio wings at high angles of attack are reproduced both qualitatively and quantitatively.
    Keywords: AERODYNAMICS
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  • 7
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    Upwind Navier-Stokes solutions for leading-edge vortex flows (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An incompressible Navier-Stokes solver using an upwind finite-difference algorithm is employed to investigate low-speed, three-dimensional, laminar, leading-edge vortex flows over three round-edged low-aspect-ratio wings. The effects of grid density, Reynolds number, and wing planform on the flowfield structures and integral values are studied. Computed results show good qualitative and quantitative agreement with the available experimental data.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 89-0265
    Format: text
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  • 8
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    Time-marching methods for three-dimensional steady and unsteady viscous imcompressible flows (1991)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An implicit algorithm for the solution of three-dimensional, steady and unsteady, viscous, incompressible flows is presented. The algorithm is based on an upwind-relaxation finite-difference method. Steady-state solutions are carried out using a time-marching solution technique in combination with a local time-stepping strategy. To obtain time-accurate solutions, a subiterative procedure is employed at each physical time step using a global time step to ensure the divergence-free condition. Steady-state flows in several straight ducts and in a square duct with a 90-degree bend are computed and compared with analytical and experimental results. The classical problem of starting flow in a circular pipe is chosen to verify the time accuracy of the present scheme. Finally, the three-dimensional bubble-type vortex breakdown of a slender cylindrical vortex in an unbounded flow is investigated.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 91-0024
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  • 9
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    Calculations of separated vortex flows at low speed for low-aspect-ratio wings (1992)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: An implicit finite-difference scheme has been developed for solving three-dimensional incompressible Navier-Stokes equations. Computations for complicated vortical flows past several sharp- and round-edged delta and double-delta wings at high angles of attack and sideslip are discussed. Computed results demonstrate the effectiveness of the present method and show good agreement with experimental data.
    Keywords: AERODYNAMICS
    Type: IUTAM Symposium on Fluid Dynamics of High Angle of Attack; Sept. 13-17, 1992; Tokyo; Japan|; 11 p.
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  • 10
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    Numerical study of the vortex burst phenomenon for delta wings (1988)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A flux-difference splitting scheme is employed to compute low-speed flows over a delta wing for angles of attack from 0 to 40 deg as steady-state solutions to the three-dimensional, Reynolds-averaged Navier-Stokes equations in their thin-layer approximation. The finite-difference scheme is made spatially second-order accurate by applying a total variation diminishing-like discretization to the inviscid fluxes and central differencing to the viscous shear fluxes. Using first-order accurate Euler backward-time differencing, an efficient implicit algorithm is constructed, which combines approximate factorization in cross planes with a symmetric planar Gauss-Seidel relaxation in the remaining third spatial direction. The geometry of the thin (maximum thickness is 0.021), slender (aspect ratio is unity), sharp-edged delta wing is taken from Hummel's (1967, 1978) wind tunnel model. Over the entire angle-of-attack range, the computed values of lift and pitching moment are in good agreement with the experimental data. Also details of the flow-fieldlike spanwise surface pressure distributions compare well with the experiment. Computed flow-field results with a bubble-type vortex burst are analyzed in detail.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 88-0505
    Format: text
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