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  • 1
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    Efficient simulation of incompressible viscous flow over single and multielement airfoils (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 30; 5; p. 736-743.
    Format: text
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  • 2
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    Upwind differencing scheme for the time-accurate incompressible Navier-Stokes equations (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 28; 253-262
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  • 3
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    Computations of three-dimensional steady and unsteady viscous incompressible flows (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The INS3D family of computational fluid dynamics computer codes is presented. These codes are used to as tools in developing and assessing algorithms for solving the incompressible Navier-Stokes equations for steady-state and unsteady flow problems. This work involves applying the codes to real-world problems involving complex three-dimensional geometries. The algorithms utilized include the method of pseudocompressibility including both central and upwind differencing, several types of artificial dissipation schemes, approximate factorization, and an implicit line-relaxation scheme. These codes have been validated using a wide range of problems including flow over a backward-facing step, driven cavity flow, flow through various types of ducts, and steady and unsteady flow over a circular cylinder. Many diverse flow applications have been solved using these codes including parts of the Space Shuttle Main Engine, problems in naval hydrodynamics, low-speed aerodynamics, and biomedical fluid flows. The presentation details several of these, including the flow through a Space Shuttle Main Engine inducer, vortex shedding behind a circular cylinder, and flow through an artificial heart.
    Keywords: AERODYNAMICS
    Type: NASA Computational Fluid Dynamics Conference. Volume 1: Sessions 1-6; p 223-237
    Format: application/pdf
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  • 4
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    Analysis of a fixed-pitch X-wing rotor employing lower surface blowing (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Lower surface blowing (LSB) is investigated as an alternative to the variable blade pitch requirement for the X-wing Circulation Control (CC) rotor concept. Addition trailing edge blowing slots on the lower surfaces of CC airfoils provide a bidirectional lift capability that effectively doubles the control range. The operational requirements of this rotor system are detailed and compared to the projected performance attributes of LSB airfoils. Analysis shows that, aerodynamically, LSB supplies a fixed pitch rotor system with the equivalent lift efficiency and rotor control of present CC rotor designs that employ variable blade pitch. Aerodynamic demands of bidirectional lift production are predicted to be within the capabilities of current CC airfoil design methodology. Emphasis in this analysis is given to the high speed rotary wing flight regime unique to stoppable rotor aircraft. The impact of a fixed pitch restriction in hover and low speed flight is briefly discussed.
    Keywords: AERODYNAMICS
    Type: NASA. Ames Research Center Proceedings of the Circulation-Control Workshop, 1986; p 363-380
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  • 5
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    Efficient simulation of incompressible viscous flow over multi-element airfoils (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The incompressible, viscous, turbulent flow over single and multi-element airfoils is numerically simulated in an efficient manner by solving the incompressible Navier-Stokes equations. The computer code uses the method of pseudo-compressibility with an upwind-differencing scheme for the convective fluxes and an implicit line-relaxation solution algorithm. The motivation for this work includes interest in studying the high-lift take-off and landing configurations of various aircraft. In particular, accurate computation of lift and drag at various angles of attack, up to stall, is desired. Two different turbulence models are tested in computing the flow over an NACA 4412 airfoil; an accurate prediction of stall is obtained. The approach used for multi-element airfoils involves the use of multiple zones of structured grids fitted to each element. Two different approaches are compared: a patched system of grids, and an overlaid Chimera system of grids. Computational results are presented for two-element, three-element, and four-element airfoil configurations. Excellent agreement with experimental surface pressure coefficients is seen. The code converges in less than 200 iterations, requiring on the order of one minute of CPU time (on a CRAY YMP) per element in the airfoil configuration.
    Keywords: AERODYNAMICS
    Type: California State Univ., The Fifth Symposium on Numerical and Physical Aspects of Aerodynamic Flows; 10 p
    Format: application/pdf
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  • 6
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    Numerical predictions of residence times behind a rearward facing step with transverse injection (1983)
    In:  Other Sources
    Details
    Publication Date: 2017-10-02
    Description: A numerical investigation of the two-dimensional recirculation zone formed between a rear-ward facing step and a transverse hydrogen jet in a supersonic flow is presented. Calculations were made using an elliptic flow computer code with a time-relaxation finite difference integration algorithm. Cases were examined for jet static pressures between 2 and 5 times mainstream with jets located 3 to 7 step heights downstream of the step. Nominal mainstream flow conditions were Mach 2.4 air at 1 atm pressure and 1000K (1800R) static temperature. Results in the form of mean properties in the recirculation zone and residence time are presented. Calculations of the decay of hydrogen mass from the steady state are presented for selected cases. The combustion potential for each case is assessed by comparison of computed conditions in the recirculation zone with the results from a well-stirred reactor theory.
    Keywords: AERODYNAMICS
    Type: APL The 20th JANNAF Combust. Meeting, Vol. 1; p 635-652
    Format: text
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  • 7
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    Efficient simulation of incompressible viscous flow over multi-element airfoils (1993)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: The incompressible, viscous, turbulent flow over single and multi-element airfoils is numerically simulated in an efficient manner by solving the incompressible Navier-Stokes equations. The solution algorithm employs the method of pseudo compressibility and utilizes an upwind differencing scheme for the convective fluxes, and an implicit line-relaxation scheme. The motivation for this work includes interest in studying high-lift take-off and landing configurations of various aircraft. In particular, accurate computation of lift and drag at various angles of attack up to stall is desired. Two different turbulence models are tested in computing the flow over an NACA 4412 airfoil; an accurate prediction of stall is obtained. The approach used for multi-element airfoils involves the use of multiple zones of structured grids fitted to each element. Two different approaches are compared; a patched system of grids, and an overlaid Chimera system of grids. Computational results are presented for two-element, three-element, and four-element airfoil configurations. Excellent agreement with experimental surface pressure coefficients is seen. The code converges in less than 200 iterations, requiring on the order of one minute of CPU time on a CRAY YMP per element in the airfoil configuration.
    Keywords: AERODYNAMICS
    Type: AGARD, High-Lift System Aerodynamics; 9 p
    Format: text
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  • 8
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    Comparisons of Theoretical and Experimental Pressure Distributions on an Arrow-Wing Configuration at Subsonic, Transonic, and Supersonic Speeds (1977)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: A wind tunnel test of an arrow wing body configuration consisting of flat and twisted wings, as well as a variety of leading- and trailing-edge control surface deflection, has been conducted at Mach numbers from 0.40 to 2.50 to provide an experimental data base for comparison with theoretical methods. Theory-to-experiment comparisons of detailed pressure distributions have been made using current state-of-the-art attached- and separated-flow methods. The purpose of these comparisons was to delineate conditions under which these theories are valid for aeroelastic calculations and to explore the use of empirical methods to correct the theoretical methods where theory is deficient. It was determined that current state-of-the-art attached flow and empirical methods were inadequate to predict aeroelastic loads for this configuration.
    Keywords: AERODYNAMICS
    Type: AGARD Prediction of Aerodynamic Loading; 14 p
    Format: text
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  • 9
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    Numerical predictions of residence times behind a rearward facing step with transverse injection (1983)
    In:  Other Sources
    Details
    Publication Date: 2018-12-01
    Description: A numerical investigation of the two-dimensional recirculation zone formed between a rearward facing step and a transverse hydrogen jet in a supersonic flow is presented. Calculations were made using an elliptic flow computer code with a time-relaxation finite difference integration algorithm. Cases were examined for jet static pressures between 2 and 5 times mainstream with jets located 3 to 7 step heights downstream of the step. Nominal mainstream flow conditions were Mach 2.4 air at 1 atm pressure and 1000 K (1800 R) static temperature. Results in the form of mean properties in the recirculation zone and residence time are presented. Calculations of the decay of hydrogen mass from the steady state are presented for selected cases. The combustion potential for each case is assessed by comparison of computed conditions in the recirculation zone with the results from a well-stirred reactor theory.
    Keywords: AERODYNAMICS
    Format: text
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  • 10
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    A numerical study of three-dimensional incompressible flow around multiple posts (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The incompressible laminar flow around single and double rows of an infinite number of posts between two flat plates has been calculated numerically. A C-grid with periodic boundary conditions has been used. The angle of attack, measured from the line normal to the row of posts, was varied between zero and less than 90 deg. The pressure loading was computed for all of the posts in each of these cases. Most of these calculations have been carried out on the Numerical Aerodynamic Simulation Cray 2 at NASA Ames Research Center.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 86-0353
    Format: text
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