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IMPROVEMENTS TO AN EULER AERODYNAMIC METHOD FOR TRANSONIC FLOW-ANALYSIS

JOURNAL OF AIRCRAFT 1989年第1期26卷 13-20页

作者： RAJ, P BRENNAN, JE Lockheed Aeronautical Systems Company Burbank California

Modifications to a three-dimensional Euler aerodynamic method (TEAM) and their effect on the accuracy of transonic flow simulations are described. TEAM’S solution algorithm is based on a finite-volume spatial discretization and multistage time-stepping algorithm to solve the Euler equations. Treatment of numerical dissipation and surface boundary condition are specifically addressed. The modified code includes the standard adaptive dissipation scheme using blended second and fourth differences and a flux-limited dissipation scheme. Improved treatment of the surface boundary condition minimizes spurious entropy production. TEAM computations are correlated with experimental data for two wings, ONERA M-6 and Wing C, and an arrow wing-body configuration. For Wing C, the TEAM predictions are also compared with those of the full-potential TWING code on identical grids. © American Institute of Aeronautics and Astronautics, Inc., 1987.

关键词： Potential Flow Wing Body Configuration Euler Equations solution algorithm Entropy Lift Coefficient Freestream Conditions Aspect Ratio NACA 0012 Static Pressure

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FAR-FIELD COMPUTATIONAL BOUNDARY-CONDITIONS FOR 2-DIMENSIONAL EXTERNAL FLOW PROBLEMS

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AIAA JOURNAL 1992年第11期30卷 2585-2594页

作者： VERHOFF, A STOOKESBERRY, D AGRAWAL, S McDonnell Aircraft Company St. Louis Missouri 63166

Far-field computational boundary conditions for external flow problems have been developed from analytic solutions of the linearized steady-state Euler equations. These boundary conditions have improved accuracy compared with commonly used characteristic boundary conditions. The Euler equations are linearized about a constant pressure, rectilinear flow condition that truly represents conditions at infinity. Because the Euler equations are used to develop the boundary conditions, the now crossing the boundary can be rotational. The boundary conditions can be used with any numerical Euler solution method and allow computational boundaries to be located very close to the nonlinear region of interest. This leads to a significant reduction in the number of grid points required for numerical solution. Numerical results are presented that show that the boundary conditions and far-field analytic solutions provide a smooth transition across a computational boundary to the true far-field conditions at infinity. They also demonstrate the synergism that can be realized from coupling analytic and computational methods. Computational efficiency gains are shown to be substantial.

关键词： External Flows Euler Equations Computational Methods Freestream Mach Number Lift Coefficient solution algorithm Stagnation Temperature Integral Transform Unstructured Grid NACA 0012

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IMPROVED CALCULATION OF TRANSONIC POTENTIAL FLOW PAST SWEPT WINGS

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JOURNAL OF AIRCRAFT 1992年第5期29卷 961-964页

作者： WANG, LX CAUGHEY, DA Cornell University Ithaca New York 14853

In spite of recent advances in numerical methods to solve the Euler and Navier-Stokes equations for transonic flow problems, the transonic potential equation is still widely used in design work. Among the algorithms for solving three-dimensional transonic potential flows, the computer program Flo-22 developed by A. Jameson and D.A. Caughley has proved to be economical and robust for many practical applications. The purpose of this paper is to describe some recent improvements in Flo-22, that include a chordwise scaling to render the trailing edge a grid line, and a modification to the symmetry plane boundary condition to better enforce the noflux condition there. Results are presented for the transonic flow past a supercritical wing, using the original and modified versions of Flo-ww, as well as the fully-conservative Euler code developed by Y. Yadlin and D.A. Caughey.

关键词： Potential Flow Swept Wing Freestream Mach Number Lift Coefficient Wing Root solution algorithm Supercritical Wings Tapered Wings Finite Difference Method Navier Stokes Equations

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2ND-ORDER, FAR-FIELD COMPUTATIONAL BOUNDARY-CONDITIONS FOR INVISCID DUCT FLOW PROBLEMS

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AIAA JOURNAL 1992年第5期30卷 1268-1276页

作者： VERHOFF, A STOOKESBERRY, D McDonnell Aircraft Company St. Louis Missouri 63166

Highly accurate far-field computational boundary conditions for two-dimensional, inviscid, isentropic duct flow problems are developed from analytic solutions of the linearized, second-order Euler equations. The Euler equations are linearized about a constant pressure, rectilinear flow condition that truly represents conditions at infinity. The boundary procedure can be used with any numerical Euler solution method and allows computational boundaries to be located extremely close to the nonlinear region of interest. Numerical results are presented that show that the boundary conditions and far-field analytic solutions provide a smooth transition across a computational boundary to the true far-field conditions at infinity. They also demonstrate the synergism that can be realized from coupling analytic and computational methods. The cost of upgrading first-order boundary conditions to second order is slight.

关键词： Euler Equations Computational Methods Freestream Conditions External Flows Nozzle Geometry Mass Flow Stagnation Temperature solution algorithm Specific Heat

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STRAKE-GENERATED VORTEX INTERACTIONS FOR A FIGHTER-LIKE CONFIGURATION

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JOURNAL OF AIRCRAFT 1989年第4期26卷 289-294页

作者： REZNICK, SG FLORES, J U.S. Space Command Headquarters Peterson Air Force Base Colorado NASA Ames Research Center Moffett Field California

A combination of the Euler and thin-layer Navier-Stokes equations were solved for the flowfield around a wingstrake- fuselage configuration similar to the General Dynamics F-16A aircraft. Steady-state solutions were obtained at angles-of-attack ranging from 6 to 10 deg at M_∞ = 0.3, 0.6, and 0.9, and Reynolds numbers matching those of wind-tunnel and water-tunnel experiments. The flowfield was divided into multiple blocks using a zoning program and the transonic Navier-Stokes wing-fuselage (TNSWF) solution program, based on an implicit solution algorithm, which updates each subregion of the flowfield sequentially. The total grid contained approximately 300, 000 grid points, and clustering was affected normal to all aircraft surfaces. The computed solutions agreed well quantitatively with wind-tunnel pressure distribution data, and they agreed well qualitatively with flow visualization from wind- and water-tunnel tests. © 1989 American Institute of Aeronautics and Astronautics, Inc.

关键词： Aircraft Configurations Vortices Reynolds Averaged Navier Stokes Angle of Attack Reynolds Numbers Wind Tunnels Navier Stokes Equations solution algorithm Irrotational Flow Wing Root

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Optimal Deployment of Flood Emergency Response Materials under Stochastic Demands

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JOURNAL OF MARINE SCIENCE AND TECHNOLOGY 2022年第2期30卷 86-101页

作者： Yan, Shangyao Lin, Jenn-Rong Ku, Chia-Fu Natl Cent Univ Dept Civil Engn Taoyuan 32001 Taiwan Natl Taiwan Ocean Univ Dept Transportat Sci Keelung 20224 Taiwan

This study aims to develop a planning model for the deployment of flood emergency response materials under stochastic demands. For ease of modeling, a deterministic demand model is first proposed, from which the stochastic model is further extended. These models are used to determine the allocation of materials the transport truck routes and distribution of the stockpiled materials to emergency sites. The models are formulated as multiple integer network flow problems with special side constraints which are characterized as NP-hard in terms of optimization. To solve the complicated stochastic model efficiently, we also develop a solution algorithm based on a problem decomposition technique coupled with a variable fixing technique. Finally, to preliminarily evaluate the proposed models and solution algorithm, we perform numerical tests using data related to a Taiwan flood emergency response system. The test results are good, indicating the potential usefulness of the models and solution algorithm in practice.

关键词： Flood emergency response Material deployment Time-space network Stochastic demand solution algorithm

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CALCULATION OF AXISYMMETRICAL, TURBULENT, CONFINED DIFFUSION FLAMES

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AIAA JOURNAL 1986年第3期24卷 462-469页

作者： VANKA, SP Argonne National Laboratory Argonne Illinois

A solution algorithm based on a fully coupled solution of the time-averaged Navier-Stokes equations is developed for the calculation of turbulent reacting flows. The governing elliptic partial differential equations are discretized by finite differences and the nonlinear algebraic equations are solved by a block-implicit algorithm employing Newton’s method and sparse matrix techniques. Calculations have been made of a confined turbulent diffusion flame. Turbulence is represented by the k - ∈ model and chemical reaction is assumed to occur in one step at an infinite rate, controlled by the mixing of fuel and oxidant streams. It is demonstrated that the strategy of a coupled solution is rapidly convergent even in the presence of significant density variations. Calculations with finite difference grids as large as 80 × 100 have been made successfully in modest computer time and with modest storage. The calculations are compared with experimental data. © 1986 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.

关键词： Fuel Air Ratio Continuity Equation Chemically Reacting Flow Aspect Ratio Kinetic Energy solution algorithm Numerical Stability Shear Layers Gaseous Fuel Turbulence Models

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EFFICIENT SIMULATION OF INCOMPRESSIBLE VISCOUS-FLOW OVER SINGLE AND MULTIELEMENT AIRFOILS

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JOURNAL OF AIRCRAFT 1993年第5期30卷 736-743页

作者： ROGERS, SE WILTBERGER, NL KWAK, D NASA Ames Research Center Moffett Field California 94035

The incompressible, viscous, turbulent flow over single and multielement airfoils is numerically simulated in an efficient manner by solving the incompressible Navier-Stokes equations. The solution algorithm uses the method of pseudocompressibility with 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 takeoff 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 a NACA 4412 airfoil;an accurate prediction of stall is obtained. The approach used for multielement airfoils involves the use of multiple zones of structured grids fitted to each element. Two different approaches are compared: 1) a patched system of grids, and 2) an overlaid Chimera system of grids. Computational results are presented for two-element, three-element, and four-element airfoil configurations. Generally, good agreement with experimental surface pressure coefficients is seen. The code converges in less than 200 iterations, requiring on the order of 1 min of CPU time on a CRAY YMP per element in the airfoil configuration.

关键词： Incompressible Viscous Flow Lift Coefficient Supercritical Airfoils Reynolds Averaged Navier Stokes Baldwin Lomax Turbulence Model Navier Stokes Calculations Takeoff and Landing Computing solution algorithm Earth

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3-DIMENSIONAL INVISCID FLOW IN MIXERS .1. MIXER ANALYSIS USING A CARTESIAN GRID

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JOURNAL OF PROPULSION AND POWER 1986年第3期2卷 275-281页

作者： BARBER, TJ MULLER, GL RAMSAY, SM MURMAN, EM PRATT & WHITNEY AIRCRAFT E HARTFORDCT 06108 MIT AERONAUT & ASTRONAUTCAMBRIDGEMA 02139

A three-dimensional potential flow analysis has been formulated and applied to the inviscid flow over a turbofan forced mixer. In Part I, a method using a novel small disturbance formulation is presented which analytically uncouples the circumferential flow from the radial and axial flow problem, thereby reducing the analysis to the solution of a series of axisymmetric problems. These equations are discretized using a flux volume formulation along a Cartesian grid. The method extends earlier applications of the Cartesian method to complex cambered multicomponent geometries. Calculations are presented for a symmetric mixer in a planar duct. Good agreement is obtained with a small disturbance singularity superposition analysis. In Part II, the method is extended to treat flows with different energy levels and applied to experimentally tested turbofan forced mixer geometries. © 1986 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.

关键词： One Dimensional Flow Pressure Coefficient Vortex Sheet Compressibility Static Pressure Mach Numbers Mass Flux Turbofan solution algorithm Gas Turbine Engines

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UNSTRUCTURED ADAPTIVE MESH COMPUTATIONS OF ROTORCRAFT HIGH-SPEED IMPULSIVE NOISE

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JOURNAL OF AIRCRAFT 1995年第4期32卷 754-760页

作者： STRAWN, RC BISWAS, R GARCEAU, M NASA Ames Research Center Moffett Field California 94035 Stanford University Stanford California 94305

A new method is developed for modeling helicopter high-speed impulsive (HSI) noise. The aerodynamics and acoustics near the rotor blade tip are computed by solving the Euler equations on an unstructured grid, A stationary Kirchhoff surface integral is then used to propagate these acoustic signals to the far field, The near-field Euler solver uses a solution-adaptive grid scheme to improve the resolution of the acoustic signal, Grid points are locally added and/or deleted from the mesh at each adaptive step, An important part of this procedure is the choice of an appropriate error indicator, The error indicator is computed from the flowfield solution and determines the regions for mesh coarsening and refinement, Computed results for HSI noise compare favorably with experimental data for three different hovering rotor cases.

关键词： Rotary Wing Aerodynamics Unstructured Grid Rotor Blades Acoustics Helicopter Rotor Euler Equations Supersonic Flow solution algorithm Tetrahedral Element

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