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STRAKE-GENERATED VORTEX INTERACTIONS FOR A FIGHTER-LIKE CONFIGURATION

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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MARKOV RELIABILITY MODELS FOR DIGITAL FLIGHT CONTROL-SYSTEMS

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1989年第2期12卷 209-219页

作者： MCGOUGH, J REIBMAN, A TRIVEDI, K DUKE UNIV DEPT COMP SCIDURHAMNC 27706

The reliability of digital flight control systems can often be accurately predicted! using Markov chain models. We begin our discussion of flight control system reliability models with definitions of key terms. We then construct a single-fault one-processor model based on the results of fault-injection experiments. To illustrate more complex system models, we consider several models of a triple modular redundant system. Once we have constructed some representative Markov reliability models, we discuss numerical techniques for their solution. The cost of numerical solution depends on a model's size and stiffness. Acyclic Markov models, a useful special case, are particularly amenable to efficient numerical solution. Even in the general case, instantaneous coverage approximation allows the reduction of some cyclic models to more readily solvable acyclic models. After considering the solution of single-phase models, we extend our discussion to phased-mission models. We classify phased-mission reliability models based on the state restoration behavior that occurs between mission phases: As an economical approach for the solution of such models, we introduce the mean failure rate solution method. We use a numerical example to show the influence of fault-model parameters and interphase behavior on system unreliability. © 1989 American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Digital Flight Control System Fault Injection Cumulative Distribution Function Numerical Integration Comparators Electromagnetic Interference Flight Control Computer Gaussian Elimination solution algorithm Operating Systems

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SOURCE TERM DECOMPOSITION TO IMPROVE CONVERGENCE OF SWIRLING FLOW CALCULATIONS

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AIAA JOURNAL 1988年第3期26卷 372-374页

作者： JANG, DS ACHARYA, S Louisiana State University Baton Rouge Louisiana

A source term decomposition method is proposed, and it is shown to be computationally advantageous in highly swirling flows. The proposed method uses a corrector form of the tangential momentum equation to decompose t... 详细信息

关键词： Incompressible Flow Shear Layers Radial Velocity Mach Numbers Navier Stokes Equations Diffusion Coefficient Aerospace Engineering Gas Turbine Combustor solution algorithm Vortex Flow

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REDUCED-ORDER COMPENSATION - LINEAR-QUADRATIC REDUCTION VERSUS OPTIMAL PROJECTION

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1988年第4期11卷 328-335页

作者： GREELEY, SW HYLAND, DC Harris Corporation Melbourne Florida

Six methods for design of reduced-order compensation are compared using an example problem. The methods considered comprise five linear-quadratic reduction techniques, reviewed in a recent paper by Liu and Anderson, and the Optimal Projection theory as implemented via a simple homotopy solution algorithm. Design results obtained by the different methods for 42 different design cases are compared with respect to closed-loop stability and transient response characteristics. Of the linear-quadratic reduction procedures, two are found to offer distinctly superior performance. However, only the Optimal Projection method provided stable designs in all cases. Further details are given on the performance of the numerical algorithm for solving the optimal projection equations and the corresponding design results. © 1988 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.

关键词： Closed Loop System solution algorithm Optimal Projection Equations Numerical algorithms Riccati Equations Topological Degree Theory Iterative solution Computing

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PASSIVE VENTING SYSTEM FOR MODIFYING CAVITY FLOWFIELDS AT SUPERSONIC SPEEDS

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AIAA JOURNAL 1988年第3期26卷 374-376页

作者： WILCOX, FJ NASA Langley Research Center Hampton Virginia

The drag of airfoils in transonic flow may be reduced through the use of a passive venting system that uses a porous plate for part of the airfoil upper surface with a vent chamber beneath the porous plate. This arrangement allows air from a high-pressure region on the airfoil surface to be vented to a low-pressure region, thereby modifying the airfoil flow field and resulting indrag reduction. Using this approach, an existing cavity model was modified to house a porous floor with a vent chamber beneath the floor. The expectation was that for closed cavity flow the high-pressure air at the rear of the cavity would vent to the low-pressure region at the front of the cavity, causing the flowfield to switch to open cavity flow. This Note describes the results of an experimental investigation to determine the effectiveness of this passive venting system.

关键词： Drag Coefficient Pressure Coefficient Turbulent Boundary Layer Axisymmetric Flow Transonic Wind Tunnel Supersonic Speed Angle of Attack NASA Langley Research Center solution algorithm Skin Friction Drag

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ANALYSIS OF COMPLEX HYPERSONIC FLOWS WITH STRONG VISCOUS INVISCID INTERACTION

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AIAA JOURNAL 1988年第7期26卷 832-840页

作者： POWER, GD BARBER, TJ United Technologies Research Center East Hartford Connecticut

Two methods to improve the efficiency of predicting viscous/inviscid interaction in hypersonic flow are examined using an explicit full Navier-Stokes and a parabolized Navier-Stokes procedure. For the first method, a coarse grid full Navier-Stokes result is obtained that resolves the interaction effect of the viscous layer on the inviscid flowfield. In order to enhance the calculation of the surface normal gradients, the results of the coarse grid calculation are then used as initial and boundary conditions for another full Navier-Stokes calculation on a refined grid. Comparisons with benchmark experimental data indicate that this approach yields accurate skin friction and wall heat transfer at a substantially reduced computational cost compared to an initial fine grid calculation. The second method is based on a modification of a parabolized Navier-Stokes procedure to properly include upstream influence effects in the strong interaction region. In this approach, the stream wise pressure gradient term has been modified to account for the propagation of pressure waves within the subsonic layer through a global pressure iteration approach. Using this improved algorithm, good agreement with wall pressure, skin friction, and heat transfer is obtained compared with both experimental data and full Navier- Stokes results. The global pressure iteration scheme demonstrates a considerable reduction in computational time and memory requirements compared to the full Navier-Stokes procedure. © 1988 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.

关键词： Hypersonic Flows Skin Friction Accurate Heat Transfer Prediction Navier Stokes Calculations Boundary Layer Equations Adverse Pressure Gradient CFD Mach Numbers solution algorithm Shock Layers

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STABILIZATION OF COMPUTATIONAL PROCEDURES FOR CONSTRAINED DYNAMICAL-SYSTEMS

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1988年第4期11卷 365-370页

作者： PARK, KC CHIOU, JC UNIV COLORADO CTR SPACE STRUCT & CONTROLS BOULDER CO 80309 USA

A new stabilization method of treating constraints in multibody dynamical systems is presented. By tailoring a penalty form of the constraint equations, the method achieves stabilization without artificial damping and yields a companion matrix differential equation for the constraint forces;hence, the constraint forces are obtained by integrating the companion differential equation for the constraint forces in time. A principal feature of the method is that the errors committed in each constraint condition decay with its corresponding characteristic time scale associated with its constraint force. Numerical experiments indicate that the method yields a marked improvement over existing techniques. © 1988 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.

关键词： Holonomic Constraints solution algorithm Fluid Structure Interaction Robotic Manipulators Computing Large Space Structures Coriolis Force Satellites

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OPTIMIZED ROTATION-AXIS ATTITUDE MANEUVER CONTROLLER FOR THE SPACE-SHUTTLE ORBITER

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1987年第1期10卷 4-13页

作者： REDDING, DC ADAMS, NJ The Charles Stark Draper Laboratory Cambridge Massachusetts

This paper describes a controller for automatic attitude maneuvers of reaction-control-jet-equipped spacecraft. It is based on a new, real-time algorithm for solution of fuel-optimal maneuvers, assuming on-off control and linearized dynamics. These solutions provide efficient model trajectories that are easily tracked using a feed-forward, feedback controller structure. This approach was developed as a software upgrade to the Space Shuttle Orbiter on-orbit autopilot, for which it shows a very substantial performance benefit in a wide range of simulated maneuver tasks. © 1987 American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Space Shuttle Orbiter Autopilot Reaction Control System Earth Open Loop solution algorithm Roll Control Spacecraft Dynamics Spacecraft Control Numerical algorithms

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ADAPTIVE TRIANGULAR MESH GENERATION

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AIAA JOURNAL 1987年第10期25卷 1356-1364页

作者： ERLEBACHER, G EISEMAN, PR COLUMBIA UNIV DEPT APPL PHYS & NUCL ENGNNEW YORKNY 10027

A general adaptive algorithm is developed on triangular meshes. The adaptivity is provided by a combination of node addition, dynamic node connectivity and a simple node movement strategy. While the local restructuring process and the node addition mechanism take place in the physical plane, the nodes are displaced on a monitor surface, constructed from the salient features of the physical problem. An approximation to mean curvature detects changes in the direction of the monitor surface, and provides the pulling force on the nodes. solutions to the axisymmetric Grad-Shafranov equation demonstrate the capturing, by triangles, of the plasmavacuum interface in a free boundary equilibrium configuration. © 1987 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.

关键词： Mesh Generation solution algorithm Numerical algorithms Grad Shafranov Equation Parallel Processing (Computers) Hardware Development Compressible Flow Reacting Flow Taylor Series Magnetic Flux

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PARABOLIZED NAVIER-STOKES ANALYSIS OF DUCTED SUPERSONIC COMBUSTION PROBLEMS

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JOURNAL OF PROPULSION AND POWER 1987年第5期3卷 455-464页

作者： SINHA, N DASH, SM Science Applications International Corporation Princeton New Jersey

The extension of a recently developed implicit/explicit approach to analyzing two-dimensional ducted supersonic mixing problems with finite-rate chemistry is presented. The hybrid approach combines a fully implicit parabolic mixing algorithm, an explicit viscous-characteristic-based wave-solver algorithm, and a linearized implicit chemical kinetic solution algorithm. The resultant model provides spatial marching solutions of the parabolized Navier-Stokes (PNS) equations for supersonic combustion problems. Specialized procedures are incorporated to deal with the near-wall sublayer. A parabolic option is available that can be utilized in the direct or inverse mode for design applications. The ability of the model to treat shock waves and wave/mixing layer interactions is assessed via comparisons of predictions with those of well-established, explicit shock-capturing Euler (SCIPPY) and PNS (SCIPVIS) models. Applications to several supersonic combustion flowfield problems are presented that exhibit overall capabilities. © 1987 American Institute of Aeronautics and Astronautics, Inc.

关键词： Supersonic Combustion Mach Angle solution algorithm Combustors Turbulence Models Velocity Profiles Shear Layers Continuity Equation Skin Friction Coefficient Mach Number

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