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

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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INTERFERENCE FLOWS PAST CYLINDER-FIN-STING-CAVITY ASSEMBLIES

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JOURNAL OF AIRCRAFT 1992年第2期29卷 194-202页

作者： BAYSAL, O FOULADI, K LEUNG, RW SHEFTIC, JS Old Dominion University NorfolkVirginia 23529 Lockheed Missiles and Space Company Inc. SunnyvaleCalifornia 94089

A computer code, VISCC, is developed to solve the three-dimensional, Reynolds-averaged, unsteady, compressible, and complete Navier-Stokes equations. The equations are solved by an implicit, fully vectorized, finite-volume, upwind-biased, approximately factored, and multigrid method. A hybrid domain decomposition method is developed to utilize the combined advantages of overlapped grids, zonal grids, and block-structured grids. An algebraic turbulence model is developed to represent the Reynolds stresses. The store considered here for simulation is a missile configuration with four tail fins and an L-shaped offset sting. The missile is placed first directly above the opening of a rectangular box cavity, then submerged completely inside the cavity. These two cases represent two distinct and important interference characteristics for an internal store carriage and a subsequent separation. The freestream Mach and the unit Reynolds numbers are 2.75 and 2.97 million per foot, respectively. The results of the time-accurate computations depict these complex flows and help understanding the interference effects between the store and the cavity. These effects are more pronounced when the store is placed inside the parent body. The time-averaged surface pressures compare well with the wind-tunnel data.

关键词： Boundary Layer Thickness Aerodynamic Simulation Supersonic Flow Wind Tunnel Tests Pressure Coefficient Vortex Shedding Navier Stokes Equations solution algorithm Inviscid Flow Equations Flight Testing

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ADMISSIBLE LARGE PERTURBATIONS IN STRUCTURAL REDESIGN

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AIAA JOURNAL 1991年第1期29卷 104-113页

作者： BERNITSAS, MM KANG, B University of Michigan Ann Arbor Michigan 48109

A new algorithm for structural redesign by perturbation is developed. It allows for large changes between baseline and objective structures and can satisfy both modal and static displacement objectives. It is faster and more accurate than previously developed pertubation resizing methods because it advances incrementally to the objective structure using large admissible perturbations. The computer code developed is used as postprocessor to general or special purpose finite element codes, to improve upon the design of structures with unacceptable modal and/or static displacement response. Depending on the relation between the number of redesign goals, allowable structural changes, and admissibility constraints, the desired redesign may be feasible-either locally optimal or unique-or may not exist. In the latter case, a minimum-error inadmissible design is produced. Several numerical examples are used to study the effects of definition and relaxation of the redesign admissible domain and demonstrate the accuracy of the new redesign algorithm. An offshore tower with repeated eigen-values and 192 degrees of freedom is also redesigned subject to frequency, static displacement goals, and admissibility constraints.

关键词： Finite Element Analysis Nastran Hinged Beam Fluid Structure Interaction Perturbation Method Structural Design Structural Response Young's Modulus Quadratic Programming solution algorithm

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PRIMITIVE VARIABLE, STRONGLY IMPLICIT CALCULATION PROCEDURE FOR VISCOUS FLOWS AT ALL SPEEDS

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AIAA JOURNAL 1991年第8期29卷 1241-1249页

作者： CHEN, KH PLETCHER, RH IOWA STATE UNIV SCI & TECHNOL DEPT MECH ENGNAMESIA 50011 IOWA STATE UNIV SCI & TECHNOL CTR COMPUTAT FLUID DYNAMAMESIA 50011

A coupled solution procedure is described for solving the compressible form of the time-dependent, two-dimensional Navier-Stokes equations in body-fitted curvilinear coordinates. This approach employs the strong conservation form of the governing equations but uses primitive variables (u, v, p, T) rather than the more traditional conservative variables (rho, rho-u, rho-v, e(t)) as unknowns. A coupled modified strongly implicit procedure (CMSIP) is used to efficiently solve the Newton-linearized algebraic equations. It appears that this procedure is effective for Mach numbers ranging from the incompressible limit (M is-proportional-to approximately 0.01) to supersonic. Generally, smoothing was not needed to control spatial oscillations in pressure for subsonic flows despite the use of central differences. Dual-time stepping was found to further accelerate convergence for steady flows. Sample calculations, including steady and unsteady low-Mach-number internal and external flows and a steady shock-boundary-layer interaction flow, illustrate the capability of the present solution algorithm.

关键词： Continuity Equation Incompressible Flow Freestream Mach Number Navier Stokes Calculations solution algorithm Curvilinear Coordinates Strouhal Number Nusselt Number Wall Temperature Pressure Coefficient

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Numerical Modeling of Heat-Pipe Transients

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 1991年第3期5卷 374-379页

作者： Bowman, W. Jerry USAF Acad HQ USAFA DFAN Colorado Springs CO 80840 USA

This paper describes work done to increase the understanding of numerical modeling of heat-pipe transients. The most significant contribution discussed in the paper is a method of reducing the amount of computer time required to obtain a numerical solution. It was found that time-accurate results could be obtained even if the heat-pipe's wall model and the heat-pipe's vapor model use different time steps to march through time. This leads to a reduction in computer time requirements by as much as a factor of 500. A second method of decreasing computer time requirements is also discussed. The method involves using an implicit solution algorithm instead of the explicit method used for most of this work. The implicit method was at least 10 times faster than the explicit method. Also in the paper, two different methods for modeling the heat-pipe wall transient are discussed and compared. Both methods gave comparable results;however, one method required less computer time than the other.

关键词： Numerical Stability Heat Pipes solution algorithm Thermal Diffusivity Condenser Thermocouples Condensation Friction Coefficient Normal Stress Data Acquisition System

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STRUCTURAL MODEL CORRELATION USING LARGE ADMISSIBLE PERTURBATIONS IN COGNATE SPACE

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AIAA JOURNAL 1991年第12期29卷 2222-2232页

作者： BERNITSAS, MM TAWEKAL, RL University of Michigan Ann Arbor Michigan 48109

A nonlinear perturbation method is developed to solve the problem of correlating a finite element model (FEM) to a structure for which an incomplete set of natural frequencies and mode shapes and/or some static deflections have been measured. The solution algorithm can handle differences between FEM and structure, in design variables and response, as large as 100-300%, depending on the scale of the structure and correlation measures. This is achieved incrementally by making inadmissible predictions, identifying the modal cognate space relevant to the correlation measures, and making admissible corrections in the cognate space. The developed computer code postprocesses results of the FEM modal and/or static analyses of the initial model only. No additional finite element analysis is required. Lagrange multipliers reveal the dominant correlation requirements and the active admissible cognate subspace. Depending on the number of correlation variables and measures, an optimal, a unique, or an inadmissible minimal error solution may be produced. Beam and offshore tower examples are used to lest the algorithm and investigate conflicting requirements, definition of admissible cognate space, limits of allowable differences between FEM and structure, accuracy, and cost of the nonlinear perturbation method.

关键词： Structural Modeling Finite Element Analysis Lagrange Multipliers Perturbation Method solution algorithm Nastran Structural Element Mathematical Models Dynamic Response Computing

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VORTICAL FLOW solutionS USING A TIME-LAGGED, THIN-LAYER, NAVIER-STOKES algorithm

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AIAA JOURNAL 1991年第6期29卷 876-877页

作者： MOUNTS, JS BELK, DM MILTON, JE USAF ARMAMENT LABAERODYNAM BRANCHEGLIN AFBFL 32542 UNIV FLORIDA CTR GRAD ENGNEGLIN AFBFL

A PROVEN inviscid algorithm (Program EAGLE - Flow Solver) 1-3 has been modified to use the flux-difference split scheme of Roe 4 to solve the time-lagged, thin-layer approximation to the Navier-Stokes equations. 5,6 Calculations are presented evaluating the ability of the time-lagged, thin-layer Navier-Stokes algorithm to obtain transonic solutions for lifting bodies at incidence angles sufficient for the flow to be dominated by large-scale free vortices in the leeside flowfield.

关键词： Navier Stokes algorithm Vortex Sheet Navier Stokes Calculations Lifting Body Turbulence Models Turbulent Flow Aerodynamics solution algorithm Euler Equations Computing

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UNSTEADY EULER algorithm WITH UNSTRUCTURED DYNAMIC MESH FOR COMPLEX-AIRCRAFT AERODYNAMIC ANALYSIS

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AIAA JOURNAL 1991年第3期29卷 327-333页

作者： BATINA, JT NASA Langley Research Center Hampton Virginia 23665

An Euler solution algorithm is presented for unsteady aerodynamic analysis of complex-aircraft configurations. The flow solver involves a multistage Runge-Kutta time-stepping scheme that uses a finite-volume spatial discretization on an unstructured grid made up of tetrahedra. A significant contribution of the research is the development and implementation of a moving mesh algorithm that is employed for problems involving static or dynamic deformation of the aircraft. The mesh algorithm is a general procedure that can treat realistic motions and deformations of complex-aircraft configurations. Steady and unsteady results are presented for a supersonic fighter configuration to demonstrate applications of the Euler solver and dynamic mesh algorithm. The unsteady flow results were obtained for the aircraft oscillating harmonically in a complete-vehicle bending mode. Effects of angle of attack and reduced frequency on instantaneous pressures and force responses were investigated. The paper presents descriptions of the Euler solver and dynamic mesh algorithm along with results that assess the capability.

关键词： Boeing 747 Lift Coefficient Aircraft Configurations Unstructured Grid Flow Conditions Unsteady Aerodynamic Analysis solution algorithm Aerodynamic Simulation Euler Equations Canard

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DETERMINING A FORCE ACTING ON A PLATE - AN INVERSE PROBLEM

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AIAA JOURNAL 1991年第3期29卷 464-470页

作者： DCRUZ, J CRISP, JDC RYALL, TG DEF SCI & TECHNOL ORG AERONAUT RES LABDIV AIRCRAFT STRUCTMELBOURNEVIC 3001AUSTRALIA

It is traditional in the study of elasticity to determine the response of a structure to a known force. Such problems may be described as direct problems as they involve the determination of the unknown effects of a known cause. The problem of determining the force acting on a structure from measurements of the response of the structure to the force is the inverse problem. Presented here is a method for determining the location and magnitude of a static point force acting on a simply-supported elastic rectangular plate from a number of displacement readings at discrete points on the plate. This problem reduces to a nonlinear least-squares one. It is solved by calculating an approximate solution from a simplified set of equations that is then used as an initial estimate in an iterative procedure for a solution of the actual nonlinear least-squares problem. Results of numerical simulations illustrate the use of the method, and a confidence criterion is supplied. Presented also is a demonstration of the robustness of the algorithm to the effects of measurement noise, as well as a means by which the method may be extended to problems of a more general nature.

关键词： Inverse Problems Numerical Simulation Poisson's Ratio Finite Element Formulation Aspect Ratio Newton's Method Electromagnetic Radiation solution algorithm Aircraft Structures Aerodynamic Force

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PROBABILITY DENSITY-FUNCTION APPROACH FOR MULTIDIMENSIONAL TURBULENT-FLOW CALCULATIONS WITH APPLICATION TO IN-CYLINDER FLOWS IN RECIPROCATING-ENGINES

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AIAA JOURNAL 1991年第2期29卷 208-218页

作者： HAWORTH, DC ELTAHRY, SH General Motors Research Laboratories Warren Michigan 48090

The probability density function (pdf) method is extended to two- and three-dimensional transient turbulent flows. The numerical approach couples a Lagrangian Monte Carlo method to solve for the joint pdf of velocity and scalar compositions with an Eulerian finite-volume algorithm to calculate mean pressure and a turbulence time scale. A general approach applicable to variable-density chemically reacting flows has been taken;the present results are for nearly uniform density inert flows. Three engine-like configurations have been investigated: 1) a noncompressing axisymmetric cylinder-piston assembly with a central port;2) a noncompressing axisymmetric cylinder-piston assembly with an annular port;and 3) a compressing three-dimensional configuration with an off-center valve. Pdf results are compared with measurements and with conventional k-epsilon calculations for the two axisymmetric geometries. For these noncompressing flows the pdf approach is found to have little advantage over a k-epsilon model. Mean velocity profiles from both models are in good agreement with experiment for the central port case, whereas agreement for the annular port is less satisfying. Root-mean-square axial velocities from both models are low at early times in the intake process, but improve later in the cycle. Influence of numerical parameters on solution accuracy is assessed. The present work confirms the feasibility of the pdf approach for complex turbulent flows and represents an intermediate step in the application of pdf methods to multidimensional turbulent reacting flows, where they are expected to offer their greatest advantage.

关键词： Reciprocating Engine Kinematic Viscosity Axisymmetric Flow Monte Carlo Method Chemically Reacting Flow Reynolds Stress Kinetic Energy Turbulence Models Number of Particles solution algorithm

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