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GRID GENERATION FOR 3-DIMENSIONAL TURBOMACHINERY GEOMETRIES INCLUDING TIP CLEARANCE

JOURNAL OF PROPULSION AND POWER 1993年第1期9卷 59-66页

作者： BASSON, AH KUNZ, RF LAKSHMINARAYANA, B PENN STATE UNIV DEPT AEROSP ENGNUNIV PKPA 16802

An efficient technique for the generation of structured grids for viscous flow computations in turbomachinery blade rows (two- and three-dimensional), and a specialized embedded H-grid for application, particularly to tip clearance flows, are presented. The grid generation technique uses a combination of algebraic and elliptic methods to obtain smooth grids while maintaining strict control over grid spacing and orthogonality at domain boundaries. A geometric series scheme is used to distribute boundary points. Algebraically generated layers next to boundaries are used, thus excluding highly clustered regions from the elliptic generation procedure's domain. The computational efficiency of the elliptic generation procedure is greatly enhanced by the application of the minimal residual method. The embedded H-grid topology provides good resolution of tip clearance effects. This topology requires only minor modifications to flow solvers developed for conventional H-grids. The results obtained with an embedded H-grid are compared to those obtained using a thin-tip approximation. A linear compressor cascade with tip clearance was used as a test case. Both grid topologies capture the dominant flow structures associated with the leakage flow. The embedded H -grid provided better quantitative agreement with the experimental results.

关键词： Turbomachine Blades Internal Flows Compressor Cascade Pressure Coefficient Poisson's Equation Vortex Structure Navier Stokes Solver Turbulence Models Aerospace Engineering solution algorithm

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LOCALLY IMPLICIT TOTAL VARIATION DIMINISHING SCHEMES ON MIXED QUADRILATERAL-TRIANGULAR MESHES

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AIAA JOURNAL 1993年第11期31卷 2008-2015页

作者： HWANG, CJ YANG, SY National Cheng Kung University Tainan Taiwan Republic of China

Locally implicit total variation diminishing schemes on mixed quadrilateral-triangular static/dynamic meshes have been developed to study steady and unsteady flows, respectively. In a Cartesian coordinate system, the Euler equations are solved by using a cell-centered finite volume algorithm. For steady inviscid flows, the efficiency and accuracy of the present approach are confirmed by investigating the oblique shock reflection at a wall and transonic flow around an NACA 0012 airfoil. To treat unsteady flow problems with moving boundaries, a new dynamic mesh algorithm, which saves memory, is efficient, and maintains quality, is presented in this paper. For analyzing the unsteady transonic flow around an NACA 0012 airfoil that pitches harmonically about the quarter chord, a quadrilateral-triangular dynamic mesh system is used. The calculated instantaneous pressure distributions and lift and moment coefficients during a cycle of motion compare well with related numerical and experimental data.

关键词： Total Variation Diminishing NACA 0012 Unsteady Transonic Flow Oblique Shock Euler Equations Cartesian Coordinate System Lift Coefficient Freestream Mach Number Pressure Coefficient solution algorithm

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SPATIAL ADAPTATION OF UNSTRUCTURED MESHES FOR UNSTEADY AERODYNAMIC FLOW COMPUTATIONS

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AIAA JOURNAL 1992年第5期30卷 1243-1251页

作者： RAUSCH, RD BATINA, JT YANG, HTY NASA LANGLEY RES CTRUNSTEADY AERODYNAM BRANCHDIV STRUCT DYNAMHAMPTONVA 23665 PURDUE UNIV SCH ENGNW LAFAYETTEIN 47907

Spatial adaptation procedures for the accurate and efficient solution of steady and unsteady inviscid flow problems are described. The adaptation procedures were developed and implemented within a two-dimensional unstructured-grid upwind-type Euler code. These procedures involve mesh enrichment and mesh coarsening to either add points in high gradient regions of the flow or remove points where they are not needed, respectively, to produce solutions of high spatial accuracy at minimal computational cost. The paper describes a new approach to detect high gradient regions of the flow that uses the substantial derivative of density. Additionally, the paper gives a detailed description of the enrichment and coarsening procedures and further describes a new weighted averaging procedure and the interpolation of flow variables that improves the overall accuracy of the flow solver. Presented are comparisons with alternative results and experimental data to provide an assessment of the accuracy and efficiency of the capability. Steady and unsteady transonic results, obtained using spatial adaptation for the NACA 0012 airfoil, are shown to be of high spatial accuracy, primarily in that the shock waves are very sharply captured. The results were obtained with large computational savings when compared to results for a globally enriched mesh with cells subdivided as many times as the finest cells of the adapted grid.

关键词： Aerodynamic Flows Shock Waves Pitching Airfoil Unstructured Grid Compressibility solution algorithm Conservation Equations Courant Friedrichs Lewy Lagrange Multipliers Stagnation Point

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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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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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HIGHER-ORDER EIGENPAIR PERTURBATIONS

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AIAA JOURNAL 1992年第7期30卷 1870-1876页

作者： ELDRED, MS LERNER, PB ANDERSON, WJ LOS ALAMOS NATL LAB LOS ALAMOSNM 87544

A matrix method is presented for the exact calculation of large eigenpair perturbations arising from design variable changes. The method is "forward analysis" in the sense that design variable changes are known and eigenpair perturbations are computed. Competing methods for forward analysis include reanalysis and first-order approximate methods. First-order methods are well known for their ability to calculate small eigenpair changes but are inadequate when large changes are required. In this paper, a new method of forward analysis is presented that takes into account all orders of the perturbation expansion. A benchmark cantilever beam will be analyzed with the new method for large perturbations in design variables. The method will be valuable for fast reanalysis and for identification and model correlation studies where sizeable differences exist between a baseline model and an objective model.

关键词： Cantilever Beam Finite Element Analysis Perturbation Method Structural Dynamics solution algorithm Iterative solution Bending Stiffness Nonlinear Systems Catalysts Nastran

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MULTIZONAL NAVIER-STOKES solutionS FOR THE MULTIBODY SPACE-SHUTTLE CONFIGURATION

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JOURNAL OF SPACECRAFT AND ROCKETS 1992年第1期29卷 129-137页

作者： CHEN, CL RAMAKRISHNAN, S SZEMA, KY DRESSER, HS RAJAGOPAL, K ROCKWELL INT CORP DIV SPACEDOWNEYCA 90241

Numerical simulation of flow past the multibody Shuttle configuration in ascent mode has been carried out using the USA (unified solution algorithms) code, which is a finite volume, unified time/space marching, zonal, Reynolds-averaged Navier-Stokes solver featuring an implicit, upwind-biased scheme and total variation diminishing discretization for high accuracy. Body conforming elliptic multizonal grids were used in the computation. The agreement between computed and experimental results is reasonable. The interference effects of various components on the surface pressure distribution are discussed. The results show the importance of ensuring simulation of proper blockages due to various components of the mated Space Shuttle vehicle to obtain a reliable prediction of aerodynamic forces. Agreement between computed and experimental results could be improved by refining the definition of various geometric features and by including all geometric complexities.

关键词： Space Shuttle Total Variation Diminishing Reynolds Averaged Navier Stokes Freestream Conditions solution algorithm Solid Rocket Boosters Roe Approximate Riemann Solver Flight Testing Wind Tunnel Walls Turbulent Boundary Layer

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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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HELICOPTER ROTOR BLADE AEROELASTICITY IN FORWARD FLIGHT WITH AN IMPLICIT STRUCTURAL FORMULATION

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AIAA JOURNAL 1992年第9期30卷 2274-2282页

作者： CELI, R University of Maryland College Park Maryland 20742

This paper describes an aeroelastic stability and response analysis in which the structural operator is formulated numerically, without expanding analytically the various algebraic expressions that make up the beam model. No ordering schemes need to be invoked to simplify the algebraic manipulations, and the various components of the mathematical model of the beam can be implemented and modified independently. The formulation is compatible with most solution algorithms. Two different implicit formulations are presented. The results of four illustrative examples are also presented. The first focuses on the effects of higher order kinematic nonlinearities on the aeroelastic stability and response of a hingeless rotor blade. The remaining three show how to introduce, using the implicit formulation, a nonlinear stress-strain relation in table look-up form, a composite cross section, and cross-sectional warping. Aeroelastic stability results are presented for all examples.

关键词： Aeroelastic Stability Helicopter Rotor Bernoulli Euler Beams Stress Strain Curve Hingeless Rotor Blade Composite Materials Mathematical Models Rotary Wing Elastic Deformation solution algorithm

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OPTIMAL OUTPUT-FEEDBACK FOR LINEAR TIME-PERIODIC SYSTEMS

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1992年第2期15卷 416-423页

作者： CALISE, AJ WASIKOWSKI, ME SCHRAGE, DP Georgia Institute of Technology Atlanta Georgia 30332

An approach is developed for applying optimal output feedback control theory to the design of fixed gain controllers for lime-periodic systems. Constant feedback gains based on plant outputs are calculated by minimizing a linear quadratic performance cost functional. A solution algorithm is developed using Floquet-Lyapunov theory and a generalized harmonic expansion technique. The theory is applied to the control of a helicopter rotor blade in forward flight through individual blade control. It is shown that constant gain output feedback can be used to augment the stability of the resulting time-periodic system, with the potential for greatly reducing the implementation complexity.

关键词： Full State Feedback Helicopter Blade solution algorithm Linear Time Invariant System Linear Quadratic Gaussian Numerical Integration Aeroelastic Stability Damping Ratio Angle of Attack Rotor Blades

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