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Unstructured method for flows past bodies in general three-dimensional relative motion

AIAA JOURNAL 2001年第2期39卷 219-224页

作者： Singh, KP Baysal, O Old Dominion Univ Dept Aerosp Engn Norfolk VA 23529 USA Old Dominion Univ Coll Engn & Technol Norfolk VA 23529 USA

A three-dimensional methodology was developed for unsteady flows past bodies that are in relative motion and where the trajectory of the motion was determined from the instantaneous aerodynamic field. This method coupled the equations of fluid flow and those of rigid-body dynamics and then captured the unsteady aerodynamic interference between the stationary and moving boundaries. The time-dependent, compressible Euler equations were solved on dynamic, unstructured meshes by an explicit, finite volume, and upwind method. The grid adaptation was performed within a window placed around a moving body, The Euler equations of dynamics were then solved by a Runge-Kutta integration scheme. The flow solver and the adaptation scheme were validated by simulating the transonic, unsteady flow around a wing undergoing a forced, periodic pitching motion and then comparing the results with the experimental data. Finally, the overall methodology was demonstrated by simulating the unsteady flowfield and the trajectory of a store dropped from a wing, The methodology, with its computational cost notwithstanding, has proven to be accurate, automated, easy for dynamic gridding, and relatively efficient for the required work hours.

关键词： Aerodynamic Interference Six Degree of Freedom Euler Equations Runge Kutta Integration Rectangular Wing NACA 64A010 Wing Root Domain Decomposition Methods solution algorithm Angle of Attack

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Sensitivity of mixed subsonic-supersonic turbulent mixing layers

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JOURNAL OF PROPULSION AND POWER 2001年第4期17卷 823-835页

作者： Cottrell, DC Plesniak, MW Purdue Univ Sch Mech Engn Maurice J Zucrow Labs W Lafayette IN 47907 USA

Numerical predictions of compressible turbulent mixing layers have been performed for convective Mach numbers up to 0.7 (M-C less than or equal to0.7), This flow is particularly challenging to compute because the mixing layer consists of one supersonic stream and one subsonic stream, resulting in a mixed hyperbolic/elliptic solution. The FLUENT (C) computational fluid dynamics code, which incorporates a renormalization group k-is an element of turbulence model and the SIMPLEC solution algorithm, was used to perform the computations. Initially, predictions were performed for several different convective Mach numbers (M-C = 0.2, 0.5, and 0.7), and the computed results (mixing layer thickness, mean velocity, and turbulence parameters) were compared with experiments to benchmark the code. Following this qualification procedure, the sensitivity of the Me = 0.7 case to disturbances was further investigated by introducing small perturbations to the boundary conditions and recomputing the mixing layer. Specifically, effects of perturbations to the secondary stream stagnation pressure and test section wall adjustment angle were investigated, It was found that the compressible mixing layer growth rate was significantly altered by small changes (<4%) in the secondary stream stagnation pressure. In addition, divergence or convergence of the test section walls of less than 3 deg resulted in appreciable changes in the streamwise pressure gradient and mixing layer development.

关键词： Turbulent Mixing Adverse Pressure Gradient SIMPLE algorithm Kinematic Viscosity Freestream Velocity Kinetic Energy Stress Distribution solution algorithm Turbulence Models Turbulent Boundary Layer

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Unified formulation for compressible-incompressible flow simulation with mesh adaptation

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AIAA JOURNAL 2001年第12期39卷 2425-2427页

作者： Turgeon, É Pelletier, D Ecole Polytech Dept Genie Mech Montreal PQ H3C 3A7 Canada

Proposes a pressure-based formulation capable of handling compressible and incompressible flows. Temperature dependence of air properties; Role of absolute pressure and pressure differences; Application of a standard ... 详细信息

关键词： Incompressible Flow Freestream Conditions Neumann Boundary Condition Skin Friction Apparent Viscosity Compressibility Effect Continuity Equation Wall Temperature Thermal Conductivity solution algorithm

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Unstructured grid arbitrarily shaped element method for fluid flow simulation

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AIAA JOURNAL 2000年第12期38卷 2246-2252页

作者： Lai, YG Univ Iowa Iowa Inst Hydraul Res Iowa City IA 52242 USA

A three-dimensional unstructured grid arbitrarily shaped element method is developed for solving the Navier-Stokes equations. The proposed method is generally applicable to arbitrarily shaped elements and, thus, offers the potential to unify many of the different grid topologies into a single formulation Examples of grid topologies include a structured hexahedral mesh;unstructured tetrahedral mesh;hybrid mesh using a combination of hexahedra, tetrahedra, prisms, and pyramids;Cartesian mesh with elements (cubes) cut by now boundaries;and mixed arbitrary multiblock meshes. The concept of such an arbitrary element method is developed and implemented into a pressure-based finite volume solver. It utilizes a collocated and cell-centered storage scheme. Expressions for second-order discretizatious of the convection and diffusion terms are derived and presented for an arbitrarily shaped element. The developed code, as a first step, is applied to two selected three dimensional viscous flows using a structured hexahedral mesh and an unstructured tetrahedral mesh. It is demonstrated that the concept of the arbitrarily shaped element method can be viable and efficient.

关键词： Unstructured Grid Fluid Flow Navier Stokes Equations Peclet Number Tetrahedral Element solution algorithm Radial Velocity Convection Diffusion Equation Conservation Equations Predictor Corrector Method

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Attitude feedback control: Unconstrained and nonholonomic constrained cases

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2000年第4期23卷 657-664页

作者： Aicardi, M Cannata, G Casalino, G Univ Genoa Dept Commun Comp & Syst Sci DIST I-16145 Genoa Italy

The problem is considered of asymptotically driving, the attitude of a spacecraft via feedback control. First, a simple feedback control structure based on the measure of the equivalent angle axis is determined for a fully actuated system. Then, the same reasoning is used to find the solution for a spacecraft operating in failure mode, that is, whenever the angular velocity vector is constrained to lie in one of the spacecraft's coordinate planes. The basic aim is to show that with a simple choice for the attitude parameterization, a simple and effective structure for the feedback control law can be obtained.

关键词： Feedback Control Closed Loop Control Spacecraft Attitude Attitude Control Quaternions solution algorithm Nonlinear Control

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Structural dynamics and quasistatic aeroelastic equations of motion

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JOURNAL OF AIRCRAFT 2000年第3期37卷 538-542页

作者： Dykman, JR Rodden, WP Boeing Co Long Beach CA 90807 USA

Presents information on a study which focused on the structural dynamics and the quasistatic aeroelastic equations of motions of a flight vehicle. Residualization of the aeroelastic equations of motion; Coefficients f... 详细信息

关键词： Structural Dynamics Stability Derivatives Aeroplane Canard Forward Swept Wing Angle of Attack Six Degree of Freedom solution algorithm Frequency Domain Control Surfaces

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Modification of a helicopter inverse simulation to include an enhanced rotor model

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JOURNAL OF AIRCRAFT 2000年第3期37卷 536-538页

作者： Doyle, SA Thomson, DG Univ Glasgow Dept Aerosp Engn Glasgow G12 8QQ Lanark Scotland

An individual blade rotor model has been developed at the University of Glasgow by Rutherford and Thomson (1997) for use in helicopter inverse simulation. In the context of helicopter flight dynamics, an inverse simulation generates the control time histories for the modeled helicopter performing a defined task. To implement such a model in an inverse sense, it is necessary to adopt a numerical integration technique similar to that proposed by Hess et al. (1991). The generic inverse simulation algorithm (Genisa) used by Rutherford and Thomson is essentially a modification of that documented by Hess et al. and is driven by specified maneuver constraints. The helicopter individual blade rotor model (Hibrom) represents the state of the art in helicopter inverse simulation. Among some of the simplifying assumptions made in its development was the assumption of constant rotor speed. This degree of freedom has a direct influence on the dynamic behavior of the main rotor, and its inclusion must be achieved before other modeling features, such as lead/lag freedom, can be incorporated. This paper describes modifications made to the inverse algorithm Genisa that allow the rotor-speed degree of freedom to be incorporated within Hibrom. An engine governor model was successfully incorporated into Hibrom for helicopter inverse simulation. Hence, the rotor speed is now a degree of freedom within the modeled system. The addition of the rotor-speed degree of freedom does not significantly affect the predicted control time histories for the maneuver considered in this study. However, as the boundaries of the flight envelope are approached, it may be expected that the enhanced rotor model will be closer to predicting actual flight behavior. (AIAA)

关键词： Helicopters Numerical Integration Aerodynamic Force Aerospace Engineering Nonlinear Systems Six Degree of Freedom Trailing Edge Flap solution algorithm Dynamic Response Frequency Domain

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Numerical optimization of the suction distribution for laminar flow control

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AIAA JOURNAL 2000年第2期38卷 370-372页

作者： Tutty, OR Hackenberg, P Nelson, PA Univ Southampton Sch Engn Sci Southampton SO17 1BJ Hants England Univ Southampton Inst Sound & Vibrat Res Southampton SO17 1BJ Hants England

Deals with a study on aerodynamics which developed an algorithm to solve the numerical optimization problem in suction distribution for laminar flow control. Flat plate configuration; Plate with pressure gradient; Con... 详细信息

关键词： Numerical Optimization Laminar Flow Freestream Velocity Adverse Pressure Gradient Freestream Turbulence solution algorithm Operating Costs NACA Airfoil Wind Tunnels Vortices

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Numerical investigation of installation effects in turbofan engines

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JOURNAL OF PROPULSION AND POWER 2000年第4期16卷 697-704页

作者： Joo, WC Yonsei Univ Dept Mech Engn Seoul 120749 South Korea

One of the important issues in the assessment of intake/engine compatibility in civil turbofan engines is the prediction of the coupling effects between the intake and the engine. An actuator-disk model has been applied to the calculations of the flow through a high-bypass-ratio turbofan geometry, including the presence of the core-support pylon and a nonaxisymmetric inlet, and the effects of the core engine. The results of a series of calculations are presented, and the nature of the interactions between the flow through a fan and the system components is addressed.

关键词： Turbofan Engines Reynolds Averaged Navier Stokes Bypass Ratio Static Pressure Cylindrical Coordinate System Numerical Modeling Blade Pitch Boundary Layer Thickness solution algorithm Shear Stress

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Two-timescale-integration method for inverse simulation

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1999年第3期22卷 395-401页

作者： Avanzini, G de Matteis, G de Socio, LM Politecn Torino Dept Aerosp Engn I-10129 Turin Italy Univ Roma La Sapienza Dept Mech & Aeronaut I-00184 Rome Italy

The integration method is extensively applied in the inverse simulation of aircraft motion where control inputs are determined once a maneuver or flight task is assigned. In many circumstances the presence of multiple timescales and right half-plane transmission zeros in aircraft dynamics introduces problems of accuracy and stability in the numerical algorithm. This paper presents a formulation for inverse simulation problems where the concept of timescale separation is merged into an integration technique and a constrained optimization method. Two subscale problems are solved separately for the slow and fast timescales and a numerical algorithm is devised that presents significant advantages in terms of numerical efficiency and robustness. The technique accounts for the issue of control saturation and lends itself to applications where the aircraft trajectory is given as a function of time. The results of the study show the improved performances of the technique in comparison with an integration method that is based on the local optimization concept.

关键词： Roll Control Inverse Problems Stability and Control Augmentation System Aerodynamic Moments Helicopters Numerical Integration solution algorithm Angle of Attack Sideslip Angle Aileron Roll

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