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Sensitivity of mixed subsonic-supersonic turbulent mixing layers

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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Diffusion timescale of porous pressure-sensitive paint

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AIAA JOURNAL 2001年第12期39卷 2400-2402页

作者： Liu, TS Teduka, N Kameda, M Asai, K NASA Langley Res Ctr Model Syst Branch Hampton VA 23665 USA Tokyo Univ Agr & Technol Tokyo 1848588 Japan Natl Aerosp Lab Adv Measurement Technol Grp Tokyo 1828522 Japan

Diffusion timescale of porous pressure-sensitive paint (PSP) was presented. An expression was developed that illustrated the relationship between the diffusion timescale and the fractal dimension of the pores. Results showed that for every porous PSPs the classical square-law estimate of the diffusion timescale should be replaced by the generalized relation which was derived.

关键词： Pressure Sensitive Paint Expanding Nozzle Turbulence Models Porous Materials Jet Noise solution algorithm Military Aircraft Dynamic Analysis Pressure Sensors Compressibility

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Damping perturbation method for flutter solution:: The g-method

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AIAA JOURNAL 2000年第9期38卷 1519-1524页

作者： Chen, PC Zona Technol Inc Scottsdale AZ 85251 USA

By utilizing a damping perturbation method, the present g-method includes a first-order damping term in the flutter equation that is rigorously derived from the Laplace-domain aerodynamics. The g-method generalizes the K-method and the P-K method for reliable damping prediction. It Is valid in the entire reduced frequency domain and up to the first order of damping. The g-method utilizes a reduced-frequency sweep technique to search for the roots of the flutter solution and a predictor-corrector scheme to ensure the robustness of the sweep technique. The solution algorithm of the g-method is proven to be efficient and robust and can obtain an unlimited number of aerodynamic lag roots, as demonstrated by the results of the selected test cases.

关键词： Perturbation Method Aerodynamic Damping Frequency Domain solution algorithm Three Degrees of Freedom Sweptback Wings Aeroelastic Analysis Damping Matrix Fuselages Nastran

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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

A forward swept wing airplane has been considered to determine its structural dynamics and quasistatic aeroelastic equations of motion. It is seen that only one dynamic mode is required to achieve convergence because of the wide separation between the first and second modal frequencies, and that modal residualization is obviously more accurate than truncation.

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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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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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 engine governor model has been incorporated into the individual blade rotor model Hibrom for helicopter inverse simulation. The rotorspeed is now a degree of freedom within the modeled system. A series of modification has been made to the solution algorithm Genisa to accommodate the variation of rotorspeed. In particular, the control application interval is recalculated iteratively at each time step.

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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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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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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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

Eight years ago, Southampton initiated a program of research into the experimental application of distributed suction for the automatic control of boundary-layer transition. In addition to the experimental work, a complementary program of theoretical work was performed. This work was aimed at both modeling the experiments and extending the scope of the research by considering more suction panels and more realistic geometries. The resulting data was analyzed.

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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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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