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Navier-Stokes computations for body/cruciform grid fin configuration

JOURNAL OF SPACECRAFT AND ROCKETS 2003年第1期40卷 30-38页

作者： Lin, H Huang, JC Chieng, CC Chung Shan Inst Sci & Technol Lung Tan 325 Peoples R China Natl Tsing Hua Univ Dept Engn & Syst Sci Hsinchu 300 Taiwan

A grid fin is an unconventional aerodynamic lifting and control device consisting of an outer frame with internal grid framework of small chord. The present study performs the Navier-Stokes computations of turbulent flows past 1) a grid fin alone and 2) fin/body combination shapes at Mach numbers of 2.5 and 0.7. This work designs a procedure to generate a structure grid with a simple and efficient algorithm combining "block-off" and "multiblock" methods for the complex configurations. Full Navier-Stokes equations with a pointwise version of the Baldwin-Barth one-equation turbulence model are discretized into finite difference form and solved by an algorithm in a fully coupled, implicit, and large block structure, and the solution algorithm achieves satisfactory convergence. The comparisons between computations and experimental data are made, and the detailed flow structure near grid fins can be obtained and examined.

关键词： Aerodynamic Characteristics Turbulence Models Navier Stokes Simulation Grid Fin solution algorithm Angle of Attack Bending Moment Eddy Viscosity Total Variation Diminishing Triangular Element

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Effect of Insulations and Coatings on Hypersonic Heat Flux Reconstruction

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 2021年第1期35卷 63-79页

作者： Nguyen, Nhat M. Ruda, Mathew L. Massa, Luca Virginia Polytech Inst & State Univ Kevin T Crofton Dept Aerosp & Ocean Engn 460 Old Turner St Blacksburg VA 24061 USA

The present study investigates the effects of material discontinuities and thermal resistances on the temperature reconstruction and heat flux evaluation via an inverse heat transfer method in hypersonic wind-tunnel tests. Thin coating layers and adhesive interfaces support a localized multidimensional temperature perturbation that alters the near-surface field. A technique is developed for the real-time evaluation of the heat transfer based on approximating the Green's function of the heat conduction equation in bounded complex domains and resolving the heat flux on a B-spline basis, leading to an efficient and robust algorithm. Evaluating the Green's function for three-dimensional problems with material discontinuities is generally difficult. A new approach is developed in which the Green's function is evaluated independently for the regular partitions of the domain, and appropriate connection conditions are derived to determine the full "system" Green's function. This paper describes the verification, validation, and application of the approach to the heat flux reconstruction for a nonaxisymmetric flat-faced article with coating and potting interfaces. The article was tested at Mach 6 in the Virginia Tech Hypersonic wind tunnel using four temperature sensors arranged in a cross pattern on the flat face. Good agreement was obtained between computational fluid dynamics predictions and the heat flux deduced from the experiments using the new data analysis method.

关键词： Heat Flux Distribution Green's Function Inverse Heat Conduction Hypersonic Wind Tunnels Heat Flow CFD Simulation Temperature Sensors Conduction Equation solution algorithm Data Analysis

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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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Damped oscillations of a liquid/gas surface upon step reduction in gravity

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JOURNAL OF SPACECRAFT AND ROCKETS 1997年第1期34卷 110-117页

作者： Wolk, G Dreyer, M Rath, HJ Weislogel, MM NASA LEWIS RES CTRMICROGRAV FLUIDS BRANCHCLEVELANDOH 44135

The reorientation and settling of a liquid/gas interface in a right circular cylinder upon step reduction in gravity is investigated numerically. A modified dynamic contact angle boundary condition is implemented where the hysteresis parameter gamma is employed as an adjustable parameter representing the degree of relative slip at the contact line. The effect of the boundary condition on the axial interface oscillation is studied and the dependence thereon of the resonant frequency and settling time is given. Results are shown regarding the behavior of the dynamic contact angle and the penetration of the surface oscillations into the bulk liquid. The numerical results are tuned via comparisons with existing experimental data, and a method for estimating the appropriate boundary condition providing good agreement is suggested. An accompanying scale analysis depicts gamma as a function of the Ohnesorge number, the cylinder radius, and the static contact angle, These independent parameters are measures of the system damping, characteristic surface deflection, and effective stiffness of the interface, Applications of the results may be made to spacecraft fluids management and the use of spacecraft and/or drop towers for fluids experimentation.

关键词： Ohnesorge Numbers Hysteresis Resonant Frequencies Capillary Number Surface Tension Navier Stokes Equations solution algorithm Propellant Linear Interpolation Numerical Analysis

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Calculation of multidimensional flames using large chemical kinetics

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AIAA JOURNAL 2008年第7期46卷 1640-1650页

作者： Katta, Viswanath R. Roquemore, William M. Innovat Sci Solut Inc Dayton OH 45440 USA USAF Res Lab Wright Patterson Air Force Base Propuls Directorate Wright Patterson AFB OH 45433 USA

A time-dependent, two-dimensional, detailed-chemistry computational fluid dynamics model, known as UNICORN (unsteady ignition and combustion using reactions), is used for solving complex flame problems. The unique features incorporated in UNICORN for handling extremely large chemical kinetics with ease and efficiency are discussed. A submixture concept that is used for evaluating transport properties is described. This concept increases the computational speed by a factor of five for a 208-species mechanism and is expected to have even higher efficiency with larger mechanisms. An implicit treatment for certain reaction-rate terms applied during the solution of species-conservation equations is described. Moving the reaction-rate source terms to the left-hand side of the partial differential equations eases the stiffness problem that is typically associated with combustion chemical kinetics. Computational speeds are further improved in UNICORN by completely integrating the chemical-kinetics mechanisms with the solution algorithm. A software-generated computational fluid dynamics approach is used to avoid the tedious and near-impossible task of manually integrating a large chemical-kinetics mechanism into a computational fluid dynamics code. Several calculations demonstrating the abilities of the UNICORN code are presented. Chemical-kinetics mechanisms up to 366 species and 3700 reaction steps are incorporated, and simulations for unsteady multidimensional flames are performed on personal computers. Making use of the robustness and efficiency of the UNICORN code, detailed chemical mechanisms developed for JP-8 fuel are tested for their accuracy, and a parametric study on the role of parent species of a surrogate mixture in predicting flame extinguishment is performed. Ease of changing chemical kinetics in the UNICORN code is demonstrated through the investigation of effects of additives in JP-8 fuel.

关键词： Chemical Kinetics Mechanism Direct Numerical Simulation Conservation Equations Computational Fluid Dynamics Code solution algorithm Strain Rate National Institute of Standards and Technology Thermal Conductivity Reacting Flow Combustion Process

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Transition prediction for three-dimensional boundary layers in computational fluid dynamics applications

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AIAA JOURNAL 2002年第8期40卷 1536-1541页

作者： Crouch, JD Crouch, IWM Ng, LL Boeing Commercial Airplane Grp Aerodynam Res Seattle WA 98124 USA Boeing Commercial Airplane Grp Acoust & Fluid Mech Seattle WA 98124 USA

A method is presented for estimating the laminar/turbulent transition location in three-dimensional boundary layers for computational fluid dynamics (CFD) applications requiring numerous transition estimates with no user intervention. Given the Reynolds number and the C-P distribution, the location of transition is estimated based on the attachment-line state, the potential for relaminarization, the occurrence of laminar separation, and the growth of instabilities. Transition caused by instability is estimated based on N factors calculated for Tollmien-Schlichting waves and for stationary crossflow instabilities. A neural network is used (in place of solving the Orr-Sommerfeld stability equation) for determining the instability growth rates. The current version of the method assumes incompressible How. The boundary-layer flow and instabilities are calculated based on an infinite-sweep (strip boundary layer) approximation;the instability calculations also employ the parallel-How approximation. Comparisons with traditional stability codes show good N-factor agreement over a practical range of C-P distributions. The method is several hundred times faster than traditional stability calculations, and it is robust enough to function as a simple "subroutine" in CFD codes. The method is biased toward application efficiency and simplicity as balanced against improvements in the detailed physical modeling.

关键词： Three Dimensional Boundary Layer CFD Neural Network Methods Freestream Mach Number CFD Codes Tollmien Schlichting waves Swept Wing Neutral Point Sweep Angle solution algorithm

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ARTIFICIAL DISSIPATION MODELS FOR THE EULER EQUATIONS

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AIAA JOURNAL 1986年第12期24卷 1931-1940页

作者： PULLIAM, TH NASA Ames Research Center Moffett Field California

Various artificial dissipation models that are used with central difference algorithms for the Euler equations are analyzed for their effect on accuracy, stability, and convergence rates. In particular, linear and nonlinear models are investigated using an implicit approximate factorization code (ARC2D) for transonic airfoils. Fully implicit application of the dissipation models is shown to improve robustness and convergence rates. The treatment of dissipation models at boundaries will be examined. It will be shown that accurate, error free solutions with sharp shocks can be obtained using a central difference algorithm coupled with an appropriate nonlinear artificial dissipation model. © 1986 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.

关键词： Rankine Hugoniot Relation Total Variation Diminishing Supersonic Flow Viscosity NACA 0012 Navier Stokes Equations solution algorithm Angle of Attack Numerical algorithms Specific Heat

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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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Combining the advantages of discrete-and continuous-time scheduling models: Part 3. General algorithm

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COMPUTERS & CHEMICAL ENGINEERING 2020年 139卷 106848-106848页

作者： Lee, Hojae Maravelias, Christos T. Univ Wisconsin Dept Chem & Biol Engn 1415 Engn Dr Madison WI 53706 USA

One of the main challenges in applying optimization-based scheduling techniques in process industries stems from the different process characteristics and constraints that need to be taken into account when generating a schedule. For instance, consideration of sequence-dependent changeovers may easily make the resulting optimization model computationally expensive. Accordingly, building upon the recently pro-posed Discrete-Continuous algorithm (Lee and Maravelias, 2018), we propose generalized algorithm that enables accurate and fast solution of difficult instances while efficiently handling a wide range of process characteristics. The algorithm combines modeling versatility with computational tractability while guar-anteeing the feasibility and accuracy of the final solution. Through a case study inspired by a real-world brewing process, we show that our algorithm provides accurate and high quality solutions to industrial-scale instances in reasonable time. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： Chemical production scheduling solution algorithm Mixed-integer programming Process operations

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GRID GENERATION FOR 3-DIMENSIONAL TURBOMACHINERY GEOMETRIES INCLUDING TIP CLEARANCE

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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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