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作者： Perrell, Eric R. Power, Greg D. Robinson, Chris Aerospace Engineering Embry-Riddle Aeronautical University 600 South Clyde Morris Blvd. Daytona Beach FL 32114 United States Computational Modeling and Simulation Arnold Engineering Development Center MS 9013 Arnold AFB TN 37388-9013 United States

ISBN: (纸本)9781600867392

A set of computational tools for coupling CFD with solid conduction and convection heat transfer is developed. A modular approach is used in order that the tools can be used in a variety of combinations or in stand-alone applications. The key element to this approach is a library of Surface Data Interchange (SDI) routines callable by any of the computational modules. The routines pass heat-transfer and temperature data, which become updated boundary conditions for the modules. The capability is demonstrated on, and results compared with data from, two experiments. The computational modules used are the Wind-US CFD code, the HTX solid heat conduction module, and the HT1D heat conduction module with empirical coolant convection. One case also introduces a new mesh interpolation tool for noncontiguous surface meshes. Copyright © 2010 by the authors.

关键词： Heat conduction

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Applying data mining methods to blast-related mild traumatic brain injury

Applying data mining methods to blast-related mild traumatic...

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Annual ORNL Biomedical Science & engineering Conference (BSEC)

作者： Jillian S. Gauld Barbara G. Beckerman Oak Ridge National Laboratory Queen's University Kingston Canada Biomedical Engineering and Biomedical Informatics in the Modeling and Simulation Group Computational Sciences and Engineering Division at Oak Ridge National Laboratory Biomedical Science and Engineering Center

ISBN: (纸本)9781424467136;9781424467143

Mild traumatic brain injury (mTBI), or concussion, is one of the most common forms of injury sustained throughout Operations Iraqi Freedom and Enduring Freedom. Diagnosis is difficult for many of the symptoms are very common and may not manifest themselves immediately after the injury. Many studies on blast-related mTBI have been published from research regarding the current war in Iraq and Afghanistan. Continuous work is underway to more accurately determine its causes and symptoms, as mTBI is considered difficult to diagnose. Using the Oak Ridge National Laboratory (ORNL) developed data mining software Piranha, an integrative literature analysis was conducted to assist and facilitate possible research on the processes of mTBI. Data were collected from academic databases as well as Piranha's internet search function. The Piranha categories feature was employed to visualize the areas of overlapping research regarding manifestations of mTBI relating to the biological processes and behavioral changes. Piranha was also used to review current research on mTBI, including animal testing on mice and swine. The integrated results from these data mining analyses revealed areas that could be studied further, as well as a clearer indication of the specific processes of mTBI. This research provides a fresh perspective on one of the war's most common and yet least understood injuries.

关键词： Data mining Brain injuries Laboratories Spatial databases Visual databases Internet Data visualization Biological processes Animals Testing

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Application of the p-multigrid algorithm to discontinuous galerkin formulations of the compressible euler equation

Application of the p-multigrid algorithm to discontinuous ga...

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18th AIAA computational Fluid Dynamics Conference

作者： Mascarenhas, Brendan S. Helenbrook, Brian T. Atkins, Harold L. Clarkson University Potsdam NY 13699-5725 United States NASA Langley Research Center MS 128 Hampton VA 23681-2199 United States Mechanical and Aeronautical Engineering Department United States AIAA United States Computational Modeling and Simulation Branch United States

ISBN: (纸本)1563478994

p-multigrid is an iterative algorithm used to obtain solutions to hp-finite element discretizations. In this work, we have investigated the use of p-multigrid (for p = 2 approximations) and agglomeration multigrid (for p = 0 approximations) to obtain the solution to the discontinuous Galerkin formulation of the compressible Euler equations applied to a model problem. Various diagonal, line solve and sweeping relaxation schemes have been investigated to compare their performance. The model problem analyzed is a 2-D free-steam subsonic flow which is periodic in one direction. For this problem, we have used a structured rectangular mesh and linear analysis is used to obtain the convergence rates (damping factors) of the different schemes. For all orders of p, the damping factors are observed to vary significantly with the angle of the flow with respect to the mesh. The block line relaxation schemes including the alternate direction line (ADL) scheme, with an under-relaxation factor of 2/3, showed the least variation with flow angle. Even when the flow is perfectly aligned with the mesh, these schemes converge well unlike the diagonal relaxation schemes. We also studied the variation of the damping factors with grid refinement and here again the line relaxation schemes showed grid independence at all flow angles, whereas the diagonal schemes were only grid independent at flow angles away from 0° and 180°. For the p = 0 approximations, the block line solve scheme with symmetric Gauss-Seidel (SGS) sweeps and two-level agglomeration multigrid, performs the best, giving damping factors in the range of 0.35 to 0.8 for a wide range of flow angles. The ADL multigrid scheme with Gauss-Seidel sweep also performs very well when the GS sweep is in the direction of the x-component of the flow velocity, giving damping factors between 0.33 and 0.42 for all flow angles less than 90°. For the p = 2 approximations, the ADL relaxation coupled with a two level p-multigrid algorithm (p coa

关键词： Euler equations

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IMPLEMENTATION OF MIXED METHODS AS FINITE DIFFERENCE METHODS AND APPLICATIONS TO NONISOTHERMAL MULTIPHASE FLOW IN POROUS MEDIA

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Journal of computational Mathematics 2006年第3期24卷 281-294页

作者： Zhang-xin Chen Xi-jun Yu Center for Scientific Computation Box 750156 Southern Methodist University Dallas TX 75275-0156 USA Research Center for Science Xi'an Jiaotong University Xi'an 710049 China Center for Advanced Reservoir Modeling and Simulation College Vof Engineering'PekingI University China Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing 100088 China

In this paper we consider mixed finite element methods for second order elliptic problems. In the case of the lowest order Brezzi-Douglas-Marini elements （if d = 2） or Brezzi- Douglas-Duran-Fortin elements （if d = 3） on rectangular parallelepipeds, we show that the mixed method system, by incorporating certain quadrature rules, can be written as a simple, cell-centered finite difference method. This leads to the solution of a sparse, positive semidefinite linear system for the scalar unknown. For a diagonal tensor coefficient, the sparsity pattern for the scalar unknown is a five point stencil if d = 2, and seven if d = 3. For a general tensor coefficient, it is a nine point stencil, and nineteen, respectively. Applications of the mixed method implementation as finite differences to nonisothermal multiphase, multicomponent flow in porous media are presented.

关键词： Finite difference Implementation Mixed method Error estimates Superconvergence Tensor coefficient Nonisothermal multiphase Multicomponent flow Porousmedia.

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Progress towards multi-block large eddy simulations for wind turbine aeroacoustics

Progress towards multi-block large eddy simulations for wind...

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43rd AIAA Aerospace Sciences Meeting and Exhibit

作者： Uzun, Ali Yousuff Hussaini, M. Streett, Craig L. School of Computational Science and Information Technology Florida State University Tallahassee FL 32306-4120 NASA Langley Research Center Hampton VA 23681 AIAA Mathematics and Computational Science and Engineering Computational Modeling and Simulation Branch

This paper reports on the recent progress towards a multi-block Large Eddy simulation (LES) code with OVERSET grid capability that is under development for studying various components of wind turbine noise. Two of the most important components of wind turbine noise are believed to be tip noise and trailing edge noise. The present LES code is therefore being customized towards the study of these two noise components. The LES code employs state-of-the-art compact finite differencing, implicit spatial filtering and non-reflecting boundary conditions. High-order accurate interpolation is also used so as to transfer information among the individual component grids that make up the OVERSET grid topology. The multi-block nature and the OVERSET grid capability of the code allow high-order accurate numerical solutions around wind turbine blade geometries. Preliminary results for the flow over a flat plate with a blunt trailing edge and the tip vortex problem on a generic stationary wing geometry with a rounded tip are presented to illustrate possible applications of the computational methodology.

关键词： Acoustic noise

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Towards tip vortex noise prediction by high-order les on overset grids

Towards tip vortex noise prediction by high-order les on ove...

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Collection of Technical Papers - 11th AIAA/CEAS Aeroacoustics Conference

作者： Uzun, Ali Yousuff Hussaini, M. Streett, Craig L. School of Computational Science Florida State University Tallahassee FL 32306-4120 United States NASA Langley Research Center Hampton VA 23681 United States AIAA United States Mathematics and Computational Science and Engineering Computational Modeling and Simulation Branch United States

ISBN: (纸本)1563477300

This paper reports on a multi-block large eddy simulation (LES) code with overset grid capability which has been developed to primarily study the tip vortex noise problem arising on rotating wind turbine blades. The LES code can also be used to simulate the tip vortices around stationary wing geometries typically found in aeronautical applications. It employs state-of-the-art compact finite differencing, implicit spatial filtering, and non-reflecting boundary conditions on free boundaries, as well as characteristic-type boundary conditions on solid walls. High-order accurate interpolation is used for the transfer of information among the individual component grids that make up the overset grid topology. The multi-block nature and the overset grid capability of the code allow high-order accurate numerical solutions in complex domains. Results for the tip vortex around a stationary wing with a rounded tip are presented to demonstrate the capability of the code. Comparisons of the numerical results with experimental data are also carried out for the validation of the computational methodology.

关键词： Acoustic noise

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Progress towards multi-block large eddy simulations for wind turbine aeroacoustics

Progress towards multi-block large eddy simulations for wind...

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2005 ASME Wind Energy Symposium at the 43rd AIAA Aerospace Sciences Meeting and Exhibit

作者： Uzun, Ali Hussaini, M. Yousuff Streett, Craig L. School of Computational Science and Information Technology Florida State University Tallahassee FL 32306-4120 United States NASA Langley Research Center Hampton VA 23681 United States AIAA United States Depatment of Mathematics and Computational Science and Engineering Computational Modeling and Simulation Branch United States

ISBN: (纸本)1563477262

关键词： Wind turbines

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Complex landing gear noise prediction using a simple toolkit

Complex landing gear noise prediction using a simple toolkit

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43rd AIAA Aerospace Sciences Meeting and Exhibit

作者： Lopes, Leonard V. Brentner, Kenneth S. Morris, Philip J. Lilley, Geoffery M. Lockard, David P. Department of Aerospace Engineering Pennsylvania State University University Park PA United States Computational Modeling and Simulation Branch NASA Langley Research Center Hampton VA United States AIAA United States Department of Aerospace Engineering United States University of Southampton United Kingdom NASA Langley United States

This paper describes the initial development of a method for the prediction of the noise radiated by aircraft landing gear. Called the Landing Gear Model and Acoustic Prediction (LGMAP), it will eventually include all the geometric complexity of a realistic landing gear. This will be achieved by dividing the gear into a number of elements or objects. The noise from each of these elements is described by a simple acoustic model. Each object has three attributes;its geometry and location, and an upstream and downstream environment. This enables the flow or noise from one element to interact with any other. The method is designed to allow improved element acoustic models to be introduced as they become available. This paper contains some initial examples for two objects;a cylinder element and a wheel model. The landing gear is divided into assemblies made up of these elements. The radiated noise is calculated in the time-domain using a source-time-dominant solution to the Ffowcs Williams-Hawkings equation. This initial, rather crude, model is calibrated by comparison with experiment and existing noise prediction methods. The purpose of this paper is primarily to introduce the modeling philosophy rather than make extensive predictions. Though more than one example is given. The model is still in its early development stages and many important acoustic mechanisms are not included. Some of the future plans and necessary extensions to the model are discussed. Copyright © 2005 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Landing gear (aircraft)

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An isolated circular synthetic jet in cross-flow at low momentum-flux ratio

An isolated circular synthetic jet in cross-flow at low mome...

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43rd AIAA Aerospace Sciences Meeting and Exhibit

作者： Milanovic, Ivana M. Zaman, Khairul B. M. Q. Rumsey, Christopher L. University of Hartford West Hartford CT 06117 NASA Glenn Research Center Cleveland OH 44135 NASA Langley Research Center Hampton VA 23681 Department of Mechanical Engineering 200 Bloomfield Av. AIAA Propulsion Systems Division Nozzle Branch Mail Stop 86-7 Computational Modeling and Simulation Branch Mail Stop 128

A joint experimental and computational investigation was carried out for a round synthetic jet issuing normal to a turbulent boundary layer at a momentum-flux ratio of one. Distributions of velocity and turbulence intensity were measured by hot-wire anemometry. Numerical results were obtained using unsteady Reynolds-averaged Navier-Stokes (URANS) computations. Time and phase-averaged flow properties were compared on the cross sectional plane at x/ D = 0.53, 5 and 10 as well as on the axial plane of symmetry. Overall, the numerical results agreed well with the experimental data. CFD predicted a somewhat larger velocity deficit in regions of low-momentum fluid pulled up from the boundary layer. Phase-averaged velocity contours at the plane of symmetry indicated good match between experiments and CFD regarding the size and the position of the periodic flow structure. However, some differences occurred in details such as the shape and inclination of the low-speed flow structure.

关键词： Jets

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Design and evaluation of modifications to the NASA Langley flow impedance tube

Design and evaluation of modifications to the NASA Langley f...

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Collection of Technical Papers - 10th AIAA/CEAS Aeroacoustics Conference

作者： Jones, M.G. Watson, W.R. Parrott, T.L. Smith, C.D. NASA Langley Research Center Hampton VA 23681-2199 United States Lockheed Martin Engineering and Sciences Hampton VA 23681-2199 United States Structural Acoustics Branch Mail Stop 463 Computational Modeling and Simulation Branch Mail Stop 128 Mail Stop 105

ISBN: (纸本)1563477130

The need to minimize fan noise radiation from commercial aircraft engine nacelles continues to provide an impetus for developing new acoustic liner concepts. If the full value of such concepts is to be attained, an understanding of grazing flow effects is crucial. Because of this need for improved understanding of grazing flow effects, the NASA Langley Research Center Liner Physics Group has invested a large effort over the past decade into the development of a 2-D finite element method that characterizes wave propagation through a lined duct. The original test section in the Langley Grazing Incidence Tube was used to acquire data needed for implementation of this finite element method. This test section employed a stepper motor-driven axial-traversing bar, embedded in the wall opposite the test liner, to position a flush-mounted microphone at pre-selected locations. Complex acoustic pressure data acquired with this traversing microphone were used to educe the acoustic impedance of test liners using this 2-D finite element method and a local optimization technique. Results acquired in this facility have been extensively reported, and were compared with corresponding results from various U.S. aeroacoustics laboratories in the late 1990's. Impedance data comparisons acquired from this multi-laboratory study suggested that it would be valuable to incorporate more realistic 3-D aeroacoustic effects into the impedance eduction methodology. This paper provides a description of modifications that have been implemented to facilitate studies of 3-D effects. The two key features of the modified test section are (1) the replacement of the traversing bar and its flush-mounted microphone with an array of 95 fixed-location microphones that are flush-mounted in all four walls of the duct, and (2) the inclusion of a suction device to modify the boundary layer upstream of the lined portion of the duct. The initial results achieved with the modified test section are provided in this

关键词： Acoustic impedance

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