Institution
Langley Research Center
Facility•Hampton, Virginia, United States•
About: Langley Research Center is a facility organization based out in Hampton, Virginia, United States. It is known for research contribution in the topics: Mach number & Wind tunnel. The organization has 15945 authors who have published 37602 publications receiving 821623 citations. The organization is also known as: NASA Langley & NASA Langley Research Center.
Topics: Mach number, Wind tunnel, Aerodynamics, Boundary layer, Supersonic speed
Papers published on a yearly basis
Papers
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TL;DR: In this paper, a finite difference for elastic waves is introduced and the model is based on the first order system of equations for the velocities and stresses of the elastic wave and is tested on a series of examples including the Lamb problem, scattering from plane interf aces and scattering from a fluid-elastic interface.
Abstract: A finite difference for elastic waves is introduced. The model is based on the first order system of equations for the velocities and stresses. The differencing is fourth order accurate on the spatial derivatives and second order accurate in time. The model is tested on a series of examples including the Lamb problem, scattering from plane interf aces and scattering from a fluid-elastic interface. The scheme is shown to be effective for these problems. The accuracy and stability is insensitive to the Poisson ratio. For the class of problems considered here it is found that the fourth order scheme requires for two-thirds to one-half the resolution of a typical second order scheme to give comparable accuracy.
182 citations
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Free University of Berlin1, Goddard Space Flight Center2, Universities Space Research Association3, National Oceanic and Atmospheric Administration4, University of Toronto5, York University6, National Center for Atmospheric Research7, University of California, Los Angeles8, University of Reading9, Max Planck Society10, Goddard Institute for Space Studies11, Met Office12, Science Applications International Corporation13, Langley Research Center14, European Centre for Medium-Range Weather Forecasts15, AES Corporation16
TL;DR: In this article, the authors present an assessment of the performance of the middle atmosphere climate models, and preliminary results from this evaluation are presented here, showing that although all 13 models represent most major features of the mean atmospheric state, there are deficiencies in the magnitude and location of the features, which cannot easily be traced to the formulation (resolution or the parameterizations included) of the models.
Abstract: To investigate the effects of the middle atmosphere on climate, the World Climate Research Programme is supporting the project "Stratospheric Processes and their Role in Climate" (SPARC). A central theme of SPARC, to examine model simulations of the coupled troposphere—middle atmosphere system, is being performed through the initiative called GRIPS (GCM—Reality Intercomparison Project for SPARC). In this paper, an overview of the objectives of GRIPS is given. Initial activities include an assessment of the performance of middle atmosphere climate models, and preliminary results from this evaluation are presented here. It is shown that although all 13 models evaluated represent most major features of the mean atmospheric state, there are deficiencies in the magnitude and location of the features, which cannot easily be traced to the formulation (resolution or the parameterizations included) of the models. Most models show a cold bias in all locations, apart from the tropical tropopause region wher...
182 citations
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01 Jan 2002TL;DR: The numerical results presented indicate that the particle swarm optimization algorithm is able to reliably find the optimum design for the problem presented here and recommendations as to the utility of the algorithm in future multidisciplinary optimization applications are made.
Abstract: The purpose of this paper is to demonstrate the application of particle swarm optimization to a realistic multidisciplinary optimization test problem. The paper's new contributions to multidisciplinary optimization is the application of a new algorithm for dealing with the unique challenges associated with multidisciplinary optimization problems, and recommendations as to the utility of the algorithm in future multidisciplinary optimization applications. The selected example is a bi-level optimization problem that demonstrates severe numerical noise and has a combination of continuous and truly discrete design variables. The use of traditional gradient-based optimization algorithms is thus not practical. The numerical results presented indicate that the particle swarm optimization algorithm is able to reliably find the optimum design for the problem presented here. The algorithm is capable of dealing with the unique challenges posed by multidisciplinary optimization as well as the numerical noise and truly discrete variables present in the current example problem.
182 citations
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University of Colorado Boulder1, NASA Headquarters2, University of New Hampshire3, Langley Research Center4, Harvard University5, Ames Research Center6, City College of New York7, University of Utah8, National Center for Atmospheric Research9, Earth System Research Laboratory10, United States Naval Research Laboratory11, Goddard Space Flight Center12, University of Montana13
TL;DR: The studies of emissions and atmospheric composition, clouds and climate coupling by regional surveys (SEAC4RS) field mission as mentioned in this paper employed the most comprehensive airborne payload to date to investigate atmospheric composition over North America.
Abstract: The Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) field mission based at Ellington Field, Texas, during August and September 2013 employed the most comprehensive airborne payload to date to investigate atmospheric composition over North America. The NASA ER-2, DC-8, and SPEC Inc. Learjet flew 57 science flights from the surface to 20 km. The ER-2 employed seven remote sensing instruments as a satellite surrogate and eight in situ instruments. The DC-8 employed 23 in situ and five remote sensing instruments for radiation, chemistry, and microphysics. The Learjet used 11 instruments to explore cloud microphysics. SEAC4RS launched numerous balloons, augmented Aerosol RObotic NETwork, and collaborated with many existing ground measurement sites. Flights investigating convection included close coordination of all three aircraft. Coordinated DC-8 and ER-2 flights investigated the optical properties of aerosols, the influence of aerosols on clouds, and the performance of new instruments for satellite measurements of clouds and aerosols. ER-2 sorties sampled stratospheric injections of water vapor and other chemicals by local and distant convection. DC-8 flights studied seasonally evolving chemistry in the Southeastern U.S., atmospheric chemistry with lower emissions of NOx and SO2 than in previous decades, isoprene chemistry under high and low NOx conditions at different locations, organic aerosols, air pollution near Houston and in petroleum fields, smoke from wildfires in western forests and from agricultural fires in the Mississippi Valley, and the ways in which the chemistry in the boundary layer and the upper troposphere were influenced by vertical transport in convective clouds.
182 citations
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TL;DR: In this article, large-scale structures in a plane turbulent mixing layer are studied through the use of the proper orthogonal decomposition (POD) and extensive experimental measurements are obtained in a turbulent plane mixing layer by means of two cross-wire rakes aligned normal to the direction of the mean shear and perpendicular to the mean flow direction.
Abstract: Large-scale structures in a plane turbulent mixing layer are studied through the use of the proper orthogonal decomposition (POD). Extensive experimental measurements are obtained in a turbulent plane mixing layer by means of two cross-wire rakes aligned normal to the direction of the mean shear and perpendicular to the mean flow direction. The measurements are acquired well into the asymptotic region. From the measured velocities the two-point spectral tensor is calculated as a function of separation in the cross-stream direction and spanwise and streamwise wavenumbers. The continuity equation is then used for the calculation of the non-measured components of the tensor. The POD is applied using the cross-spectral tensor as its kernel. This decomposition yields an optimal basis set in the mean square sense. The energy contained in the POD modes converges rapidly with the first mode being dominant (49% of the turbulent kinetic energy). Examination of these modes shows that the first mode contains evidence of both known flow organizations in the mixing layer, i.e. quasi-two-dimensional spanwise structures and streamwise aligned vortices. Using the shot-noise theory the dominant mode of the POD is transformed back into physical space. This structure is also indicative of the known flow organizations.
181 citations
Authors
Showing all 16015 results
Name | H-index | Papers | Citations |
---|---|---|---|
Daniel J. Jacob | 162 | 656 | 76530 |
Donald R. Blake | 118 | 727 | 49697 |
Veerabhadran Ramanathan | 100 | 301 | 47561 |
Raja Parasuraman | 91 | 402 | 41455 |
Robert W. Platt | 88 | 638 | 31918 |
James M. Russell | 87 | 691 | 29383 |
Daniel J. Inman | 83 | 918 | 37920 |
Antony Jameson | 79 | 474 | 31518 |
Ya-Ping Sun | 79 | 277 | 28722 |
Patrick M. Crill | 79 | 228 | 20850 |
Richard B. Miles | 78 | 759 | 25239 |
Patrick Minnis | 77 | 490 | 23403 |
Robert W. Talbot | 77 | 297 | 19783 |
Raphael T. Haftka | 76 | 773 | 28111 |
Jack E. Dibb | 75 | 344 | 18399 |