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- Adaptive Numerical Dissipation/Filer Controls (1)
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Articles 1 - 7 of 7
Full-Text Articles in Physical Sciences and Mathematics
Entropy Splitting For High Order Numerical Simulation Of Vortex Sound At Low Mach Numbers, Bernhard Müller, H. C. Yee
Entropy Splitting For High Order Numerical Simulation Of Vortex Sound At Low Mach Numbers, Bernhard Müller, H. C. Yee
United States National Aeronautics and Space Administration: Publications
Several recent developments in efficient, stable, highly parallelizable high order non-dissipative spatial schemes with characteristic based filters that exhibit low dissipation for long time linear and nonlinear wave propagations are utilized for computational aeroacoustics (CAA). For stability consideration, the Euler equations are split into a conservative and a symmetric non-conservative portion. Due to the large disparity of acoustic and stagnation quantities in low Mach number aeroacoustics, the split Euler equations are formulated in perturbation form to minimize numerical cancellation errors. Spurious oscillations are suppressed by a characteristic-based filter. The method has been applied to accurately simulate the sound emitted by …
Responses Of An Arctic Landscape To Lateglacial And Early Holocene Climatic Changes: The Importance Of Moisture, Daniel H. Mann, Dorothy M. Peteet, Richard E. Reanier, Michael L. Kunz
Responses Of An Arctic Landscape To Lateglacial And Early Holocene Climatic Changes: The Importance Of Moisture, Daniel H. Mann, Dorothy M. Peteet, Richard E. Reanier, Michael L. Kunz
United States National Aeronautics and Space Administration: Publications
Many of the physical and biological processes that characterize arctic ecosystems are unique to high latitudes, and their sensitivities to climate change are poorly understood. Stratigraphic records of land–surface processes and vegetation change in the Arctic Foothills of northern Alaska reveal how tundra landscapes responded to climatic changes between 13,000 and 8000 14Cyr BP. Peat deposition began and shrub vegetation became widespread ca. 12,500 14Cyr BP, probably in response to the advent of warmer and wetter climate. Increased slope erosion caused rapid alluviation in valleys, and Populus trees spread northward along braided floodplains before 11,000 14Cyr BP. …
Radiometric Cross-Calibration Of The Landsat-7 Etm+ And Landsat-5 Tm Sensors Based On Tandem Data Sets, P.M. Teillet, J. L. Barker, B. L. Markham, R. R. Irish, G. Fedosejevs, J.C. Storey
Radiometric Cross-Calibration Of The Landsat-7 Etm+ And Landsat-5 Tm Sensors Based On Tandem Data Sets, P.M. Teillet, J. L. Barker, B. L. Markham, R. R. Irish, G. Fedosejevs, J.C. Storey
United States National Aeronautics and Space Administration: Publications
Early in its mission, the Landsat-7 spacecraft was temporarily placed in a ‘‘tandem’’ orbit very close to that of the Landsat-5 spacecraft in order to facilitate the establishment of sensor calibration continuity between the Landsat-7 Enhanced Thematic Mapper Plus (ETM+) and Landsat-5 Thematic Mapper (TM) sensors. The key period for the tandem configuration was June 1–4, 1999, during which hundreds of nearly coincident matching scenes were recorded by both the Landsat-7 ETM+ and, in cooperation with Space Imaging/EOSAT and international ground stations, the Landsat-5 TM as well. The paper presents a methodology for radiometric cross-calibration of the solar reflective spectral …
Building Blocks For Reliable Complex Nonlinear Numerical Simulations, Helen Yee
Building Blocks For Reliable Complex Nonlinear Numerical Simulations, Helen Yee
United States National Aeronautics and Space Administration: Publications
This chapter describes some of the building blocks to ensure a higher level of confidence in the predictability and reliability (PAR) of numerical simulation of multiscale complex nonlinear problems. The focus is on relating PAR of numerical simulations with complex nonlinear phenomena of numerics. To isolate sources of numerical uncertainties, the possible discrepancy between the chosen partial differential equation (PDE) model and the real physics and/or experimental data is set aside. The discussion is restricted to how well numerical schemes can mimic the solution behavior of the underlying PDE model for finite time steps and grid spacings. The situation is …
Designing Adaptive Low-Dissipative High Order Schemes For Long-Time Integrations, Helen Yee, Bjorn Sjögreen
Designing Adaptive Low-Dissipative High Order Schemes For Long-Time Integrations, Helen Yee, Bjorn Sjögreen
United States National Aeronautics and Space Administration: Publications
A general framework for the design of adaptive low-dissipative high order schemes is presented. It encompasses a rather complete treatment of the numerical approach based on four integrated design criteria: (1) For stability considerations, condition the governing equations before the application of the appropriate numerical scheme whenever it is possible. (2) For consistency, compatible schemes that possess stability properties, including physical and numerical boundary condition treatments, similar to those of the discrete analogue of the continuum are preferred. (3) For the minimization of numerical dissipation contamination, efficient and adaptive numerical dissipation control to further improve nonlinear stability and accuracy should …
Climate Change And Extreme Weather Events - Implications For Food Production, Plant Diseases, And Pests, Cynthia Rosenzweig, Ana Iglesius, X. B. Yang, Paul R. Epstein, Eric Chivian
Climate Change And Extreme Weather Events - Implications For Food Production, Plant Diseases, And Pests, Cynthia Rosenzweig, Ana Iglesius, X. B. Yang, Paul R. Epstein, Eric Chivian
United States National Aeronautics and Space Administration: Publications
Current and future energy use from burning of fossil fuels and clearing of forests for cultivation can have profound effects on the global environment, agriculture, and the availability of low-cost, high-quality food for humans. Individual farmers and consumers are expected to be affected by changes in global and regional climate. The agricultural sector in both developing and developed areas needs to understand what is at stake and to prepare for the potential for change wisely.
Despite tremendous improvements in technology and crop yield potential, food production remains highly dependent on climate, because solar radiation, temperature, and precipitation are the main …
Entropy Splitting For High Order Numerical Simulation Of Vortex Sound At Low Mach Numbers, B. Müller, H.C. Yee
Entropy Splitting For High Order Numerical Simulation Of Vortex Sound At Low Mach Numbers, B. Müller, H.C. Yee
United States National Aeronautics and Space Administration: Publications
A method of minimizing numerical errors, and improving nonlinear stability and accuracy associated with low Mach number computational aeroacoustics (CAA) is proposed. The method consists of two levels.