Physical Sciences and Mathematics Commons^™

On Skew-Symmetric Splitting And Entropy Conservation Schemes For The Euler Equations, Björn Sjögreen, H.C. Yee

United States National Aeronautics and Space Administration: Publications

The Tadmor type of entropy conservation formulation for the Euler equations and various skew-symmetric splittings of the inviscid flux derivatives are discussed. Numerical stability of high order central and Padé type (centered compact) spatial discretization is enhanced through the application of these formulations. Numerical test on a 2-D vortex convection problem indicates that the stability and accuracy of these formulations using the same high order central spatial discretization are similar for vortex travel up to a few periods. For two to three times longer time integrations, their corresponding stability and accuracy behaviors are very different. The goal of this work …

Comparative Study Of High Order Methods For Subsonic Turbulence Simulation With Stochastic Forcing, Alexei G. Kritsuk, H. C. Yee, Björn Sjögreen, Dmitry Kotov

United States National Aeronautics and Space Administration: Publications

A class of spatially seventh-order nonlinear filter methods with adaptive dissipation control developed by Yee & Sjögreen [1, 2] is tested on three-dimensional subsonic turbulence simulations with stochastic forcing. The Euler equations are solved using the Strang operator splitting of the homogeneous part of the equations and the stochastic forcing term, with an ODE solver used to integrate the latter. Both Ducros et al. and Kennedy-Gruber skew-symmetric split formulations of the inviscid flux derivatives are considered to minimize the use of numerical dissipation. The nonlinear filter methods are shown to be numerically stable for this application at least up to …

On Entropy Conservation And Kinetic Energy Preservation Methods, H. C. Yee, Björn Sjögreen

United States National Aeronautics and Space Administration: Publications

The Tadmor-type entropy conservative method using the mathematical logarithmic entropy function and two forms of the Sjögreen & Yee entropy conservative methods using the Harten entropy function are examined for their nonlinear stability and accuracy in very long time integration of the Euler equations of compressible gas dynamics. Following the same procedure as Ranocha [6] these entropy conservative methods can be made kinetic energy preserving with minimum added computational effort. The focus of this work is to examine the nonlinear stability and accuracy of these newly introduced high order entropy conserving and kinetic energy preserving methods for very long time …

High-Order Finite-Difference Nonlinear Filter Methods For Subsonic Turbulence Simulation With Stochastic Forcing, Alexei G. Kritsuk, Dmitry Kotov, Bjorn Sjögreen, Helen C. Yee

United States National Aeronautics and Space Administration: Publications

Numerical stability of high-order fi lter schemes developed by Yee & Sjogreen is tested on thr~dimensional turbulence simulations with stochastic forcing and their performance is compared with that ofTVD and \VENO schemes. The bestperforming filter method employs an eighth-order central base scheme with the Kennedy & Gruber skew-symmetric splitting of the inviscid fttLx derivative, a wavelet-based local flow sensor, a nonlinear filter utilizing the dissipative portion of seventh-order \\'ENO scheme, and an explicit third- or fourth-order RungeKutta t ime integration. \Ve show that the filter scheme is more computational]y efficient and provides a wider spectral bandwidth compared to the seventh-order …

Skew-Symmetric Splitting Of High-Order Central Schemes With Nonlinear Filters For Computational Aeroacoustics Turbulence With Shocks, Bjorn Sjögreen, Helen C. Yee, Alan A. Wray

United States National Aeronautics and Space Administration: Publications

A class of high-order nonlinear filter schemes by Yee et al. (J Comput Phys 150:199–238, 1999), Sjögreen and Yee (J Comput Phys 225:910–934, 2007), and Kotov et al. (Commun Comput Phys 19:273–300, 2016; J Comput Phys 307:189–202, 2016) is examined for long-time integrations of computational aeroacoustics (CAA) turbulence applications. This class of schemes was designed for an improved nonlinear stability and accuracy for long-time integration of compressible direct numerical simulation and large eddy simulation computations for both shock-free turbulence and turbulence with shocks. They are based on the skew-symmetric splitting version of the high-order central base scheme in conjunction with …

High Order Entropy Conservative Central Schemes For Wide Ranges Of Compressible Gas Dynamics And Mhd Flows, Björn Sjögreen, H.C. Yee

United States National Aeronautics and Space Administration: Publications

The Sjogreen and Yee [31]high order entropy conservative numerical method for compressible gas dynamics is extended to include discontinuities and also extended to equations of ideal magnetohydrodynamics (MHD). The basic idea is based on Tadmor’s [40]original work for inviscid perfect gas flows. For the MHD four formulations of the MHD are considered: (a) the conservative MHD, (b) the Godunov [14]non-conservative form, (c) the Janhunen [19]– MHD with magnetic field source terms, and (d) a MHD with source terms by Brackbill and Barnes[5]. Three forms of the high order entropy numerical fluxes for the MHD in the finite difference framework are …

Groundwater Withdrawals Under Drought: Reconciling Grace And Land Surface Models In The United States High Plains Aquifer, Wanshu Nie, Benjamin Zaitchik, Matthew Rodell, Sujay V. Kumar, Martha C. Anderson, Christopher Hain

United States National Aeronautics and Space Administration: Publications

Advanced Land Surface Models (LSM) offer a powerful tool for studying hydrological variability. Highly managed systems, however, present a challenge for these models, which typically have simplified or incomplete representations of human water use. Here we examine recent groundwater declines in the US High Plains Aquifer (HPA), a region that is heavily utilized for irrigation and that is also affected by episodic drought. To understand observed decline in groundwater and terrestrial water storage during a recent multiyear drought, we modify the Noah-MP LSM to include a groundwater irrigation scheme. To account for seasonal and interannual variability in active irrigated area, …

Two Decades Old Entropy Stable Method For The Euler Equations Revisited, Björn Sjögreen, H. C. Yee

United States National Aeronautics and Space Administration: Publications

The two decades old high order central differencing via entropy splitting and summation-by-parts (SBP) difference closure of Olsson and Oliger, Gerritsen and Olsson, and Yee et al. [2, 7, 25] is revisited. The entropy splitting is a form of skewsymmetric splitting in terms of the physical entropy of the nonlinear Euler flux derivatives. Central differencing applied to the entropy splitting form of the Euler flux derivatives together with SBP difference operators will, hereafter, be referred to as entropy split schemes.

Corrigendum To “On High Order Finite-Difference Metric Discretizations Satisfying Gcl On Moving And Deforming Grids” [J. Comput.Phys. 265 (2014) 211–220], Björn Sjögreen, H.C. Yee, Marcel Vinokur

United States National Aeronautics and Space Administration: Publications

The authors regret that the already published version contains some typographic errors in the formulas for the Runge-Kutta moving metric time stepping method.

Joint Hierarchical Models For Sparsely Sampled High-Dimensional Lidar And Forest Variables, Andrew O. Finley, Sudipto Banerjee, Yuzhen Zhou, Bruce D. Cook, Chad Babcock

United States National Aeronautics and Space Administration: Publications

Recent advancements in remote sensing technology, specifically Light Detection and Ranging (LiDAR) sensors, provide the data needed to quantify forest characteristics at a fine spatial resolution over large geographic domains. From an inferential standpoint, there is interest in prediction and interpolation of the often sparsely sampled and spatially misaligned LiDAR signals and forest variables. We propose a fully process-based Bayesian hierarchical model for above ground biomass (AGB) and LiDAR signals. The processbased framework offers richness in inferential capabilities, e.g., inference on the entire underlying processes instead of estimates only at pre-specified points. Key challenges we obviate include misalignment between the …

Spurious Behavior Of Shock-Capturing Methods By The Fractional Step Approach: Problems Containing Stiff Source Terms And Discontinuities, H.C. Yee, D.V. Kotov, Wei Wang, Chi-Wang Shu

United States National Aeronautics and Space Administration: Publications

The goal of this paper is to relate numerical dissipations that are inherited in high order shock-capturing schemes with the onset of wrong propagation speed of discontinuities. For pointwise evaluation of the source term, previous studies indicated that the phenomenon of wrong propagation speed of discontinuities is connected with the smearing of the discontinuity caused by the discretization of the advection term. The present study focuses only on solving the reactive system by the fractional step method using the Strang splitting. Studies shows that the degree of wrong propagation speed of discontinuities is highly dependent on the accuracy of the …

Comparative Study Of High-Order Positivity-Preserving Weno Schemes, D. V. Kotov, Helen C. Yee, Bjorn Sjögreen

United States National Aeronautics and Space Administration: Publications

In gas dynamics and magnetohydrodynamics flows, physically, the density ρ and the pressure p should both be positive. In a standard conservative numerical scheme, however, the computed internal energy is obtained by subtracting the kinetic energy from the total energy, resulting in a computed p that may be negative. Examples are problems in which the dominant energy is kinetic. Negative ρ may often emerge in computing blast waves. In such situations the computed eigenvalues of the Jacobian will become imaginary. Consequently, the initial value problem for the linearized system will be ill posed. This explains why failure of preserving positivity …

Variations Of The Apparent Angular Size Of The Sun Across The Entire Solar System: Implications For Planetary Opposition Surges, Estelle Déau

United States National Aeronautics and Space Administration: Publications

We test several convolution and deconvolution models on phase curves at small phase angles (0.0011° < α < 1.51°) that have the highest phase angle sampling to date.These curves were provided by cameras on board several NASA missions (Clementine/UVVIS, Galileo/SSI and Cassini/ISS) when the Sun had different apparent angular radii (α_☼ = 0.266°, 0.051°, 0.028°). For the smallest phase angles, the brightness of the objects (Moon, Europa and the Saturn’s rings) exhibits a strong round-off below the angular size of the Sun. The brightness continues to increase below α_☼ before finally flattening at 0.4α_☼. These behaviors are consistent with the convolution models tested. A simple deconvolution model is also used and agrees with laboratory measurements at extremely small phase angles that do not show any flattening [Psarev V, Ovcharenko A, Shkuratov YG, …

Large-Eddy/Reynolds-Averaged Navier–Stokes Simulation Of A Supersonic Reacting Wall Jet, Jack R. Edwards, John A. Boles, Robert A. Baurle

United States National Aeronautics and Space Administration: Publications

This work presents results from large-eddy/Reynolds-averaged Navier–Stokes (LES/RANS) simulations of the well-known Burrows–Kurkov supersonic reacting wall-jet experiment. Generally good agreement with experimental mole fraction, stagnation temperature, and Pitot pressure profiles is obtained for non-reactive mixing of the hydrogen jet with a non-vitiated air stream. A lifted flame, stabilized between 15 and 20 cm downstream of the hydrogen jet, is formed for hydrogen injected into a vitiated air stream. Flame stabilization occurs closer to the hydrogen injection location when a three-dimensional combustor geometry (with boundary layer development resolved on all walls) is considered. Volumetric expansion of the reactive shear layer is …

Snow Cover, Snowmelt Timing And Stream Power In The Wind River Range, Wyoming, Dorothy K. Hall, James L. Foster, Nicolo E. Digirolamo, George A. Riggs

United States National Aeronautics and Space Administration: Publications

Earlier onset of springtime weather, including earlier snowmelt, has been documented in the western United States over at least the last 50 years. Because the majority (N70%) of the water supply in the western U.S. comes from snowmelt, analysis of the declining spring snowpack (and shrinking glaciers) has important implications for the management of streamflow. The amount of water in a snowpack influences stream discharge which can also influence erosion and sediment transport by changing stream power, or the rate at which a stream can do work, such as move sediment and erode the stream bed. The focus of this …

The Next Landsat Satellite: The Landsat Data Continuity Mission, James R. Irons, John L. Dwyer, Julia A. Barsi

United States National Aeronautics and Space Administration: Publications

The National Aeronautics and Space Administration (NASA) and the Department of Interior United States Geological Survey (USGS) are developing the successor mission to Landsat 7 that is currently known as the Landsat Data Continuity Mission (LDCM). NASA is responsible for building and launching the LDCM satellite observatory. USGS is building the ground system and will assume responsibility for satellite operations and for collecting, archiving, and distributing data following launch. The observatory will consist of a spacecraft in low-Earth orbit with a two-sensor payload. One sensor, the Operational Land Imager (OLI), will collect image data for nine shortwave spectral bands over …

A Notched Coupon Approach For Tensile Testing Of Braided Composites, Lee W. Kohlman, Justin L. Bail, Gary D. Roberts, Jonathan A. Salem, Richard E. Martin, Wieslaw K. Binienda

United States National Aeronautics and Space Administration: Publications

A notched coupon geometry was evaluated as a method for tensile testing of 2D triaxial braid composites. Edge initiated shear failure has been observed in transverse tension tests using straight-sided coupons based on ASTM D3039. The notched coupon was designed to reduce the effects of edge initiated failure and produce the desired tensile failure. A limited set of tests were performed with partial pressurization of tubes to determine the transverse tensile strength in the absence of edge initiated failure. The transverse strength measured with the notched coupons was considerably higher than the straight-sided coupons, comparable to the tube results, and …

Assimilation Of Grace Terrestrial Water Storage Into A Land Surface Model: Evaluation And Potential Value For Drought Monitoring In Western And Central Europe, Bailing Li, Matthew Rodell, Benjamin F. Zaitchik, Rolf H. Reichle, Randal D. Koster, Tonie M. Van Dam

United States National Aeronautics and Space Administration: Publications

A land surface model’s ability to simulate states (e.g., soil moisture) and fluxes (e.g., runoff) is limited by uncertainties in meteorological forcing and parameter inputs as well as inadequacies in model physics. In this study, anomalies of terrestrial water storage (TWS) observed by the Gravity Recovery and Climate Experiment (GRACE) satellite mission were assimilated into the NASA Catchment land surface model in western and central Europe for a 7-year period, using a previously developed ensemble Kalman smoother. GRACE data assimilation led to improved runoff estimates (in temporal correlation and root mean square error) in 17 out of 18 hydrological basins, …

Benchmark Assessment Of Automated Delamination Propagation Capabilities In Finite Element Codes For Static Loading, Adrian C. Orifici, Ronald Krueger

United States National Aeronautics and Space Administration: Publications

With the increasing implementation in to commercial finite element(FE) codes of capabilities for simulating delamination propagation in composite materials, the need for benchmarking and assessing these capabilities is critical. In this study, the capabilities of the commercial FE code Marc^TM 2008r1 with implementation of the Virtual Crack Closure Technique(VCCT) was assessed. Benchmark delamination propagation results for several specimen configurations were generated using a numerical approach. Specimens were analyzed with three-dimensional and two-dimensional models, and compared with previous analyses using Abaqus^® with the VCCT implemented. The results demonstrated that the VCCT implementation in Marc^TM was capable of accurately …

Polarimetric Retrievals Of Surface And Cirrus Clouds Properties In The Region Affected By The Deepwater Horizon Oil Spill, Matteo Ottaviani, Brian Cairns, Jacek Chowdhary, Bastiaan Van Diedenhoven, Kirk Knobelspiesse, Chris Hostetler, Rich Ferrare, Sharon Burton, John Hair, Michael D. Obland, Raymond Rogers

United States National Aeronautics and Space Administration: Publications

In 2010, the Goddard Institute for Space Studies (GISS) Research Scanning Polarimeter (RSP) performed several aerial surveys over the region affected by the oil spill caused by the explosion of the Deepwater Horizon offshore platform. The instrument was deployed on the NASA Langley B200 aircraft together with the High Spectral Resolution Lidar (HSRL), which provides information on the distribution of the aerosol layers beneath the aircraft, including an accurate estimate of aerosol optical depth.

This work illustrates the merits of polarization measurements in detecting variations of ocean surface properties linked to the presence of an oil slick. In particular, we …

Linearized T-Matrix And Mie Scattering Computations, R. Spurr, J. Wang, J. Zeng, M. I. Mishchenko

United States National Aeronautics and Space Administration: Publications

We present a new linearization of T-Matrix and Mie computations for light scattering by non-spherical and spherical particles, respectively. In addition to the usual extinc- tion and scattering cross-sections and the scattering matrix outputs, the linearized models will generate analytical derivatives of these optical properties with respect to the real and imaginary parts of the particle refractive index, and (for non-spherical scatterers) with respect to the ‘‘shape’’ parameter (the spheroid aspect ratio, cylinder diameter/height ratio, Chebyshev particle deformation factor). These derivatives are based on the essential linearity of Maxwell’s theory. Analytical derivatives are also available for polydisperse particle size distribution …

Response Of Spherical Diffusion Flames Subjected To Rotation: Microgravity Experimentation And Computational Simulation, Sean W. Yoo, Swetaprovo Chaudhuri, Kurt R. Sacksteder, Peng Zhang, Delin Zhu, Chung K. Law

United States National Aeronautics and Space Administration: Publications

Microgravity experiments were conducted in the 2.2-s drop tower and zero-gravity facility at NASA-GRC to gain fundamental understanding of the effects of spinning on an otherwise spherical diffusion flame. The flames were generated by injecting either a fuel or an oxidizer mixture from a porous burner to a controlled ambient of either an oxidizer or fuel mixture, respectively. Results show that the polar flame location scales with the angular velocity monotonically as ω^a, where a is greater and smaller than unity for small and large spinning velocities, respectively. On the contrary, the equatorial flame location responds nonmonotonically to …

Ceramic Thin Film Thermocouples For Sic-Based Ceramic Matrix Composites, John D. Wrbanek, Gustave C. Fralick, Dongming Zhu

United States National Aeronautics and Space Administration: Publications

Conductive ceramic thin film thermocouples were investigated for application to silicon carbide fiber reinforced silicon carbide ceramic matrix composite (SiC/SiC CMC) components. High temperature conductive oxides based on indium and zinc oxides were selected for testing to high temperatures in air. Sample oxide films were first sputtered-deposited on alumina substrates then on SiC/SiC CMC sample disks. Operational issues such as cold junction compensation to a 0 °C reference, resistivity and thermopower variations are discussed. Results show that zinc oxides have an extremely high resistance and thus increased complexity for use as a thermocouple, but thermocouples using indium oxides can achieve …

Forty-Year Calibrated Record Of Earth-Reflected Radiance From Landsat: A Review, Brian L. Markham, Dennis L. Helder

United States National Aeronautics and Space Administration: Publications

Sensors on Landsat satellites have been collecting images of the Earth's surface for nearly 40 years. These images have been invaluable for characterizing and detecting changes in the land cover and land use of the world. Although initially conceived as primarily picture generating sensors, even the early sensors were radiometrically calibrated and spectrally characterized prior to launch and incorporated some capabilities to monitor their radiometric calibration once on orbit. Recently, as the focus of studies has shifted to monitoring Earth surface parameters over significant periods of time, serious attention has been focused toward bringing the data from all these sensors …

Iterative Atmospheric Correction Scheme And The Polarization Color Of Alpine Snow, Matteo Ottaviani, Brian Cairns, Rich Ferrare, Raymond Rogers

United States National Aeronautics and Space Administration: Publications

Characterization of the Earth’s surface is crucial to remote sensing, both to map geomorphological features and because subtracting this signal is essential during retrievals of the atmospheric constituents located between the surface and the sensor. Current operational algorithms model the surface total reflectance through a weighted linear combination of a few geometry-dependent kernels, each devised to describe a particular scattering mechanism. The information content of these measurements is overwhelmed by that of instruments with polarization capabilities: proposed models in this case are based on the Fresnel reflectance of an isotropic distribution of facets. Because of its remarkable lack of spectral …

Optimal Control Modification For Robust Adaptive Control With Large Adaptive Gain, Nhan T. Nguyen

United States National Aeronautics and Space Administration: Publications

In the presence of large uncertainties, a control system needs to be able to adapt rapidly to regain performance. Fast adaptation is referred to the implementation of adaptive control with a large adaptive gain so as to reduce the tracking error rapidly. However, a large adaptive gain can lead to highfrequency oscillations which can adversely affect robustness. A new adaptive law, called optimal control modification, is presented that can achieve robust adaptation with a large adaptive gain without incurring high-frequency oscillations. The modification is based on a minimization of the L₂ norm of the tracking error bounded away from …

Continental-Scale Validation Of Modis-Based And Ledaps Landsat Etm+ Atmospheric Correction Methods, Junchang Ju, David P. Roy, Eric Vermote, Jeffrey Masek, Valeriy Kovalskyy

United States National Aeronautics and Space Administration: Publications

The potential of Landsat data processing to provide systematic continental scale products has been demonstrated by several projects including the NASA Web-enabled Landsat Data (WELD) project. The recent free availability of Landsat data increases the need for robust and efficient atmospheric correction algorithms applicable to large volume Landsat data sets. This paper compares the accuracy of two Landsat atmospheric correction methods: a MODIS-based method and the Landsat Ecosystem Disturbance Adaptive Processing System (LEDAPS) method. Both methods are based on the 6SV radiative transfer code but have different atmospheric characterization approaches. The MODIS-based method uses the MODIS Terra derived dynamic aerosol …

Optic Disc Edema, Globe Flattening, Choroidal Folds, And Hyperopic Shifts Observed In Astronauts After Long-Duration Space Flight, Thomas H. Mader, C. Robert Gibson, Anastas F. Pass, Larry A. Kramer, Andrew G. Lee, Jennifer Fogarty, William J. Tarver, Joseph P. Dervay, Douglas R. Hamilton, Ashot Sargsyan, John L. Phillips, Duc Tran, William Lipsky, Jung Choi, Claudia Stern, Raffi Kuyumjian, James D. Polk

United States National Aeronautics and Space Administration: Publications

Purpose: To describe the history, clinical findings, and possible etiologies of ophthalmic findings discovered in 7 astronauts after long-duration space flight, and document vision changes in approximately 300 additional astronauts.

Design: Retrospective, observational examination of ophthalmic findings in 7 astronauts and analysis of postflight questionnaires regarding in-flight vision changes in approximately 300 additional astronauts.

Participants: Seven astronauts with ophthalmic anomalies upon return from long-duration space missions to the International Space Station and 300 additional astronauts who completed postflight questionnaires regarding in-flight vision changes.

Methods: Before and after long-duration space flight, all 7 subjects underwent complete eye …

High Order Finite Difference Methods With Subcell Resolution For Advection Equations With Stiff Source Terms, Wei Wang, Chi-Wang Shu, H.C. Yee, Björn Sjögreen

United States National Aeronautics and Space Administration: Publications

A new high order finite-difference method utilizing the idea of Harten ENO subcell resolution method is proposed for chemical reactive flows and combustion. In reaction problems, when the reaction time scale is very small, e.g., orders of magnitude smaller than the fluid dynamics time scales, the governing equations will become very stiff. Wrong propagation speed of discontinuity may occur due to the underresolved numerical solution in both space and time. The present proposed method is a modified fractional step method which solves the convection step and reaction step separately. In the convection step, any high order shock-capturing method can be …

The Radiation Quality Factor As An Ornstein-Uhlenbeck Process, A. F. Barghouty

United States National Aeronautics and Space Administration: Publications

Radiation protection strategies for extended or deep space missions rely on accurate and robust estimates of exposure dose and corresponding risk to crew health, systems functions, and mission safety in general. Simulation and modeling of dose and risk associated with such exposures are, to various degrees, made difficult by the inherent complexity and variability in characterizing the radiation environment, its passage and interaction with matter, and its biological effects. One of the more important contributors to the overall uncertainty in dose or risk assessment is the empirical variability in the radiation quality factor, Q, which is typically used to differentiate …