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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1940

Flow around wings accompanied by separation of vortices

The flow around wings computed by the usual method leads in the case of a finite trailing edge to a stagnation point in the trailing edge due to the Kutta-Joukowsky condition of flow governing this region. As a result, the theoretical pressure distribution differs substantially from the experimental values in the vicinity of the trailing edge. The present report describes an alternative method of calculation in which the rear stagnation point no longer appears. The stream leaves the trailing edge tangentially on the pressure side and a similar tangential separation occurs on the suction side of the profile at a point slightly in front of the trailing edge.

Schmieden, C↗

NASA NTRS1992

NAS technical summaries: Numerical aerodynamic simulation program, March 1991 - February 1992

NASA created the Numerical Aerodynamic Simulation (NAS) Program in 1987 to focus resources on solving critical problems in aeroscience and related disciplines by utilizing the power of the most advanced supercomputers available. The NAS Program provides scientists with the necessary computing power to solve today's most demanding computational fluid dynamics problems and serves as a pathfinder in integrating leading-edge supercomputing technologies, thus benefiting other supercomputer centers in Government and industry. This report contains selected scientific results from the 1991-92 NAS Operational Year, March 4, 1991 to March 3, 1992, which is the fifth year of operation. During this year, the scientific community was given access to a Cray-2 and a Cray Y-MP. The Cray-2, the first generation supercomputer, has four processors, 256 megawords of central memory, and a total sustained speed of 250 million floating point operations per second. The Cray Y-MP, the second generation supercomputer, has eight processors and a total sustained speed of one billion floating point operations per second. Additional memory was installed this year, doubling capacity from 128 to 256 megawords of solid-state storage-device memory. Because of its higher performance, the Cray Y-MP delivered approximately 77 percent of the total number of supercomputer hours used during this year.

Source record↗

NASA NTRS1993

Numerical prediction of transition of the F-16 wing at supersonic speeds

A parametric study is being conducted as an effort to numerically predict the extent of natural laminar flow (NLF) on finite swept wings at supersonic speeds. This study is one aspect of a High Speed Research Program (HSRP) to gain an understanding of the technical requirements for high-speed aircraft flight. The parameters that are being addressed in this study are Reynolds number, angle of attack, and leading-edge wing sweep. These parameters were analyzed through the use of an advanced Computational Fluid Dynamics (CFD) flow solver, specifically the ARC 3-D Compressible Navier-Stokes (CNS) flow solver. From the CNS code, pressure coefficients (Cp) are obtained for the various cases. These Cp's are then used to compute the boundary-layer profiles through the use of the 'Kaups and Cebeci' compressible 2-D boundary layer code. Finally, the boundary-layer parameters are processed into a 3-D compressible boundary layer stability code (COSAL) to predict transition. The parametric study then consisted of four geometries which addressed the effects of sweep, and three angles of attack from zero to ten degrees to yield a total of 12 cases. The above process was substantially automated through a procedure that was developed by the work conducted under this study. This automation procedure then yields a 3-D graphical measure of the extent of laminar flow by predicting the transition location of laminar to turbulent flow.

Cummings, Russell M.↗

NASA NTRS1993

Analysis of local delaminations caused by angle ply matrix cracks

Two different families of graphite/epoxy laminates with similar layups but different stacking sequences, (0,theta,-theta) sub s and (-theta/theta/0) sub s were analyzed using three-dimensional finite element analysis for theta = 15 and 30 degrees. Delaminations were modeled in the -theta/theta interface, bounded by a matrix crack and the stress free edge. The total strain energy release rate, G, along the delamination front was computed using three different techniques: the virtual crack closure technique (VCCT), the equivalent domain Integral (EDI) technique, and a global energy balance technique. The opening fracture mode component of the strain energy release rate, Gl, along the delamination front was also computed for various delamination lengths using VCCT. The effect of residual thermal and moisture stresses on G was evaluated.

Salpekar, Satish A.↗

NASA NTRS1994

NAS technical summaries. Numerical aerodynamic simulation program, March 1992 - February 1993

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NASA NTRS1995

NAS Technical Summaries, March 1993 - February 1994

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NASA NTRS1994

X-ray refelection from photoionized media in active galactic nuclei

We calculate the spectrum of X-ray radiation and reprocessed by a partly ionized optically thick medium in an active galactic nucleus. We self-consistently calculate the ionization balance and thermal balance in the medium along with the distribution of X-ray intensity with optical depth. In addition to absorption or scattering of the incident X-rays, we also compute the spectrum of X-rays emitted by the material, including lines, edges, and bremsstrahlung. The albedo of the medium depends primarily on the X-ray ionization parameter (ratio of incident flux to gas density, zeta(sub Chi), and secondarily on the UV flux generated by dissipation inside the disk; we locate the critical range of zeta(sub Chi) over which the albedo increases from small to nearly unity. While the continuum reflection is very weak below 10 keV when zeta(sub Chi) is small, significnat fluxes are emitted in atomic lines and edges in this energy range. In the limit of large zeta(sub Chi), the albedo below 10 keV increases, but reflection in this band is never gray: some photoelectric absorption remains up to rather large values of zeta(sub Chi), while at still higher values, inverse Compton scattering amplifies the soft X-ray flux. These features are sufficiently sharp that current and near-future X-ray experiments should permit diagnostic measures of zeta(sub Chi).

Zycki, Piotr T.↗

NASA NTRS1992

Fluid Dynamic and Stability Analysis of a Thin Liquid Sheet

Interest in thin sheet flows has recently been renewed due to their potential application in space radiators. Theoretical and experimental studies of the fluid dynamics and stability of thin liquid sheet flows have been carried out in this thesis. A computer program was developed to determine the cross-sectional shape of the edge cylinder given the cross-sectional area of the edge cylinder. A stability analysis was performed on a non-planer liquid sheet. A study was conducted to determine the effects of air resistance on the sheet.

McMaster, Matthew S.↗

NASA NTRS2014

Shielding Characteristics Using an Ultrasonic Configurable Fan Artificial Noise Source to Generate Modes - Experimental Measurements and Analytical Predictions

An Ultrasonic Configurable Fan Artificial Noise Source (UCFANS) was designed, built, and tested in support of the NASA Langley Research Center's 14x22 wind tunnel test of the Hybrid Wing Body (HWB) full 3-D 5.8% scale model. The UCFANS is a 5.8% rapid prototype scale model of a high-bypass turbofan engine that can generate the tonal signature of proposed engines using artificial sources (no flow). The purpose of the program was to provide an estimate of the acoustic shielding benefits possible from mounting an engine on the upper surface of a wing; a flat plate model was used as the shielding surface. Simple analytical simulations were used to preview the radiation patterns - Fresnel knife-edge diffraction was coupled with a dense phased array of point sources to compute shielded and unshielded sound pressure distributions for potential test geometries and excitation modes. Contour plots of sound pressure levels, and integrated power levels, from nacelle alone and shielded configurations for both the experimental measurements and the analytical predictions are presented in this paper.

Artifical Noise↗

NASA NTRS2015

Adapting the SpaceCube v2.0 Data Processing System for Mission-Unique Application Requirements

The SpaceCubeTM v2.0 system is a superior high performance, reconfigurable, hybrid data processing system that can be used in a multitude of applications including those that require a radiation hardened and reliable solution. This paper provides an overview of the design architecture, flexibility, and the advantages of the modular SpaceCube v2.0 high performance data processing system for space applications. The current state of the proven SpaceCube technology is based on nine years of engineering and operations. Five systems have been successfully operated in space starting in 2008 with four more to be delivered for launch vehicle integration in 2015. The SpaceCube v2.0 system is also baselined as the avionics solution for five additional flight projects and is always a top consideration as the core avionics for new instruments or spacecraft control. This paper will highlight how this multipurpose system is currently being used to solve design challenges of three independent applications. The SpaceCube hardware adapts to new system requirements by allowing for application-unique interface cards that are utilized by reconfiguring the underlying programmable elements on the core processor card. We will show how this system is being used to improve on a heritage NASA GPS technology, enable a cutting-edge LiDAR instrument, and serve as a typical command and data handling (CDH) computer for a space robotics technology demonstration.

Xilinx FPGA↗

NASA NTRS2017

Mission Use of the SpaceCube Hybrid Data Processing System

The award-winning SpaceCube v2.0 system is a high performance, reconfigurable, hybrid data processing system that can be used in a multitude of applications including those that require a radiation hardened and reliable solution. This presentation provides an overview of the design architecture, flexibility, and the advantages of the modular SpaceCube v2.0 high performance data processing system for space applications. The current state of the proven SpaceCube technology is based on 11 years of engineering and operations. Eight systems have been successfully operated in space starting in 2008 with eight more to be delivered for payload integration in 2018 in support of various missions. This presentation will highlight how this multipurpose system is currently being used to solve design challenges of a variety of independent applications. The SpaceCube hardware adapts to new system requirements by allowing for application-unique interface cards that are utilized by reconfiguring the underlying programmable elements on the core processor card. We will show how this system is being used to improve on a heritage NASA GPS technology, enable a cutting-edge LiDAR instrument, and serve as a typical command and data handling (CDH) computer for a space robotics technology demonstration.Finally, this presentation will highlight the use of the SpaceCube v2.0 system on the Restore-L robotic satellite servicing mission. SpaceCube v2.0 is the central avionics responsible for the real-time vision system and autonomous robotic control necessary to find, capture, and service a national asset weather satellite.

Petrick, Dave↗

NASA NTRS1995

Progress in Navier-Stokes Simulation of Delta Wing Maneuver Aerodynamics

This paper will summarize recent progress in the numerical simulation of high incidence vortical flow about a generic 65 degree sweep delta wing using the three dimensional, time-dependent, Reynolds averaged, Navier-Stokes (RANS) equations. Computations have been carried out at 15 and 30 degrees angle of attack under subsonic turbulent flow conditions, and compared with experimental data provided by Hanff, Jenkins, and their colleagues. This work has already been published elsewhere and widely disseminated. Computations carried out at 15 degrees angle of attack included static roll angles ranging up to 65 degrees, and a large-amplitude (40 degree), high rate (7 Hz), forced roll motion. There was very good agreement between computed and experimental forces and moments, and static surface pressures. There was a significant hysteresis of the dynamic rolling moment due to the high rate of roll motion. At this angle of attack, no vortex breakdown was observed in the computations or experiment. Computations were also carried out at 30 degrees angle of attack, where vortex breakdown was present in both the computations and experiment. There was overall good agreement in the computed and experimental forces and moments. The static rolling moment varied with roll angle in a highly nonlinear manner, and exhibited three stable trim points and two unstable trim points. This behavior was attributed to the presence of vortex breakdown. Two large-amplitude (30 degrees), high-rate (10 Hz) forced roll motions were computed. The dynamics of the vortex breakdown motion was dramatically visualized by tracking the time-dependent motion of particles released near the delta wing apex. This numerical visualization is analogous to experimental smoke flow techniques. In one of the dynamic cases the breakdown was found to move off the wing, convected downwind of the trailing edge, and later reformed near the trailing edge through an instability of the vortex core. A damped free-to-roll motion was also computed by releasing the wing from rest at 40 degrees of roll. The wing went to the same trim point as in the experiment.

Chaderjian, Neal M.↗

NASA NTRS1988

Euler/Navier-Stokes zonal scheme with applications to separated and isolated-vortex flows

An Euler/Navier-Stokes zonal scheme with boundary-layer compatibility conditions is developed to economically compute separated and vortex flows. The scheme is based on dividing the flow region into zones, where different levels of mathematical approximations of the governing equations are used in each zone. The scheme is applied to two specific problems: the two dimensional flow over a blunt leading-edge plate and the quasi-axisymmetric flow of an isolated vortex core. In the first problem, the computational domain is divided into inner and outer zones where the Navier-Stokes and Euler equations are used, respectively. On the downstream boundary of the computational domain, boundary-layer compatibility conditions are used. In the second problem, boundary-layer-like equations for slender, compressible, vortex flows are developed. A compatibility condition has been used to ensure consistency of the boundary and initial conditions. The outer boundary conditions of the flow are derived from Euler equations for a stream surface.

Kandil, Osama A.↗

DOE OSTI2025

DUNE Software and Computing Research and Development

The international collaboration designing and constructing the Deep Underground Neutrino Experiment (DUNE) at the Long-Baseline Neutrino Facility (LBNF) has developed a two-phase strategy toward the implementation of this leading-edge, large-scale science project. The ambitious physics program of Phase I and Phase II of DUNE is dependent upon deployment and utilization of significant computing resources, and successful research and development of software (both infrastructure and algorithmic) in order to achieve these scientific goals. This submission discusses the computing resources projections, infrastructure support, and software development needed for DUNE during the coming decades as an input to the European Strategy for Particle Physics Update for 2026. The DUNE collaboration is submitting four main contributions to the 2026 Update of the European Strategy for Particle Physics process. This submission to the 'Computing' stream focuses on DUNE software and computing. Additional inputs related to the DUNE science program, DUNE detector technologies and R&D, and European contributions to Fermilab accelerator upgrades and facilities for the DUNE experiment, are also being submitted to other streams.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

NASA NTRS1977

Computation of the temperature distribution in cooled radial inflow turbine guide vanes

A two-dimensional finite-difference numerical technique is presented to determine the temperature distribution of an internally-cooled blade of radial turbine guide vanes. A simple convection cooling is assumed inside the guide vane. Such an arrangement results in relatively small cooling effectiveness at the leading edge and at the trailing edge. Heat transfer augmentation in these critical areas may be achieved by using impingement jets and film cooling. A computer program is written in Fortran IV for IBM 370/165 computer.

Tabakoff, W.↗

DOE OSTI2019

Parafermions, induced edge states, and domain walls in fractional quantum Hall effect spin transitions

Search for parafermions and Fibonacci anyons, which are excitations obeying non-Abelian statistics, is driven both by the quest for deeper understanding of nature and prospects for universal topological quantum computation. However, physical systems that can host these exotic excitations are rare and hard to realize in experiments. Here we study the domain walls and the edge states formed in spin transitions in the fractional quantum Hall effect. Effective theory approach and exact diagonalization in a disk and torus geometries proves the existence of the counterpropagating edge modes with opposite spin polarizations at the boundary between the two neighboring regions of the two-dimensional electron liquid in spin-polarized and spin-unpolarized phases. By analytical and numerical analysis, we argue that these systems can host parafermions when coupled to an 𝑠-wave superconductor and are experimentally feasible. We investigate settings based on 𝜈 = 2/3, 4/3, and 5/3 spin transitions and analyze spin-flipping interactions that hybridize counterpropagating modes. Lastly, we discuss spin-orbit interactions of composite fermions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

NASA NTRS2003

PLIF Temperature and Velocity Distributions in Laminar Hypersonic Flat-plate Flow

Rotational temperature and velocity distributions have been measured across a hypersonic laminar flat-plate boundary layer, using planar laser-induced fluorescence. The measurements are compared to a finite-volume computation and a first-order boundary layer computation, assuming local similarity. Both computations produced similar temperature distributions and nearly identical velocity distributions. The disagreement between calculations is ascribed to the similarity solution not accounting for leading-edge displacement effects. The velocity measurements agreed to within the measurement uncertainty of 2 % with both calculated distributions. The peak measured temperature was 200 K lower than the computed values. This discrepancy is tentatively ascribed to vibrational relaxation in the boundary layer.

OByrne, S.↗

DOE OSTI2022

Differentially Private Synthesis and Sharing of Network Data Via Bayesian Exponential Random Graph Models

Abstract Network data often contain sensitive relational information. One approach to protecting sensitive information while offering flexibility for network analysis is to share synthesized networks based on the information in originally observed networks. We employ differential privacy (DP) and exponential random graph models (ERGMs) and propose the DP-ERGM method to synthesize network data. We apply DP-ERGM to two real-world networks. We then compare the utility of synthesized networks generated by DP-ERGM, the DyadWise Randomized Response (DWRR) approach, and the Synthesis through Conditional distribution of Edge given nodal Attribute (SCEA) approach. In general, the results suggest that DP-ERGM preserves the original information significantly better than two other approaches in network structural statistics and inference for ERGMs and latent space models. Furthermore, DP-ERGM satisfies node DP through modeling the global network structure with ERGM, a stronger notion of privacy than the edge DP under which DWRR and SCEA operate.

graph synthesis↗