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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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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

A CFD Assessment of Several High-Lift Reference H Configuration Using Structured Grids

The objective of this study is to calibrate a Navier-Stokes code for a high-lift Reference H configuration using structured grids. The outline of this presentation will first include a brief description of the grids used and the flow solver. Next the results will be presented in terms of convergence and resources used on the C-90. Predicted force and moment and surface pressure results are compared to experiment and off- and on-surface flow viz. is discussed.

Lessard, Wendy B.↗
DOE OSTI2022

QForte: An Efficient State-Vector Emulator and Quantum Algorithms Library for Molecular Electronic Structure

Here, we introduce a novel open-source software package QForte, a comprehensive development tool for new quantum simulation algorithms. QForte incorporates functionality for handling molecular Hamiltonians, fermionic encoding, ansatz construction, time evolution, and state-vector emulation, requiring only a classical electronic structure package as a dependency. QForte also contains black-box implementations of a wide variety of quantum algorithms, including variational and projective quantum eigensolvers, adaptive eigensolvers, quantum imaginary time evolution, and quantum Krylov methods. We highlight two features of QForte: (i) how the Python class structure of QForte enables the facile implementation of new algorithms, and (ii) how existing algorithms can be executed in just a few lines of code.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Predicting hot electron generation in inertial confinement fusion with particle-in-cell simulations

A series of two-dimensional particle-in-cell simulations with speckled laser drivers was carried out to study hot electron generation in direct-drive inertial confinement fusion on OMEGA. Scaling laws were obtained for hot electron fraction and temperature as functions of laser/plasma conditions in the quarter-critical region. Using these scalings and conditions from hydro simulations, the temporal history of hot electron generation can be predicted. The scalings can be further improved to predict hard x-rays for a collection of OMEGA warm target implosions within experimental error bars. Furthermore, these scalings can be readily implemented into inertial confinement fusion design codes.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Utilizing the deuterium-tritium fusion resonance to diagnose thermal runaway in igniting plasmas

For high-efficiency inertial confinement fusion implosions, it is predicted that a burning hot spot will successfully encompass all surrounding fuel and then transition into a thermal runaway where the internal energy increase from fusion occurs on a timescale faster than the expansion of the fuel is able to quench the fusion chain reaction after ignition occurs. Observation of this dynamic phase transition would indicate distinct burn properties and indicate an implosion's robustness. A technique for diagnosing the presence of thermal runaway from measurements of nuclear reaction history is presented. The technique is based on taking the logarithmic derivative of the nuclear reaction history, called the 𝛼 curve, and allowing a mathematical decoupling of the mass, volume, and thermal reactivity in the fusion reaction rate equation. During thermal runaway, where the thermal temperature dominates the burn dynamics, a maximum in the 𝛼 curve is found where there is a maximum in the first derivative of the thermal fusion reactivity, an effect to the deuterium-tritium (DT) fusion cross-section resonance. This provides a distinct signature related to the fundamental nature of the DT fusion nuclear resonance and signifies the transition into the fusion thermal instability. Impacts of charged particle transport on the effect are also assessed and the analytical formulas are compared and found to be in agreement with radiation hydrodynamic codes.

high-energy-density plasmas↗
DOE OSTI2022

NRAP-Open-IAM: Generic Aquifer Component Development and Testing

The Generic Aquifer Model calculates the concentrations of dissolved salt and dissolved CO 2 surrounding a leaking legacy well. The Generic Aquifer model can also estimate the size of an “impact plume” where concentration changes exceed user-specified thresholds. The model is a component of NRAP-Open-IAM, an open-source Integrated Assessment Model (IAM) developed by the National Risk Assessment Partnership (NRAP) to perform risk assessment for geologic CO 2 storage. The input parameters were selected to cover a wide range of groundwater aquifers and leakage rates. The generic aquifer model was developed using a generative adversarial deep learning network, trained using a large synthetic dataset of STOMP multiphase flow simulations. The deep learning model predictions of dissolved salt and dissolved CO 2 in the aquifer compare well to the original STOMP simulation results. The extent of aquifer impacted by leaking CO 2 or brine is calculated using a user-defined mass fraction threshold. The aquifer impact volumes calculated based on STOMP simulation results compare well to those calculated based on the deep learning model. In a provided python script, gridded observation results from the generic aquifer component of NRAP-Open-IAM are converted to HDF5 format files for monitoring design with the DREAM code.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1976

Data compression for satellite images

An efficient data compression system is presented for satellite pictures and two grey level pictures derived from satellite pictures. The compression techniques take advantages of the correlation between adjacent picture elements. Several source coding methods are investigated. Double delta coding is presented and shown to be the most efficient. Both predictive differential quantizing technique and double delta coding can be significantly improved by applying a background skipping technique. An extension code is constructed. This code requires very little storage space and operates efficiently. Simulation results are presented for various coding schemes and source codes.

Chen, P. H.↗
NASA NTRS1977

Reliability measurement during software development

Measurement of software reliability was carried out during the development of data base software for a multi-sensor tracking system. Every run made during this project was scored as success or failure, and supporting data were collected on forms for further analysis. The failure ratio (number of failures per calendar interval divided by total number of runs) and failure rate (number of failures divided by CPU time for the interval) were found to be consistent measures, on a month-to-month basis as well as from module to module, and therefore considered valid indicators of reliability in this environment. Trend lines could be established from these measurements that provide good visualization of the progress on the job as a whole as well as on individual modules. Over one-half of the observed failures were due to factors associated with the specific run submission rather than with the code proper.

Hecht, H.↗
NASA NTRS1981

Enhancement of peptide bond formation by polyribonucleotides on clay surfaces in fluctuating environments

The selective effects of polyribonucleotides on the formation of glycine peptide bonds in glycine on clay surfaces are investigated as a model for a template mechanism for the effects of polynucleotides on peptide bond formation. Free oligoglycine yields were determined for the cycling reaction of glycine in the presence and absence of clay and polyribonucleotides or polydeoxyribonucleotides. The polyribonucleotides are observed to lead to increases of up to fourfold increases in oligoglycine formed, with greater enhancements for poly-G nucleotides than for poly-A, poly-U and poly-C, indicating a codonic bias. Polydeoxyribonucleotides are found to provide no enhancement in peptide formation rates, and yields were also greatly reduced in the absence of clay. A mechanism for peptide synthesis is proposed which involves the activation of glycine on the clay surface, followed by the formation of esters between glycine and the 2-prime OH groups of the polyribonucleotide and peptide bonds between adjacent amino acyl esters. It is pointed out that if this mechanism is correct, it may provide a basis for a direct template translation process, which would produce a singlet genetic code.

White, D. H.↗
NASA NTRS1980

Capacity of a direct detection optical communication channel

The capacity of a free space optical channel using a direct detection receiver is derived under both peak and average signal power constraints and without a signal bandwidth constraint. The addition of instantaneous noiseless feedback from the receiver to the transmitter does not increase the channel capacity. In the absence of received background noise, an optimally coded PPM system is shown to achieve capacity in the limit as signal bandwidth approaches infinity. In the case of large peak to average signal power ratios, an interleaved coding scheme with PPM modulation is shown to have a computational cutoff rate far greater than ordinary coding schemes.

Tan, H. H.↗
NASA NTRS1983

PREWATE: An interactive preprocessing computer code to the Weight Analysis of Turbine Engines (WATE) computer code

The Weight Analysis of Turbine Engines (WATE) computer code was developed by Boeing under contract to NASA Lewis. It was designed to function as an adjunct to the Navy/NASA Engine Program (NNEP). NNEP calculates the design and off-design thrust and sfc performance of User defined engine cycles. The thermodynamic parameters throughout the engine as generated by NNEP are then combined with input parameters defining the component characteristics in WATE to calculate the bare engine weight of this User defined engine. Preprocessor programs for NNEP were previously developed to simplify the task of creating input datasets. This report describes a similar preprocessor for the WATE code.

Fishbach, L. H.↗
NASA NTRS1985

Recent improvements in efficiency, accuracy, and convergence for implicit approximate factorization algorithms

In 1977 and 1978, general purpose centrally space differenced implicit finite difference codes in two and three dimensions have been introduced. These codes, now called ARC2D and ARC3D, can run either in inviscid or viscous mode for steady or unsteady flow. Since the introduction of the ARC2D and ARC3D codes, overall computational efficiency could be improved by making use of a number of algorithmic changes. These changes are related to the use of a spatially varying time step, the use of a sequence of mesh refinements to establish approximate solutions, implementation of various ways to reduce inversion work, improved numerical dissipation terms, and more implicit treatment of terms. The present investigation has the objective to describe the considered improvements and to quantify advantages and disadvantages. It is found that using established and simple procedures, a computer code can be maintained which is competitive with specialized codes.

Pulliam, T. H.↗
NASA NTRS1989

High rate concatenated coding systems using multidimensional bandwidth-efficient trellis inner codes

A concatenated coding system using two-dimensional trellis-coded MPSK inner codes and Reed-Solomon outer codes for application in high-speed satellite communication systems was proposed previously by the authors (1989). The authors extend their results to systems using symbol-oriented, multidimensional, trellis-coded MPSK inner codes. The concatenated coding systems are divided into two classes according to their achievable effective information rates. The first class uses multidimensional trellis-coded 8-PSK inner codes and achieves effective information rates around 1 b/dimension (spectral efficiency 2 b/s/Hz). The second class employs multidimensional trellis-coded 16-PSK inner codes and provides effective information rates around 1.5 b/dimension (spectral efficiency 3 b/s/Hz). Both classes provide significant coding gains over an uncoded reference system with the same effective information rate as the coded system. The results show that the symbol-oriented nature of multidimensional inner codes can provide an improvement of up to 1 dB in the overall performance of a concatenated coding system when these codes replace bit-oriented two-dimensional codes.

Deng, Robert H.↗
NASA NTRS1991

Group evaporation

Liquid fuel combustion process is greatly affected by the rate of droplet evaporation. The heat and mass exchanges between gas and liquid couple the dynamics of both phases in all aspects: mass, momentum, and energy. Correct prediction of the evaporation rate is therefore a key issue in engineering design of liquid combustion devices. Current analytical tools for characterizing the behavior of these devices are based on results from a single isolated droplet. Numerous experimental studies have challenged the applicability of these results in a dense spray. To account for the droplets' interaction in a dense spray, a number of theories have been developed in the past decade. Herein, two tasks are examined. One was to study how to implement the existing theoretical results, and the other was to explore the possibility of experimental verifications. The current theoretical results of group evaporation are given for a monodispersed cluster subject to adiabatic conditions. The time evolution of the fluid mechanic and thermodynamic behavior in this cluster is derived. The results given are not in the form of a subscale model for CFD codes.

Shen, Hayley H.↗
NASA NTRS1992

Ballistic limit regression analysis for Space Station Freedom meteoroid and space debris protection system

Relationships defining the ballistic limit of Space Station Freedom's (SSF) dual wall protection systems have been determined. These functions were regressed from empirical data found in Marshall Space Flight Center's (MSFC) Hypervelocity Impact Testing Summary (HITS) for the velocity range between three and seven kilometers per second. A stepwise linear least squares regression was used to determine the coefficients of several expressions that define a ballistic limit surface. Using statistical significance indicators and graphical comparisons to other limit curves, a final set of expressions is recommended for potential use in Probability of No Critical Flaw (PNCF) calculations for Space Station. The three equations listed below represent the mean curves for normal, 45 degree, and 65 degree obliquity ballistic limits, respectively, for a dual wall protection system consisting of a thin 6061-T6 aluminum bumper spaced 4.0 inches from a .125 inches thick 2219-T87 rear wall with multiple layer thermal insulation installed between the two walls. Normal obliquity is d(sub c) = 1.0514 v(exp 0.2983 t(sub 1)(exp 0.5228). Forty-five degree obliquity is d(sub c) = 0.8591 v(exp 0.0428) t(sub 1)(exp 0.2063). Sixty-five degree obliquity is d(sub c) = 0.2824 v(exp 0.1986) t(sub 1)(exp -0.3874). Plots of these curves are provided. A sensitivity study on the effects of using these new equations in the probability of no critical flaw analysis indicated a negligible increase in the performance of the dual wall protection system for SSF over the current baseline. The magnitude of the increase was 0.17 percent over 25 years on the MB-7 configuration run with the Bumper II program code.

Jolly, William H.↗
NASA NTRS1992

Previous model comparisons

The first model comparison workshop examined 14 mathematical models. Issues discussed included: transport methodologies; transport of nuclear test debris; transport algorithms; source gases; NO(y), Cl(x), HO(x), and O3; photolysis rates; diurnal averaging; and rainout. The second model comparison meeting examined 16 models. More real model-model intercomparisons were undertaken and several topics were addressed including: photochemistry and radiation; transport; current atmosphere 1980; and assessment runs. The models computed different values for photolysis rates even when O3 and O2 were fixed, thus more time should be spent at future model comparison meeting on radiation codes.

Jackman, Charles H.↗
NASA NTRS1992

HSR combustion analytical research

Increasing the pressure and temperature of the engines of a new generation of supersonic airliners increases the emissions of nitrogen oxides (NO(x)) to a level that would have an adverse impact on the Earth's protective ozone layer. In the process of evolving and implementing low emissions combustor technologies, NASA LeRC has pursued a combustion analysis code program to guide combustor design processes, to identify potential concepts of the greatest promise, and to optimize them at low cost, with short turnaround time. The computational analyses are evaluated at actual engine operating conditions. The approach is to upgrade and apply advanced computer programs for gas turbine applications. Efforts were made in further improving the code capabilities for modeling the physics and the numerical methods of solution. Then test cases and measurements from experiments are used for code validation.

Nguyen, H. Lee↗