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DOE OSTI2020

Comparison of plug flow and multi-node stratified tank modeling approaches regarding computational efficiency and accuracy

Residential water heaters contain water stratified by temperature-driven density differences. This implies that a water tank can reach a state in which the top and bottom sections have different temperatures, unless mixing happens. A high degree of thermal stratification can improve the efficiency of some water heaters, by saving the amount of energy required for the heat-up process. Studies of stratification became popular in the 1970s and it remains an active research topic today. The research has led to the development of different models and techniques to better predict and define a stratified tanks behavior. By comparing these models and techniques used previously to describe thermal stratification, the phenomenon could be better understood, exploited, and used to increase efficiency and thermal energy capacity in modern water tanks. From the existing models, we found the one-dimensional standard plug-flow and a multi node model to be appropriate for analyzing the processes of the heat up and cool-down in a water tank. These two models are based on energy balances. This work involved comparing the accuracy and computational effort needed to implement these models. To assess accuracy, we compared both types of existing models to experimental data (also collected in this work) which included a heat up process using an external heat pump. This external process included a layering process that has an eddy diffusivity at five times the rate of thermal diffusion. For this project, we implemented the models in MATLAB, the multi-paradigm numerical computing environment. We quantified model accuracy using the root mean squared error between modeled data and experimental data for six measured tank temperatures. Comparing the accuracy and the computational time taken to run the simulation provides a method to contrast the performance of each model and a way to rate it. The multi node model was run using from 6 to 96 spatial nodes; the plug flow model was run using 1 to 0.001 º C temperature bin sizes. Additionally, timesteps were varied from 4 to 236 s. The results quantify the tradeoff between accuracy and computational time, providing guidance for simulations to intelligently select the best model type and simulation parameters. This research can be used to validate the pre-existing models and possibly improve the modern water tank.

Bulnes, Fernando Karg↗

NASA NTRS1986

NASA-Chinese Aeronautical Establishment (CAE) Symposium

Several topics relative to combustion research are discussed. A numerical study of combustion processes in afterburners; the modeling of turbulent, reactive flow; gas turbine research; modeling of dilution jet flow fields; and chemical shock tubes as tools for studying high-temperature chemical kinetics are among the topics covered.

Source record↗

DOE OSTI2019

Proceedings of the 10th US/German Workshop on Salt Repository Research Design and Operation. Rev. 1

The 10th US/German Workshop on Salt Repository Research, Design, and Operation was hosted by RESPEC and South Dakota School of Mines & Technology, both located in the Black Hills of South Dakota. Over 60 registered participants representing Germany, United States, the Netherlands, and the United Kingdom availed themselves to excellent facilities on the School of Mines campus. As the 10th annual workshop, this occasion is a milestone of the modern era of collaboration between the US and Germany, which has extended to other countries with potential for radioactive waste disposal in salt. Thrust areas covered in the annual workshops are selected by participants and typically include elements of continuity from year to year. This year's themes included siting, modeling challenges, seal systems and materials, operational safety, and special topics. Two major breakout sessions addressed test sample conditioning and natural closure of salt openings. When the new-generation US/German workshops were conceived, one goal was to identify challenging issues related to salt repository sciences and then conduct open discussions in special breakout sessions. These timely sessions achieve the workshop paradigm and provide in-depth dialogue on important salt repository considerations. In many respects, general themes of these salt repository workshops reflect advances in the scientific basis for nuclear-waste disposal in salt formations and develop naturally as a consequence of unremitting attention largely as a result of the workshop commitment. Technical capabilities in the laboratory and field continue to improve in concert with accumulating experience. Because we are working together, mechanical deformation at the micro-scale can be interpreted at a large scale, which is fundamental to predictive modeling of salt repository evolution. This document records the Proceedings of the 2019 gathering of salt repository nations and has been compiled by RESPEC, demonstrating an adopted protocol in which the host organization creates that year's Proceedings. To assist with organization and compilation, individual chapters are summarized by volunteer subject-matter experts from the participatory audience; these contributors are recognized in the Acknowledgements. All formal presentations are included in this document, thus providing a resource for referencing and many excellent photographic images. Appendices include the agenda, list of participants, abstracts, and presentations. A primary purpose for recording workshop activities is to create and sustain an accessible record of salt repository research. These archives also illustrate transparent development of research areas each year.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2014

Absorption of ethanol, acetone, benzene and 1,2-dichloroethane through human skin in vitro: a test of diffusion model predictions

The overall goal of this research was to further develop and improve an existing skin diffusion model by experimentally confirming the predicted absorption rates of topically-applied volatile organic compounds (VOCs) based on their physicochemical properties, the skin surface temperature, and the wind velocity. In vitro human skin permeation of two hydrophilic solvents (acetone and ethanol) and two lipophilic solvents (benzene and 1,2-dichloroethane) was studied in Franz cells placed in a fume hood. Four doses of each {sup 14}C-radiolabed compound were tested — 5, 10, 20, and 40 μL cm{sup −2}, corresponding to specific doses ranging in mass from 5.0 to 63 mg cm{sup −2}. The maximum percentage of radiolabel absorbed into the receptor solutions for all test conditions was 0.3%. Although the absolute absorption of each solvent increased with dose, percentage absorption decreased. This decrease was consistent with the concept of a stratum corneum deposition region, which traps small amounts of solvent in the upper skin layers, decreasing the evaporation rate. The diffusion model satisfactorily described the cumulative absorption of ethanol; however, values for the other VOCs were underpredicted in a manner related to their ability to disrupt or solubilize skin lipids. In order to more closely describe the permeation data, significant increases in the stratum corneum/water partition coefficients, K{sub sc}, and modest changes to the diffusion coefficients, D{sub sc}, were required. The analysis provided strong evidence for both skin swelling and barrier disruption by VOCs, even by the minute amounts absorbed under these in vitro test conditions. - Highlights: • Human skin absorption of small doses of VOCs was measured in vitro in a fume hood. • The VOCs tested were ethanol, acetone, benzene and 1,2-dichloroethane. • Fraction of dose absorbed for all compounds at all doses tested was less than 0.3%. • The more aggressive VOCs absorbed at higher levels than diffusion model predictions. • We conclude that even small exposures to VOCs temporarily alter skin permeability.

60 APPLIED LIFE SCIENCES↗

NASA NTRS1988

Aircraft aeroelasticity and structural dynamics research at the NASA Langley Research Center: Some illustrative results

Highlights of nine different research studies are described. Five of these topics relate directly to fixed-wing aircraft and range from flutter studies using relatively simple and inexpensive wind-tunnel models to buffet studies of the vertical tails of an advanced high performance configuration. The other four topics relate directly to rotary-wing aircraft and range from studies of the performance and vibration characteristics of an advanced rotor design to optimization of airframe structures for vibration attenuation.

Doggett, Robert V., Jr.↗

DOE OSTI2026

A stress-based fracture model for reacting metal ejecta

The evolution of reacting metal ejecta continues to be a topic of interest at the forefront of metals in reactive and extreme environments. Ejecta are small particles formed when the surface of a metal undergoes Richtmyer–Meshkov instability from a strong shock. Experiments have shown that in the case where ejecta are in ambient conditions that induce a reaction, the ejecta behave irregularly. The ejecta temperature rises and then plateaus, and the acceleration profile shows unexpected jumps. These variations are assumed to be related to the exothermic heat release and particle mass loss caused by the reaction. To explain this phenomenon, efforts to model this in simulations have increased. While current models can capture many of these physical processes, they currently assign a constant reaction shell thickness with little physical reasoning. This work remedies this problem by assigning a dynamic physically informed shell thickness to the reacting particles, using solid analysis. The shell thickness of the particles impacts the rate of change of reacted mass in the system, as well as the rate at which the particles react. The model is based on a simple stress–strain relationship and gives a dynamic assignment for when the reacting particle should begin to fracture. We compare our model to the previous computational and simulation data to analyze the effects of different model parameters.

42 ENGINEERING↗

NASA NTRS1999

Propagation Effects of Importance to the NASA/JPL Deep Space Network (DSN)

This paper presents Propagation Effects of Importance To The NASA/JPL Deep Space Network (DSN). The topics include: 1) DSN Antennas; 2) Deep Space Telecom Link Basics; 3) DSN Propagation Region of Interest; 4) Ka-Band Weather Effects Models and Examples; 5) Existing Goldstone Ka-Band Atmosphere Attenuation Model; 6) Existing Goldstone Atmosphere Noise Temperature Model; and 7) Ka-Band delta (G/T) Relative to Vacuum Condition. This paper summarizes the topics above.

Slobin, Steve↗

NASA NTRS1981

Parameter estimation of large flexible aerospace structures with application to the control of the Maypole Deployable Reflector

Systems such as the Maypole deployable reflector have a distributed parameter nature. The flexible column and hoop structure and the circular antenna of 30-100 meter diameter which it supports are described by partial, rather than ordinary, differential equations. Progress completed in reduced order modelling andd controller design and digital parameter estimation and control is summarized. Topics covered include depolyment and on-orbit operation; quasi-static (steady state) operation; dynamic distributed parameter system; autoregressive moving average identification; frequency domain procedures; direct or implicit active control; adaptive observers; parameter estimation using a linear reinforcement learning factor; feedback control; and reduced order modeling for nonlinear systems.

Balas, M. J.↗

NASA NTRS2000

A strategic systems perspective of organizational learning theory: models for a case study at the Jet Propulsion Laboratory

Organizational learning is an umbrella term that covers a variety of topics including; learning curves, productivity, organizational memory, organizational forgetting, knowledge transfer, knowledge sharing and knowledge creation. This treatise will review some of these theories in concert with a model of how organizations learn.

organizational learning strategy innovation design↗

NASA NTRSDate not supplied

Uncertainty in the response of sudden stratospheric warmings and stratosphere- troposphere coupling to quadrupled CO2 concentrations in CMIP6 models

Major sudden stratospheric warmings (SSWs), vortex formation and final breakdown dates are key highlight points of the stratospheric polar vortex. These phenomena are relevant for stratosphere-troposphere coupling, which explains the interest in understanding their future changes. However, up to now, there is not a clear consensus on which projected changes to the polar vortex are robust, particularly in the Northern Hemisphere, possibly due to short data record or relatively moderate CO2 forcing. The new simulations performed under the Coupled Model Intercomparison Project, Phase 6, together with the long daily data requirements of the DynVarMIP project in preindustrial and quadrupled CO2 (4xCO2 ) forcing simulations provide a new opportunity to revisit this topic by overcoming the limitations mentioned above. In this study, we analyze this new model output to document the change, if any, in the frequency of SSWs under 4xCO2 forcing. Our analysis reveals a large disagreement across the models as to the sign of this change, even though most models show a statistically significant change. The models, however, are in good agreement as to the impact of SSWs over the North Atlantic: there is no indication of a change under 4xCO2 forcing. Over the Pacific, however, the change is more uncertain. Finally, the models show robust changes to the seasonal cycle in the stratosphere. Specifically, we find a longer duration of the stratospheric polar vortex, and thus a longer season of stratosphere-troposphere coupling.

sudden stratospheric warmings (SSWs)↗

DOE OSTI2022

Recent Improvements in PV+Battery Modeling in NREL's System Advisor Model

This poster covers recent updates to the NREL System Advisor Model's battery model that can be coupled to the PV model to add value to both front of meter and behind the meter systems. Topics include new dispatch algorithms focusing on smoothing the output of a PV plant to meet ramp rate requirements and responding to price signals to maximize system revenue, validated battery lifetime models, grid outage simulations and resiliency metrics, and the new levelized cost of storage (LCOS) metric. We will also share preliminary results from NREL analysis projects using these features.

battery↗

NASA NTRS1990

Application of Lanczos vectors to control design of flexible structures

This report covers research conducted during the first year of the two-year grant. The research, entitled 'Application of Lanczos Vectors to Control Design of Flexible Structures' concerns various ways to obtain reduced-order mathematical models for use in dynamic response analyses and in control design studies. This report summarizes research described in several reports and papers that were written under this contract. Extended abstracts are presented for technical papers covering the following topics: controller reduction by preserving impulse response energy; substructuring decomposition and controller synthesis; model reduction methods for structural control design; and recent literature on structural modeling, identification, and analysis.

Craig, Roy R., Jr.↗

NASA NTRS1988

Aircraft aeroelasticity and structural dynamics research at the NASA Langley Research Center - Some illustrative results

Highlights of nine different research studies are described. Five of these topics relate directly to fixed-wing aircraft and range from flutter studies using relatively simple and inexpensive wind-tunnel models to buffet studies of the vertical tails of an advanced high-performance configuration. The other four topics relate directly to rotary-wing aircraft and range from studies of the performance and vibration characteristics of an advanced rotor design to optimization of airframe structures for vibration attenuation.

Doggett, Robert V., Jr.↗

NASA NTRS2024

Preface to the Special Issue on Modeling and Data Analysis Methods for the SMILE mission

The SMILE (Solar wind Magnetosphere Ionosphere Link Explorer) project (http://www.nssc.cas.cn/smile/, https://www.cosmos.esa.int/web/smile/mission) is a joint spacecraft mission of the European Space Agency (ESA) and the Chinese Academy of Sciences (CAS) with an expected launch in 2025. SMILE aims to study the global interactions of solar wind–magnetosphere–ionosphere innovatively by imaging the Earth’s magnetosheath and cusps in soft X-rays and the northern auroral region in ultraviolet (UV) while simultaneously measuring plasma and magnetic field parameters in the solar wind and magnetosheath along a highly-elliptical and highly-inclined orbit. This special issue is composed of 22 articles, presenting recent progress in modeling and data analysis techniques developed for the SMILE mission. In this preface, we categorize the articles into the following seven topics and provide brief summaries: (1) instrument descriptions of the Soft X-ray Imager (SXI), (2) numerical modeling of the X-ray signals, (3) data processing of the X-ray images, (4) boundary tracing methods from the simulated images, (5) physical phenomena and a mission concept related to the scientific goals of SMILE-SXI, (6) studies of the aurora, and (7) ground-based support for SMILE.

SMILE↗

DOE OSTI2021

How structural differences influence cross-model consistency: An electric sector case study

Multiple models are often employed to describe a range of possible outcomes for one or more scenarios, yielding insights into causal relationships and their uncertainties. Electric sector capacity expansion scenarios are a common topic of such efforts due to the economic influence of the electric sector, but model results typically span a broad solution space despite efforts to harmonize input assumptions, making decision implications difficult to discern. This study investigates the relationship between input harmonization and cross-model scenario consistency under disparate electric sector scenarios. We compare cross-model consistency between two state-of-the-art electric sector capacity expansion models (GCAM-USA and ReEDS) for six electric sector scenarios comprising alternate assumptions about fossil fuel resource availability, technology innovation, and long-term economy-wide transitions under four harmonization configurations varying model representations of electricity demand, fuel prices, renewable resources, and capacity retirements. These comparisons reveal that cross-model consistency can vary across scenarios under a given harmonization configuration, suggesting that harmonization efforts must often be scenario-specific if comparable cross-model consistency is desired. Model structural differences can hinder consistency, and the impact of these differences can depend on the scenario. Ultimately, thorough harmonization can reveal insights into cross-model consistency, which can be used to tighten uncertainty bounds and improve the decision-making implications of multi-model activities.

Cohen, Stuart↗

DOE OSTI2013

PACKAGE IMPACT MODELS AS A PRECURSOR TO CLADDING ANALYSIS

The evaluation of spent nuclear fuel storage casks and transportation packages under impact loading is an important safety topic that is reviewed as part of cask and package certification by the United States Nuclear Regulatory Commission. Explicit dynamic finite element models of full systems are increasingly common in industry for determining structural integrity during hypothetical drop accidents. Full cask and package model results are also used as the loading basis for single fuel pin impact models, which evaluate the response of fuel cladding under drop conditions. In this paper, a simplified package system is evaluated to illustrate several important structural dynamic phenomena, including the effect of gaps between components, the difference in local response at various points on a package during impact, and the effect of modeling various simplified representations of the basket and fuel assemblies. This paper focuses on the package impact analysis, and how loading conditions for a subsequent fuel assembly or fuel cladding analysis can be extracted.

Klymyshyn, Nicholas A.↗

NASA NTRS2003

Models Required to Mitigate Impacts of Space Weather on Space Systems

This viewgraph presentation attempts to develop a model of factors which need to be considered in the design and construction of spacecraft to lessen the effects of space weather on these vehicles. Topics considered include: space environments and effects, radiation environments and effects, space weather drivers, space weather models, climate models, solar proton activity and mission design for the GOES mission. The authors conclude that space environment models need to address issues from mission planning through operations and a program to develop and validate authoritative space environment models for application to spacecraft design does not exist at this time.

Barth, Janet L.↗

DOE OSTI2015

Climate Science Performance, Data and Productivity on Titan

Climate Science models are flagship codes for the largest of high performance computing (HPC) resources, both in visibility, with the newly launched Department of Energy (DOE) Accelerated Climate Model for Energy (ACME) effort, and in terms of significant fractions of system usage. The performance of the DOE ACME model is captured with application level timers and examined through a sizeable run archive. Performance and variability of compute, queue time and ancillary services are examined. As Climate Science advances in the use of HPC resources there has been an increase in the required human and data systems to achieve programs goals. A description of current workflow processes (hardware, software, human) and planned automation of the workflow, along with historical and projected data in motion and at rest data usage, are detailed. The combination of these two topics motivates a description of future systems requirements for DOE Climate Modeling efforts, focusing on the growth of data storage and network and disk bandwidth required to handle data at an acceptable rate.

Mayer, Benjamin W↗