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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS2013

Floating Node Method and Virtual Crack Closure Technique for Modeling Matrix Cracking-Delamination Migration

A novel approach is proposed for high-fidelity modeling of progressive damage and failure in composite materials that combines the Floating Node Method (FNM) and the Virtual Crack Closure Technique (VCCT) to represent multiple interacting failure mechanisms in a mesh-independent fashion. In this study, the approach is applied to the modeling of delamination migration in cross-ply tape laminates. Delamination, matrix cracking, and migration are all modeled using fracture mechanics based failure and migration criteria. The methodology proposed shows very good qualitative and quantitative agreement with experiments.

DeCarvalho, Nelson V.↗
NASA NTRS2014

Assessment of Higher-Order RANS Closures in a Decelerated Planar Wall-Bounded Turbulent Flow

A reference DNS database is presented, which includes third- and fourth-order moment budgets for unstrained and strained planar channel flow. Existing RANS closure models for third- and fourth-order terms are surveyed, and new model ideas are introduced. The various models are then compared with the DNS data term by term using a priori testing of the higher-order budgets of turbulence transport, velocity-pressure-gradient, and dissipation for both the unstrained and strained databases. Generally, the models for the velocity-pressure-gradient terms are most in need of improvement.

Jeyapaul, Elbert↗
NASA NTRS2016

Advanced Technologies to Improve Closure of Life Support Systems

As NASA looks beyond the International Space Station toward long-duration, deep space missions away from Earth, the current practice of supplying consumables and spares will not be practical nor affordable. New approaches are sought for life support and habitation systems that will reduce dependency on Earth and increase mission sustainability. To reduce launch mass, further closure of Environmental Control and Life Support Systems (ECLSS) beyond the current capability of the ISS will be required. Areas of particular interest include achieving higher degrees of recycling within Atmosphere Revitalization, Water Recovery and Waste Management Systems. NASA is currently investigating advanced carbon dioxide reduction processes that surpass the level of oxygen recovery available from the Sabatier Carbon Dioxide Reduction Assembly (CRA) on the ISS. Candidate technologies will potentially improve the recovery of oxygen from about 50% (for the CRA) to as much as 100% for technologies who's end product is solid carbon. Improving the efficiency of water recycling and recovery can be achieved by the addition of advanced technologies to recover water from brines and solid wastes. Bioregenerative technologies may be utilized for water reclaimation and also for the production of food. Use of higher plants will simultaneously benefit atmosphere revitalization and water recovery through photosynthesis and transpiration. The level at which bioregenerative technologies are utilized will depend on their comparative requirements for spacecraft resources including mass, power, volume, heat rejection, crew time and reliability. Planetary protection requirements will need to be considered for missions to other solar system bodies.

Barta, Daniel J.↗
NASA NTRS2015

Cloud Feedbacks on Greenhouse Warming in a Multi-Scale Modeling Framework with a Higher-Order Turbulence Closure

Five-year simulation experiments with a multi-scale modeling Framework (MMF) with a advanced intermediately prognostic higher-order turbulence closure (IPHOC) in its cloud resolving model (CRM) component, also known as SPCAM-IPHOC (super parameterized Community Atmospheric Model), are performed to understand the fast tropical (30S-30N) cloud response to an instantaneous doubling of CO2 concentration with SST held fixed at present-day values. SPCAM-IPHOC has substantially improved the low-level representation compared with SPCAM. It is expected that the cloud responses to greenhouse warming in SPCAM-IPHOC is more realistic. The change of rising motion, surface precipitation, cloud cover, and shortwave and longwave cloud radiative forcing in SPCAM-IPHOC from the greenhouse warming will be presented in the presentation.

Cheng, Anning↗
NASA NTRS2015

How Difficult is it to Reduce Low-Level Cloud Biases With the Higher-Order Turbulence Closure Approach in Climate Models?

Low-level clouds cover nearly half of the Earth and play a critical role in regulating the energy and hydrological cycle. Despite the fact that a great effort has been put to advance the modeling and observational capability in recent years, low-level clouds remains one of the largest uncertainties in the projection of future climate change. Low-level cloud feedbacks dominate the uncertainty in the total cloud feedback in climate sensitivity and projection studies. These clouds are notoriously difficult to simulate in climate models due to its complicated interactions with aerosols, cloud microphysics, boundary-layer turbulence and cloud dynamics. The biases in both low cloud coverage/water content and cloud radiative effects (CREs) remain large. A simultaneous reduction in both cloud and CRE biases remains elusive. This presentation first reviews the effort of implementing the higher-order turbulence closure (HOC) approach to representing subgrid-scale turbulence and low-level cloud processes in climate models. There are two HOCs that have been implemented in climate models. They differ in how many three-order moments are used. The CLUBB are implemented in both CAM5 and GDFL models, which are compared with IPHOC that is implemented in CAM5 by our group. IPHOC uses three third-order moments while CLUBB only uses one third-order moment while both use a joint double-Gaussian distribution to represent the subgrid-scale variability. Despite that HOC is more physically consistent and produces more realistic low-cloud geographic distributions and transitions between cumulus and stratocumulus regimes, GCMs with traditional cloud parameterizations outperform in CREs because tuning of this type of models is more extensively performed than those with HOCs. We perform several tuning experiments with CAM5 implemented with IPHOC in an attempt to produce the nearly balanced global radiative budgets without deteriorating the low-cloud simulation. One of the issues in CAM5-IPHOC is that cloud water content is much higher than in CAM5, which is combined with higher low-cloud coverage to produce larger shortwave CREs in some low-cloud prevailing regions. Thus, the cloud-radiative feedbacks are exaggerated there. The turning exercise is focused on microphysical parameters, which are also commonly used for tuning in climate models. The results will be discussed in this presentation.

Xu, Kuan-Man↗
NASA NTRS2016

Modeling Fatigue Damage Onset and Progression in Composites Using an Element-Based Virtual Crack Closure Technique Combined With the Floating Node Method

A new methodology is proposed to model the onset and propagation of matrix cracks and delaminations in carbon-epoxy composites subject to fatigue loading. An extended interface element, based on the Floating Node Method, is developed to represent delaminations and matrix cracks explicitly in a mesh independent fashion. Crack propagation is determined using an element-based Virtual Crack Closure Technique approach to determine mixed-mode energy release rates, and the Paris-Law relationship to obtain crack growth rate. Crack onset is determined using a stressbased onset criterion coupled with a stress vs. cycle curve and Palmgren-Miner rule to account for fatigue damage accumulation. The approach is implemented in Abaqus/Standard® via the user subroutine functionality. Verification exercises are performed to assess the accuracy and correct implementation of the approach. Finally, it was demonstrated that this approach captured the differences in failure morphology in fatigue for two laminates of identical stiffness, but with layups containing θdeg plies that were either stacked in a single group, or distributed through the laminate thickness.

De Carvalho, Nelson V.↗
NASA NTRS2018

Combining Progressive Nodal Release with the Virtual Crack Closure Technique to Model Fatigue Delamination Growth Without Re-Meshing

The present work summarizes an approach to model mixed-mode 3D fatigue crack growth using the Virtual Crack Closure Technique (VCCT) without requiring re-meshing. It is demonstrated that the proposed approach can be used to simulate crack shapes that do not conform to the underlying mesh. The proposed approach relies solely on Paris Law characterization data to model delamination growth. Growth is determined as a post-processing step at the end of each increment, and hence no convergence issues associated with the progressive nodal release are encountered. This approach can be readily applied using standard solid element formulations and is implemented via an interface user element in Abaqus/Standard.

Carvalho, N. V. De↗
NASA NTRS2019

A New Approach to Model Delamination Growth in Fatigue Using the Virtual Crack Closure Technique Without Re-Meshing

A modeling approach is proposed to simulate delamination propagation in fatigue that combines the Virtual Crack Closure Technique (VCCT) with a progressive nodal release strategy. The progressive nodal release alleviates the artificial stress concentrations found when using the VCCT with instantaneous release to model 3D delamination without re-meshing. This enables crack shapes that do not conform to the underlying mesh to be readily simulated. The progressive release is formulated such that no artificial growth or healing occurs as a result of a change in loading conditions. Furthermore, expressions for calculating energy release rates at partially released nodes are proposed and applied to arbitrarily shaped delamination fronts. The shape of the delamination front is considered explicitly in the energy release rate calculations, and is determined by considering the normalized crack positions associated with the partial nodal release. Contrary to previous implementations, the local delamination propagation direction is not assumed to follow mesh lines, but instead is computed as part of the iterative procedure proposed to determine the maximum energy release along the crack front. The results obtained suggest the approach can accurately simulate Mode I, Mixed Mode I/II and Mode II fatigue delamination growth and be used to simulate growth of arbitrarily shaped cracks that do not conform to the underlying mesh.

N V De Carvalho↗
NASA NTRSDate not supplied

Modeling Pore Closure in the Hot Isostatic Pressing of Additively Manufactured Inconel 718 Samples

Additive manufacturing provides opportunity for a new world of possibilities for metallic component design and fabrication; however, as-built part quality is notoriously variable, anisotropic, and degraded by porous defects. To improve quality, parts are commonly post processed using a variety of techniques including hot isostatic pressing (HIP). During HIP, high temperature and pressure is employed to improve microstructure and reduce pore volume by inducing visco-plastic deformation in the metallic substrate. Validated computational capabilities can provide predictions to guide the selection of processing condition, expected pore reduction, and the effects of varying entrapped gas in the pores. This discussion describes a micro-scale finite element structural model developed to predict pore closure due to HIP in as-built additively manufactured Inconel 718 samples produced by the laser powder bed fusion process. The model accounts for plastic deformation, creep, and internal pressure for a single pore. Pores are characterized in physical samples before and after HIP, and model predictions are compared to this measured data.

defect model prediction↗
NASA NTRS2024

Discounting Water for Optimal Carbon Gain as a Basis of Stomatal Closure

The exchange of carbon dioxide and water vapor between terrestrial ecosystems and the atmosphere is regulated by stomata (small pores in the leaves of plants). Unsurprisingly, environmental factors controlling the opening and closure of stomata has been sought as early as 1800. One approach, popularized in the early 1970s, is a stomatal optimization framework. This framework is based on the hypothesis that plants optimize carbon gain subject to water loss or water availability constraints. This constraint optimization problem was solved in various forms assuming instantaneous adjustments of stomatal aperture to maximize a reward function with no future foresight or legacy effects. Holtzman et al. (2024, https://doi.org/10.1029/2023av001113) offers a novel approach that can diagnose the effective timescale over which the reward function maximization must be time-integrated. The developed method thus optimizes an integrated carbon gain function but adjusted by a discount factor subject to water availability in the root zone. The discount factor considers how the plant values carbon gain to save water and its timescale can be inferred from observations because the model is analytically tractable. The results suggest that the most important climate factor that determines this discount timescale is multi-annual mean of the longest dry period during the growing season. The findings highlight how local climate traits influence the spatial variation in ecosystem-level water use strategies. This sets the stage for expanding such a framework to cases where multiple constraints act in concert while operating at distinct time scales.

stomata↗
DOE OSTI2017

Validation of CTF Droplet Entrainment and Annular/Mist Closure Models using Riso Steam/Water Experiments

This document summarizes the work to validate the droplet entrainment and de-entrainment models, as well as two-phase closure models in the CTF code [1] by comparison with experimental data obtained at Risø National Laboratory [2]. CTF is the modernized version of the subchannel code, COBRA-TF [3], being jointly developed by Oak Ridge National Laboratory and North Carolina State University for applications in the Consortium for Advanced Simulation of Light Water Reactors (CASL). The Risø data included a series of more than 250 steam/water experiments that were performed in both tube and annulus geometries over a range of various pressures and outlet qualities. Experimental conditions wereset so that the majority of cases were in the annular/mist flow regime. Measurements included liquid film flow rate, droplet flow rate, film thickness, and two-phase pressure drop. CTF was used to model 180 of the tubular geometry cases, matching experimental geometry, outlet pressure, and outlet flow quality to experimental values. CTF results were compared to the experimental data at the outlet of the test section in terms of vapor flow fractions, and entrained liquid flow fractions, and pressure drop per unit length.

Wysocki, Aaron↗
DOE OSTI2019

Assessment of Enthalpy-Based Conditional Moment Closure Models in Predicting Ignition of Lean and Stoichiometric PRF-Air Mixtures with Temperature Inhomogeneity

Accurate prediction of the ignition delay in turbulent flows is important in developing advanced combustion technology for internal combustion engines. Enthalpy-based conditional moment closure (CMC) models are assessed with 2-D direct numerical simulation (DNS) data for ignition of homogeneous PRF-air mixtures with temperature inhomogeneity in homogeneous isotropic turbulence. The sensible-enthalpy-based CMC model is compared with the total-enthalpy-based formulation, with the focus being placed on assessing the capability of the CMC models in predicting ignition processes under different engine conditions. A priori analysis shows that the total-enthalpy-based CMC gives good predictions of the heat release rates in the lean mixtures when the temperature inhomogeneity level is low, but leads to significant overprediction under the stoichiometric condition regardless of the thermal stratification levels. On the other hand, the sensible enthalpy formulation performs well for all conditions considered in this study due to the suppressed conditional temperature fluctuations. A mapping method to model conditional scalar dissipation rates and probability density function of sensible enthalpy is also assessed.

Wang, Wei↗
DOE OSTI2020

Deformable closure mechanism

A deformable closure mechanism for an aperture that may include an aperture seal that has a seal seat between an internal support structure and an external support structure. A barrier structure may be configured to resealably close the aperture, and have a central membrane and a barrier sealed that is inflatable in order to engage the barrier structure with the aperture seal.

Doggett, William R.↗
DOE OSTI2022

DOESC Closure Leak Test Assembly

This conceptual design report is for the DOESC Closure Leak Test Assembly, which satisfies a portion of the milestone "Preliminary Design Report for Remote Helium Leak Test System". This CDR is part of the Preliminary Design Report/Package.

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DOE OSTI2017

Technology Basis for Savannah River Tank Closure Cesium Removal Project - 17448

Westinghouse is currently executing a contract, awarded in June 2016 from Savannah River Remediation LLC, to deliver a system capable of removing solids and up to 100,000 curies of Cesium-137 from tank 10H, located in the Savannah River 'tank farm'. Savannah River Remediation currently has the responsibility to perform work for the Savannah River Site Liquid Waste Operations Program at the Savannah River Site for the US government, represented by the US DOE under their Principal contract. The scope of work covers the detailed design, procurement, fabrication, and delivery of the system to the Savannah River Site. It also includes the factory acceptance testing of the system, prior to delivery to site. Before leaving the site, Westinghouse will perform an evaluation of the system assembly and operations training for the incumbent operator. The basis for the technology chosen to accomplish the solids and Cesium-137 removal is unique to the specific feed stream, but is based on well-known and successful technology, Toshiba SARRY water cleanup system. Toshiba is Westinghouse's parent company, allowing us to reach back and incorporate the lessons learned during the water cleanup at Fukushima Daiichi and the integration of various technologies. Another key to the technology basis was the ion exchange media selection. A number of possible ion exchange media for the cesium removal were considered with the final choice being inorganic CST resin. Several criteria were considered and compared, such as the radiation sensitivity of the CST and the cesium specific ion preference. This paper will present the conceptual design of the modular system, noting the key benefits of specific components in the overall technology basis. Along with the design, a look at key technology improvements carried into the design through the Toshiba SARRY system will be incorporated. A first feedback on the implementation of the overall project will be provided. Since this system is a first-of-a-kind in this specific application, interesting lessons learned will be provided for future tank closure activities. (authors)

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DOE OSTI2018

Remote Robotic Equipment for Retrieval of High Level Waste to Support Environmental Closure - 18162

The Idaho Cleanup Project contractor, Fluor Idaho, LLC, is responsible for managing HLW calcine stored in the Calcined Solids Storage Facility at the Idaho Nuclear Technology and Engineering Center. The Idaho Nuclear Technology and Engineering Center is a DOE managed facility located at the INL Site in the remote portions of southeast Idaho. In 2016, DOE directed Fluor Idaho to develop and test a full-scale retrieval system to demonstrate the ability to safely retrieve HLW calcine from the Calcined Solids Storage Facility for future retrieval and processing. Removing HLW calcine from the State of Idaho is required by the 1995 Settlement Agreement, which mandates that DOE have HLW calcine ready to be moved out of Idaho by December 2035. Fluor Idaho is currently testing retrieval and transfer concepts to ensure that the Calcined Solids Storage Facility is placed in a final configuration that is protective of human health and the environment after HLW calcine has been removed to the maximum extent practical. This paper describes the full-scale prototype that will be used to prove retrieval and transfer system design capabilities, verify operating parameters, and establish a basis for calcine retrieval efficacy. Additionally, it describes the retrieval (bulk and residual) and visual monitoring systems that were designed and tested in 2017 and will continue to be tested with the full-scale prototype. Testing (i.e., full-scale mockup, bulk retrieval, residual clean-out, and visualization monitoring) performed by Fluor Idaho will demonstrate the maximum extent practical of HLW calcine removal that is achievable. This is critical to (1) establish criteria for ending calcine removal activities, (2) evaluate cost and benefits associated with performing additional removal, and (3) ensure clean up and closure standards under applicable requirements (e.g., statutes, orders, and agreements) are met. (authors)

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DOE OSTI2018

Development of a Waste Management Organization for the Whiteshell Laboratories Closure Project - 18317

Whiteshell Laboratories (WL) has been generating and managing radioactive waste for over fifty years in support of a wide variety of research and operational applications. The current mission of the WL site, located in Manitoba, Canada, is to fully decommission the site to an approved end-state criterion and to disposition the waste in compliance with national and provincial regulations. To expedite the decommissioning schedule from over thirty years to nine years, which was a contractual commitment for the site operating company, Canadian Nuclear Laboratories (CNL), it became apparent that a centralized and optimized organization be established to coordinate all waste management activities and to fulfill the mission to process, condition, transport and disposition all radioactive wastes, which include Low-Level Waste (LLW), Intermediate-Level Waste (ILW) and High-Level Waste (HLW). The WL Waste Management Division was effectively established as a two-person operation in 2016 and has rapidly expanded to fulfill the mandate of managing nearly 30,000 cubic meters of LLW, ILW and HLW. This paper outlines the early lessons learned from managing important organizational changes without disrupting ongoing work practices; developing executive-level waste management strategies based on options studies and cost-benefit analysis comparisons; selection of storage vs. disposal disposition strategies; evaluation and selection of transportation methods and packages for LLW, ILW and HLW; and the need to develop an entire suite of programmatic documentation and procedures to support and instill a strong conduct of operations culture. The waste management strategy, which now focuses on transporting the waste to another province (Ontario) in a disposal ready form, represents the first large-scale radioactive waste transportation campaign in Canada that includes all three classes of waste. This paper provides additional insight on the overall waste management strategies for the WL Closure Project. (authors)

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DOE OSTI2019

Execution of an Alternative Modeling Strategy for Closure of the Rainier Mesa Corrective Action Unit at the Nevada National Security Site - 19099

The Underground Test Area (UGTA) Project of the U.S Department of Energy (DOE) is investigating radionuclide contaminant movements in groundwater derived from a decades-long period of underground nuclear testing at the Nevada National Security Site (NNSS) to support regulatory corrective action and closure requirements. The project is built around an integrated campaign of drilling and sampling, data interpretation, computer modeling, and broader monitoring activities conducted under a joint Federal Facilities Agreement and Consent Order (1996 as amended) (FFACO) between the State of Nevada, the DOE, and the U.S. Department of Defense. The FFACO strategy is applied to individual Corrective Action Units (CAUs) that roughly envelop disparate geographic testing areas at the NNSS. The Rainier Mesa/Shoshone Mountain (RMSM) CAU is a geologically and hydrologically complex system lying in a remote up-gradient section of the NNSS. It was the site of 67 underground tests conducted between 1957 and 1992, 61 at Rainier Mesa proper, and 6 at Shoshone Mountain, isolated to its south. The original strategy to close the RMSM CAU required a simulation-based investigation to define the evolution of contaminated volumes of groundwater (in 3D) under uncertainty as a means to define a surface-projected contaminant boundary and to serve as a basis for longer term monitoring activities. Early models developed under this strategy proved to be quite complex and difficult to calibrate. Additional costs required to better characterize the system were judged to be out of balance with the low risks associated with this particular CAU. As a result, an Alternative Modeling Strategy (AMS) was adopted. The AMS removes the requirement for developing ensembles of 3D simulations and replaces it with a simpler one requiring the generation of multiple 1D streamline models. These are meant to encompass a range of alternative, yet plausible release and transport scenarios as a means to bound the overall lateral extent of contaminant transport. This paper will review the modeling approach developed under the AMS and its application to the Rainier Mesa portion of the CAU. Preliminary model results made under different parametric assumptions and boundary condition scenarios will be presented. Additional refinements of the model and its further application will be discussed. (authors)

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