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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 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
NASA NTRS2022

Validation of a High-Fidelity Supersonic Parachute Inflation Dynamics Model and Best Practice

The parachute inflation dynamics (PID) of a Disk-Gap-Band (DGB) parachute system travelling at supersonic velocities in the high-altitude Earth atmosphere is simulated using a high-fidelity, multiphysics, massively-parallel computational framework. The sensitivity of the simulation results with respect to critical modelling and simulation parameters, including the fluid mechanical governing equations (Euler vs Navier-Stokes with RANS turbulence closure vs Navier-Stokes with LES turbulence closer), the interaction between the flow and the suspension lines (accounted for vs not accounted for), the dynamics of the payload (restrained vs free), and the material model of the heterogeneous fabric canopy (Saint-Venant Kirchoff vs mechanics-informed multiscale neural network), is extensively investigated. The parameter investigation is enabled by advancements to the state-of-the-art in the modelling and simulation of the supersonic parachute inflation process, which are presented as part of the computational framework. The predictive quality of the computational framework in the context of supersonic PID is validated by comparison of the simulation results with the experimental results from NASA’s Advanced Supersonic Parachute Research (ASPIRE) project. Through the validation, best practices for the modelling and simulation of supersonic PID are developed and proposed.

Rabinovitch, Jason↗
DOE OSTI2024

Area V: Waste Management and Subsurface Science (FY21-23 Final Report)

The objective of the Waste Management and Subsurface Science Topic Area V project is to evaluate the feasibility and safety of an intermediate-depth borehole for disposal of Israel Atomic Energy Commission (IAEC) nuclear waste. The IAEC nuclear waste is currently stored in above ground and/or in near-surface facilities that provide short-term radiological worker safety but do not provide long-term, full security and safeguards protection for the nuclear material. Disposal of the IAEC nuclear waste several hundred meters below the surface in a sealed borehole would provide long-term security and safeguards due to its depth underground, as well as long-term radiological safety, due to its isolation in a stable geological formation. This project supports the nuclear security and safeguards initiatives of the Science and Technology Working Group of the NNSA/IAEC Memorandum of Understanding (MOU) and addresses the Topic Area V objective and associated goals. The goals for Topic Area V are: (1) Assess the suitability of the vadose zone in the Yamin Plain of the northern Negev Desert, Israel as a host location for intermediate-depth borehole disposal of radioactive waste, (2) Define and refine the necessary characterization needs to better understand the regional climate, structure, and stratigraphy, geomechanics, geochemistry, hydrogeology, and seismicity of the stratigraphic sequence from the surface to the water table in the vicinity of the proposed host location for the disposal borehole(s), and (3) Develop a preliminary plan and schedule, including necessary resources and costs, for a borehole disposal concept and robust and transparent pre-closure and post-closure safety assessments. The safety assessments will require iteration with process level models at both site and regional scales. Upon completion, the information collected by this effort will allow the IAEC to make decisions regarding the viability and applicability of an intermediate depth (<500m) borehole for disposal in the vadose zone of the Yamin Plain. This FY21-23 final report is provided in lieu of a workshop report that was originally planned for delivery in January, 2024. Due to the conflict in Israel and associated delays, the workshop has been delayed to April 2024. The workshop will be held at LLNL but offsite and will switch to hybrid if travel restrictions remain in place. The associated workshop report will be provided as part of a new FY24-26 LCP.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1980

The diffuse X-ray background spectrum from 3 to 50 keV

The spectrum of the extragalactic diffuse X-ray background has been measured with the GSFC Cosmic X-ray Experiment on HEAO 1 for regions of the sky away from known point sources and more than 20 deg from the galactic plane. A total exposure of 80 sq m-s-sr is available at present. Free-free emission from an optically thin plasma of 40 plus or minus 5 keV provides an excellent description of the observed spectrum from 3 to 50 keV. This spectral shape is confirmed by measurements from five separate layers of three independent detectors. With an estimated absolute precision of about 10%, the intensity of the emission at 10keV is 3.2 keV/keV/sq cm/s/sr, a value consistent with the average of previously reported spectra. A uniform hot intergalactic medium of approximately 36% of the closure density of the universe would produce such a flux, although nonuniform models indicating less total matter are probably more realistic.

Marshall, F. E.↗
NASA NTRS1979

Supersonic viscous flow over cones at incidence

The conically symmetric Navier-Stokes equations are solved by MacCormack's method for the supersonic flow past sharp cones at incidence. To provide closure for the case of turbulent flows, a scalar eddy-viscosity model based on mixing length hypotheses is used. The results are compared with available experimental data.

Mcrae, D. S.↗
NASA NTRS1991

Calculations of particle-laden flows by second-moment closures

A differential second-moment closure is applied to calculate nonswirling turbulent particle-laden jet flow. The closure is effected by extending constant-density single-phase turbulence models to the continuous (carrier) phase of two-phase flow. The dispersed (discrete) phase is treated by stochastic-Lagrangian technique. To reduce the effects of numerical (false) diffusion on the predicted results, a higher order differencing scheme, namely the flux-spline, is employed. In addition, an experimental study is conducted to provide data of good quality, especially near the inlet, for model assessment. The experiment consists of a confined coaxial jet flow of air with glass beads. The beads' diameter is 105 microns and is injected from the inner jet with a mass loading ratio of 0.9. The computed results are in good agreement with experimental data, especially for the carrier phase. However, the predicted turbulence fluctuations associated with the discrete phase are lower than the data at the downstream region of the flow field.

Nikjooy, M.↗
NASA NTRS1991

Stationary turbulent closure via the Hopf functional equation

Explicit solutions of the stationary Hopf equation are discussed and their computational possibilities are explored. The motivation is to circumvent the infinite hierarchy of coupled equations for the velocity moments and obtain an exact closure of the steady-state 3D Navier-Stokes equations, without modeling assumptions or truncation. The Hopf formulation of the Navier-Stokes equation is reviewed. A stationary homogeneous solution for 2D flow is displayed and discussed. It is shown how depletion of nonlinearity may arise for 3D forced homogeneous flow. The general 3D forced case is considered and a method for closing the 3D unforced equations with arbitrary boundary conditions is derived.

Shen, Hubert H.↗
NASA NTRS1994

The coupling between flame surface dynamics and species mass conservation in premixed turbulent combustion

Current flamelot models based on a description of the flame surface dynamics require the closure of two inter-related equations: a transport equation for the mean reaction progress variable, (tilde)c, and a transport equation for the flame surface density, Sigma. The coupling between these two equations is investigated using direct numerical simulations (DNS) with emphasis on the correlation between the turbulent fluxes of (tilde)c, bar(pu''c''), and Sigma, (u'')(sub S)Sigma. Two different DNS databases are used in the present work: a database developed at CTR by A. Trouve and a database developed by C. J. Rutland using a different code. Both databases correspond to statistically one-dimensional premixed flames in isotropic turbulent flow. The run parameters, however, are significantly different, and the two databases correspond to different combustion regimes. It is found that in all simulated flames, the correlation between bar(pu''c'') and (u'')(sub S)Sigma is always strong. The sign, however, of the turbulent flux of (tilde)c or Sigma with respect to the mean gradients, delta(tilde)c/delta(x) or delta(Sigma)/delta(x), is case-dependent. The CTR database is found to exhibit gradient turbulent transport of (tilde)c and Sigma, whereas the Rutland DNS features counter-gradient diffusion. The two databases are analyzed and compared using various tools (a local analysis of the flow field near the flame, a classical analysis of the conservation equation for (tilde)(u''c''), and a thin flame theoretical analysis). A mechanism is then proposed to explain the discrepancies between the two databases and a preliminary simple criterion is derived to predict the occurrence of gradient/counter-gradient turbulent diffusion.

Trouve, A.↗
NASA NTRS1994

Bioregenerative life-support systems

Long-duration future habitation of space involving great distances from Earth and/or large crew sizes (eg, lunar outpost, Mars base) will require a controlled ecological life-support system (CELSS) to simultaneously revitalize atmosphere (liberate oxygen and fix carbon dioxide), purify water (via transpiration), and generate human food (for a vegetarian diet). Photosynthetic higher plants and algae will provide the essential functions of biomass productivity in a CELSS, and a combination of physicochemical and bioregenerative processes will be used to regenerate renewable resources from waste materials. Crop selection criteria for a CELSS include nutritional use characteristics as well as horticultural characteristics. Cereals, legumes, and oilseed crops are used to provide the major macronutrients for the CELSS diet. A National Aeronautics and Space Administration (NASA) Specialized Center of Research and Training (NSCORT) was established at Purdue University to establish proof of the concept of the sustainability of a CELSS. The Biosphere 2 project in Arizona is providing a model for predicted and unpredicted situations that arise as a result of closure in a complex natural ecosystem.

NASA Discipline Life Support Systems↗
NASA NTRS2008

Deflection Analysis of the Space Shuttle External Tank Door Drive Mechanism

Upon observing an abnormal closure of the Space Shuttle s External Tank Doors (ETD), a dynamic model was created in MSC/ADAMS to conduct deflection analyses of the Door Drive Mechanism (DDM). For a similar analysis, the traditional approach would be to construct a full finite element model of the mechanism. The purpose of this paper is to describe an alternative approach that models the flexibility of the DDM using a lumped parameter approximation to capture the compliance of individual parts within the drive linkage. This approach allows for rapid construction of a dynamic model in a time-critical setting, while still retaining the appropriate equivalent stiffness of each linkage component. As a validation of these equivalent stiffnesses, finite element analysis (FEA) was used to iteratively update the model towards convergence. Following this analysis, deflections recovered from the dynamic model can be used to calculate stress and classify each component s deformation as either elastic or plastic. Based on the modeling assumptions used in this analysis and the maximum input forcing condition, two components in the DDM show a factor of safety less than or equal to 0.5. However, to accurately evaluate the induced stresses, additional mechanism rigging information would be necessary to characterize the input forcing conditions. This information would also allow for the classification of stresses as either elastic or plastic.

Tosto, Michael A.↗
NASA NTRS2018

VCCT with Progressive Nodal Release for Simulating Mixed-Mode Delamination: Formulation, Algorithmic Improvements and Implications

To simulate the propagation of cracks using the Virtual Crack Closure Technique (VCCT), intermediate crack positions between existing node pairs can be modeled by progressively releasing the nodes using fracture mechanics principles. This approach has been implemented in commercial software and can be applied to simulate delamination growth. Recent research has provided insight into the synchronized mixed mode nodal release, extending and formalizing the methodology for delamination growth. This paper documents the development of the Jacobians associated with delamination propagation under quasi-static mixed-mode conditions, leading to improvements in convergence of the implicit nonlinear solvers used.

Mabson, G. E.↗
NASA NTRS2018

VCCT with Progressive Nodal Release for Simulating Mixed-Mode Delamination: Formulation, Algorithmic Improvements and Implications

To simulate the propagation of cracks using the Virtual Crack Closure Technique (VCCT), intermediate crack positions between existing node pairs can be modeled by progressively releasing the nodes using fracture mechanics principles. This approach has been implemented in commercial software and can be applied to simulate delamination growth. Recent research has provided insight into the synchronized mixed mode nodal release, extending and formalizing the methodology for delamination growth. This paper documents the development of the Jacobians associated with delamination propagation under quasi-static mixed-mode conditions, leading to improvements in convergence of the implicit nonlinear solvers used.

G E Mabson↗
NASA NTRSDate not supplied

Interlaminar R-Curve Effects in Thermoplastic Composites: Experiments and Model Correlations

The interlaminar fracture behavior of thermoplastic composites under Mode-I and Mode-II static loading is investigated in this research. The material system under consideration is a carbon fiber reinforced low melt semi-crystalline resin TC1225 LMPAEK T700G (T700/LMPAEK)†. Characterization experiments were conducted to measure the load-displacement response, peak load, and propagation of delamination from a pre-implanted Kapton® insert. The Mode-I response was characterized using a double cantilever beam (DCB) test according to the ASTM D5528-22 standard. It was observed that the propagation exhibited significant resistance to delamination growth, i.e., an R-Curve effect. The test data indicated that the steady-state fracture toughness, G SS I , was approximately twice the mean initiation fracture toughness, G Ic . The Mode-II response of an end notch flexure (ENF) specimen tested according to the ASTM D7905-19 standard exhibited an unexpected stable behavior upon attaining peak load. Prior to attaining peak load, the Mode-II response exhibited some non-linearity, which may be attributed to nonlinear bulk material response, e.g., hyper-elasticity, viscoelasticity, plasticity, etc., and potentially friction at the load/support rollers and R-Curve effects. Finite element models based on the Cohesive Zone Method (CZM) and the Virtual Crack Closure Technique (VCCT) were used to predict the DCB and ENF specimen responses. DCB analysis results obtained using G SS I predicted propagation consistent with experimental data. However, results obtained with the as characterized G Ic were inaccurate in predicting delamination growth onset and peak load. ENF analysis results obtained with the as-characterized Mode-II fracture toughness, G IIc , were inaccurate in predicting the peak load and propagation. Hence, R-Curve effects were included in both DCB and ENF simulations, which enabled improved predictions. The experimentally determined Mode-I R-Curve was used for the DCB simulations, whereas an R-Curve was derived for Mode-II assuming that the change in compliance of the specimen was associated with crack growth only.

Prabhakar M Rao↗
NASA NTRSDate not supplied

Interlaminar R-Curve Effects in Thermoplastic Composites: Experiments and Model Correlations

The interlaminar fracture behavior of thermoplastic composites under Mode-I and Mode-II static loading is investigated in this research. The material system under consideration is a carbon fiber reinforced low melt semi-crystalline resin TC1225 LMPAEK T700G (T700/LMPAEK)†. Characterization experiments were conducted to measure the load-displacement response, peak load, and propagation of delamination from a pre-implanted Kapton® insert. The Mode-I response was characterized using a double cantilever beam (DCB) test according to the ASTM D5528-22 standard. It was observed that the propagation exhibited significant resistance to delamination growth, i.e., an R-Curve effect. The test data indicated that the steady-state fracture toughness, G SS I , was approximately twice the mean initiation fracture toughness, G Ic . The Mode-II response of an end notch flexure (ENF) specimen tested according to the ASTM D7905-19 standard exhibited an unexpected stable behavior upon attaining peak load. Prior to attaining peak load, the Mode-II response exhibited some non-linearity, which may be attributed to nonlinear bulk material response, e.g., hyper-elasticity, viscoelasticity, plasticity, etc., and potentially friction at the load/support rollers and R-Curve effects. Finite element models based on the Cohesive Zone Method (CZM) and the Virtual Crack Closure Technique (VCCT) were used to predict the DCB and ENF specimen responses. DCB analysis results obtained using G SS I predicted propagation consistent with experimental data. However, results obtained with the as characterized G Ic were inaccurate in predicting delamination growth onset and peak load. ENF analysis results obtained with the as-characterized Mode-II fracture toughness, G IIc , were inaccurate in predicting the peak load and propagation. Hence, R-Curve effects were included in both DCB and ENF simulations, which enabled improved predictions. The experimentally determined Mode-I R-Curve was used for the DCB simulations, whereas an R-Curve was derived for Mode-II assuming that the change in compliance of the specimen was associated with crack growth only.

Prabhakar Rao↗
NASA NTRS2000

Diurnal Variability of the Hydrologic Cycle and Radiative Fluxes: Comparisons Between Observation and a GCM

The simulated diurnal cycle is in many ways an ideal test bed for new physical parameterizations. The purpose of this paper is to compare observations from the Tropical Rainfall Measurement Mission, the Earth Radiation Budget Experiment, the International Satellite Cloud Climatology Project, the Clouds and the Earth's Radiant Energy System Experiment, and the Anglo-Brazilian Amazonian Climate Observation Study with the diurnal variability of the Amazonian hydrologic cycle and radiative energy budget as simulated by the Colorado State University general circulation model, and to evaluate improvements and deficiencies of the model physics. The model uses a prognostic cumulus kinetic energy (CKE) to relax the quasi-equilibrium closure of the Arakawa-Schubert cumulus parameterization. A parameter, alpha, is used to relate the CKE to the cumulus mass flux. This parameter is expected to vary with cloud depth, mean shear, and the level of convective activity, but up to now a single constant value for all cloud types has been used. The results of the present study show clearly that this approach cannot yield realistic simulations of both the diurnal cycle and the monthly mean climate state. Improved results are obtained using a version of the model in which alpha is permitted to vary with cloud depth.

Lin, Xin↗
NASA NTRS2022

Analysis of the MODIS Above-Cloud Aerosol Retrieval Algorithm Using MCARS

The Multi-sensor Cloud and Aerosol Retrieval Simulator (MCARS) presently produces synthetic radiance data from Goddard Earth Observing System version 5 (GEOS-5) model output as if the Moderate Resolution Imaging Spectroradiometer (MODIS) was viewing a combination of atmospheric column inclusive of clouds, aerosols and a variety of gases and land/ocean surface at a specific location. In this paper we use MCARS to study the MODIS Above-Cloud AEROsol retrieval algorithm (MOD06ACAERO). MOD06ACAERO is presently a regional research algorithm able to retrieve aerosol optical thickness over clouds, in particular absorbing biomass burning aerosols overlying marine boundary layer clouds in the Southeastern Atlantic Ocean. The algorithm’s ability to provide aerosol information in cloudy conditions makes it a valuable source of information for modeling and climate studies n an area where current clear sky-only operational MODIS aerosol retrievals effectively have a data gap between the months of June and October. We use MCARS for a verification and closure study of the MOD06ACAERO algorithm. The purpose of this study is to develop a set of constraints a model developer might use during assimilation of MOD06ACAERO data. Our simulations indicate that the MOD06ACAERO algorithm performs well for marine boundary layer clouds in the SE Atlantic provided some specific screening rules are observed. For the present study, a combination of five simulated MODIS data granules was used for a dataset of 13.5 million samples with known input conditions. When pixel retrieval uncertainty was less than 30%, optical thickness of the underlying cloud layer was greater than 4 and scattering angle range within the cloud bow was excluded, MOD06ACAERO retrievals agreed with the underlying ground truth (GEOS-5 cloud and aerosol profiles used to generate the synthetic radiances) with a slope of 0.913, offset of 0.06, and RMSE=0.107. When only near-nadir pixels were considered (view zenith angle within +/-20 degrees) the agreement with source data further improved (0.977, 0.051 and 0.096 respectively). Algorithm closure was examined using a single case out of the five 38 used for verification. For closure, the MOD06ACAERO code was modified to use GEOS-5 temperature and moisture profiles as ancillary. Agreement of MOD06ACAERO retrievals with source data for the closure study had a slope of 0.996 with offset -0.007 and RMSE of 0.097 at pixel uncertainty level of less than 40%, illustrating the benefits of high-quality ancillary atmospheric data for such retrievals.

MODIS↗
DOE OSTI2020

Evaluating and Improving Convective Parameterization for GCMs Using ARM Observations. Final report

This technical report summarizes the achievements during the project period funded by the Atmospheric System Research (ASR) program. The general goal of the project is to improve the representation of atmospheric deep convection in global climate models. By using DOE Atmospheric Radiation Measurement (ARM) program observations and a hierarchy of models from cloud-resolving to global climate models, we evaluated and improved many aspects of convection parameterization schemes, such as the trigger function for convection and closure condition to determine the amount of convection. We also incorporated the stochasticity of convection into a convection scheme. These improvements, when implemented into the National Center for Atmospheric Research (NCAR) Community Earth System Model (CESM) and the DOE Exascale Energy Earth System Model (E3SM), led to improved simulation of precipitation characteristics, including precipitation intensity, Intertropical Convergence Zone, and Madden-Julian oscillation. The project also improved the representation of microphysical processes in convective clouds. It enables the interaction of cloud microphysics with aerosols in weather and climate models.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Experiment-modeling studies comparing energy dissipation in the DIII-D SAS and SAS-VW divertors

Recent DIII-D experiments on Small Angle Slot (SAS) divertors have confirmed that a combination of divertor closure and target shaping can enhance cooling across the divertor target and increase energy dissipation, but with significant dependence on B T (toroidal magnetic field) direction. In these novel divertors, the roles of closure, target shaping, drifts, and scale lengths are all interconnected in optimizing dissipation, with the separatrix electron density n eSEP being the key parameter associated with the level of dissipation/detachment. After modifying the original flat-targeted graphite SAS to include a V shape with a tungsten coating on the outer side of the divertor (SAS-VW), matched series of discharges were run to compare to detailed SOLPS-ITER modeling. Experimentally, when run as designed with the outer strike point at the slot vertex, SAS-VW requires nearly identical n eSEP for detachment as the original SAS, with little difference in dissipation for the new geometry. This is in contrast to (1) earlier modeling predictions that a small change of the SAS geometry to a V shape should enhance dissipation at the same n eSEP for magnetic configurations having better H-mode access (ion B × ∇B drift directed into the divertor), and (2) despite the achievement of significantly higher (2-7x) neutral pressures and compression in the SAS-VW slot. Comparisons of experimental density scans to the most recent SOLPS-ITER modeling with ExB drifts show reasonable agreement for dissipation/detachment onset when using separatrix density as the independent parameter. In order to help understand the discrepancy in modeled vs actual performance for the new configuration, additional measurements varying gas injection location and impurity injection were undertaken. In-slot D 2 gas fueling is more effective (5–22 %) in promoting detachment, in accord with modeling. In-slot impurity injection (N 2 or Ne) can yield 30 % lower core Z eff and 15 % less confinement degradation after detachment compared to main chamber puffing, as well as relatively lower tungsten leakage from the divertor. Modeling can also reproduce the improved detachment seen as the strike point moves inboard of the slot vertex. While we can explain the effects of the most important parameters causing energy dissipation in these slot divertors, it remains that many aspects of their behavior cannot be accurately modeled using state-of-art codes such as SOLPS-ITER. This is of concern for future model-driven designs utilizing similar V-shaped geometries.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

A dehydrated, aseptically-processed human amnion/chorion allograft accelerates healing in a delayed murine excisional wound model

Since chronic, non-healing wounds represent an increasing source of economic and temporal burden for patients who suffer from them and healthcare professionals that treat them, therapeutic modalities that promote closure of delayed and non-healing wounds are of utmost importance. Recent clinical results of allografts derived from amnion and chorion placental layers encourage further investigation of the mechanisms underlying clinical efficacy of these products for treatment of wounds. Here, we utilized a diabetic murine splinted excisional wound model to investigate the effects of a dehydrated human amnion/chorion-derived allograft (dHACA) on delayed wound healing, as well as the effects of dehydrated allograft derived solely from amnion tissue of the same donor. We examined wound healing by histological endpoint analysis, and we assessed other parameters relevant to functional wound healing in the wound bed including angiogenesis, macrophage phenotypes, proliferative activity, and gene expression. Herein we demonstrate that application of dHACA to a murine diabetic model of delayed wound progression results in better macroscale wound resolution outcomes, including rate of closure, compared to unaided wound progression, while dehydrated human amnion allograft (dHAA) fails to improve outcomes. Improved gross wound resolution observed with dHACA was accompanied by increased granulation tissue formation, proliferation and vascular ingrowth observed in the wound bed, early macrophage polarization towards anti-inflammatory phenotypes, and downregulation of pro-fibrotic gene expression. Overall, our data suggest that improvements in the rates of delayed wound closure observed from combined amnion/chorion allografts are associated with modulation of critical cellular and tissue processes commonly found to be dysregulated in delayed healing wounds, including proliferation, vascularization, inflammation, and re-epithelialization.

60 APPLIED LIFE SCIENCES↗