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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 1,693 records · Page 94
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Computational Fluid Dynamics-Based Modeling of Methane Flows Around Oil and Gas Equipment

Recent studies estimate that emissions from oil and gas production facilities contribute between 20 and 50% of the total methane ( CH 4 ) emitted in the US; therefore, quantifying and reducing these emissions are crucial for achieving climate goals. Methane quantification depends on both measuring methane concentrations and converting them to emissions through a modeling framework. Currently, simple atmospheric dispersion models are primarily used to quantify emissions and concentrations, but these estimates are highly uncertain when quantifying emissions from complex aerodynamic sources, such as oil and gas facilities. This investigation used a CFD modeling approach, which can account for aerodynamic complexity but has hitherto not been used to model methane concentrations downwind of a methane release of a known rate, and compared it against in situ measurements. High-time-resolution (1 Hz) methane concentration and meteorological data were measured during experiments conducted at the METEC on 21 March and 11 July 2024. The METEC site configuration, measured wind data, and controlled emission rates were used as input for the CONVERGE CFD model to model downwind CH 4 concentration. The modeling was carried out between 20 and 70 m, from two different points of release in two separate controlled-release experiments, one from a separator and another from a wellhead. In these experiments, we found that the CFD model could predict the CH 4 concentrations downwind of the release to a good degree. The model was evaluated on multiple metrics to assess its performance in estimating methane concentrations at typical fence line distances (∼30 m). These results help us to understand external flows and the ability of CFD models to predict downwind concentrations in aerodynamically complex environments.

03 NATURAL GAS↗
DOE OSTI2017

Estimating Jupiter’s Gravity Field Using Juno Measurements, Trajectory Estimation Analysis, and a Flow Model Optimization

The upcoming Juno spacecraft measurements have the potential of improving our knowledge of Jupiter’s gravity field. The analysis of the Juno Doppler data will provide a very accurate reconstruction of spatial gravity variations, but these measurements will be very accurate only over a limited latitudinal range. In order to deduce the full gravity field of Jupiter, additional information needs to be incorporated into the analysis, especially regarding the Jovian flow structure and its depth, which can influence the measured gravity field. In this study we propose a new iterative method for the estimation of the Jupiter gravity field, using a simulated Juno trajectory, a trajectory estimation model, and an adjoint-based inverse model for the flow dynamics. We test this method both for zonal harmonics only and with a full gravity field including tesseral harmonics. The results show that this method can fit some of the gravitational harmonics better to the “measured” harmonics, mainly because of the added information from the dynamical model, which includes the flow structure. Thus, it is suggested that the method presented here has the potential of improving the accuracy of the expected gravity harmonics estimated from the Juno and Cassini radio science experiments.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Cutting out the middleman: calibrating and validating a dynamic vegetation model (ED2-PROSPECT5) using remotely sensed surface reflectance

Canopy radiative transfer is the primary mechanism by which models relate vegetation composition and state to the surface energy balance, which is important to light- and temperature-sensitive plant processes as well as understanding land–atmosphere feedbacks. In addition, certain parameters (e.g., specific leaf area, SLA) that have an outsized influence on vegetation model behavior can be constrained by observations of shortwave reflectance, thus reducing model predictive uncertainty. Importantly, calibrating against radiative transfer outputs allows models to directly use remote sensing reflectance products without relying on highly derived products (such as MODIS leaf area index) whose assumptions may be incompatible with the target vegetation model and whose uncertainties are usually not well quantified. Here, we created the EDR model by coupling the two-stream representation of canopy radiative transfer in the Ecosystem Demography model version 2 (ED2) with a leaf radiative transfer model (PROSPECT-5) and a simple soil reflectance model to predict full-range, high-spectral-resolution surface reflectance that is dependent on the underlying ED2 model state. We then calibrated this model against estimates of hemispherical reflectance (corrected for directional effects) from the NASA Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) and survey data from 54 temperate forest plots in the northeastern United States. The calibration significantly reduced uncertainty in model parameters related to leaf biochemistry and morphology and canopy structure for five plant functional types.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Taking off the training wheels: the properties of a dynamic vegetation model without climate envelopes

We describe an implementation of the Ecosystem Demography (ED) concept in the Community Land Model. The structure of CLM(ED) and the physiological and structural modifications applied to the CLM are presented. A major motivation of this development is to allow the prediction of biome boundaries directly from plant physiological traits via their competitive interactions. Here we investigate the performance of the model for an example biome boundary in Eastern North America. We explore the sensitivity of the predicted biome boundaries and ecosystem properties to the variation of leaf properties determined by the parameter space defined by the GLOPNET global leaf trait database. Further, we investigate the impact of four sequential alterations to the structural assumptions in the model governing the relative carbon economy of deciduous and evergreen plants. The default assumption is that the costs and benefits of deciduous vs. evergreen leaf strategies, in terms of carbon assimilation and expenditure, can reproduce the geographical structure of biome boundaries and ecosystem functioning. We find some support for this assumption, but only under particular combinations of model traits and structural assumptions. Many questions remain regarding the preferred methods for deployment of plant trait information in land surface models. In some cases, plant traits might best be closely linked with each other, but we also find support for direct linkages to environmental conditions. We advocate for intensified study of the costs and benefits of plant life history strategies in different environments, and for the increased use of parametric and structural ensembles in the development and analysis of complex vegetation models.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1965

Flexure support system protects thermally and dynamically loaded models

The design of an eight legged flexure support system which permits differential thermal expansion of thin skinned models subjected to high temperatures is done by setting the lengthwise axes of the supporting legs approximately normal to the line of absolute motion of the model supported.

Crumpler, W. B.↗
NASA NTRS1968

A revised dynamic otolith model

Control theory applied to analysis of vestibular function for obtaining mathematical model of semicircular canals and otolith organs

Meiry, J. L.↗
NASA NTRS1970

Dynamic control models of the semicircular canals

Vestibular system semicircular canals mathematical model determination of galvanic stimulation and directional preponderance, considering visual, postural and vehicle orientation feedback loops

Young, L. R.↗
NASA NTRS1972

Dynamic mass modeling and geophysical analysis of lunar maria based on Apollo tracking data

A series of lunar gravity analyses were carried out using unified S-band tracking network data obtained from Apollos 8, 10, 11, 12, 14, and 15. The progress obtained to date is summarized as it relates to the estimation of lunar mass distributions and their geologic interpretation. The analyses reported are of two distinct types. The first type consists of data obtained at two ranges of altitude to estimate the total mass associated with various lunar features employing a point mass assumption. The second type consists of detailed analyses of Apollo 14 tracking data.

Strange, W. E.↗
NASA NTRS1977

A three-dimensional model of dynamical processes in the Venus atmosphere

Three-dimensional calculations of the circulation of the Venus atmosphere have resulted in mean zonal winds in the same direction and of the same magnitude as those observed; i.e., retrograde with speeds of the order of 100 m/s. The solutions exhibit other observed properties of the circulation: small horizontal temperature contrasts with the larger variations being between equator and pole, meridional velocities at mid and low latitudes less than 10 m/s, and the existence of planetary waves which at certain times show vertical flow-field contours in a horizontal Y configuration. The mechanism maintaining the large zonal winds is a nonlinear instability involving both the mean meridional circulation and planetary-scale eddies. The meridional circulation is the principal means by which zonal momentum is transported vertically. Planetary-scale eddies are the principal means by which potential energy is released, and they are also significant in transporting angular momentum horizontally. Planetary rotation plays an important role in initially generating the mean zonal winds starting from rest. Initial conditions affect the characteristics of the solutions, including the magnitude of the mean zonal velocity and whether or not planetary waves are generated.

Young, R. E.↗
NASA NTRS1978

Dynamic MHD modeling of the solar wind disturbances during the August 1972 events

A time-dependent one-dimensional MHD theoretical model is tested by using plasma and magnetic field observations of Pioneer 9 and Pioneer 10 during the August 1972 events on the sun and in the interplanetary medium. These spacecraft were nearly aligned along a common heliocentric radius during these events, considered now to be the most spectacular and best-documented events during solar cycle 20. The observations of Pioneer 9 at 0.78 AU were used as input for the theoretical model. The plasma and magnetic field forcing functions were superimposed upon a preexisting ambient solar wind at this inner boundary, and the response was simulated as far as 8 AU. The simulated output at 2.2 AU is compared directly with the Pioneer 10 observations at 2.2 AU. Qualitative comparison is good, although several limitations of the one-dimensional theory are noted.

Dryer, M.↗
NASA NTRS1978

Dynamic MHD modeling of solar wind corotating stream interaction regions observed by Pioneer 10 and 11

The use of the Pioneer 10 and 11 projects to test an MHD one-dimensional time-dependent model of corotating solar wind streams during the period from Sept. 30 to Nov. 25, 1973 is described. During this period, five or six corotating interaction regions streamed past the two spacecraft, and, as a result of multiple-spacecraft radial alignment and temporally varying conditions at the solar wind source, the pattern predicted by the Steinolfson et al. (1975) model could be compared with observations. The results, in general, support the validity of the model, although the neglect of thermal energy exchange leads to incorrect values for the proton temperature. A detailed analysis of a stream is discussed.

Dryer, M.↗