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At least 757 records · Page 42

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DOE OSTI2022

The EGS Collab Project – Stimulations at Two Depths

The EGS Collab project, supported by the US Department of Energy, is performing intensively monitored rock stimulation and flow tests at the 10-m scale in an underground research laboratory to address challenges in implementing enhanced geothermal systems (EGS). Data and observations from the field tests are compared to simulations to understand processes and build confidence in numerical modeling of the processes. We have completed Experiment 1 (of 3), which examined hydraulic fracturing in a well-characterized underground fractured phyllite test bed at a depth of approximately 1.5 km at the Sanford Underground Research Facility (SURF) in Lead, South Dakota. Testbed characterization included fracture mapping, borehole acoustic and optical televiewers, full waveform sonic, conductivity, resistivity, temperature, campaign p- and s-wave investigations and electrical resistance tomography. Borehole geophysical techniques including passive seismic, continuous active source seismic monitoring, electrical resistance tomography, fiber-based distributed strain, distributed temperature, and distributed acoustic monitoring, were used to carefully monitor stimulation events and flow tests. More than a dozen stimulations and nearly one year of flow tests were performed. Quality data and detailed observations were collected and analyzed during stimulation and water flow tests using ambient temperature and chilled water. We achieved adaptive control of the tests using real-time monitoring and rapid dissemination of data and near-real-time simulation. More detailed numerical simulation was performed to answer key experimental design questions, forecast fracture propagation trajectories and extents, and analyze and evaluate results. Data are freely available from the Geothermal Data Repository. Experiment 2 examines the potential for hydraulic shearing in amphibolite at a depth of about 1.25 km at SURF. This site has a different set of stress and fracture conditions than Experiment 1. The Experiment 2 testbed consists of nine subhorizontal boreholes configured in two fans of two boreholes which surround the testbed and contain grouted-in electrical resistance tomography, seismic sensors, active seismic sources and distributed fiber sensors. A “five-spot” set of test wells that extends from a custom mined alcove includes an injection well and four production/monitoring wells. The testbed was characterized geophysically and hydrologically, and three stimulations have been performed using the Step-Rate Injection Method for Fracture In-Situ Properties (SIMFIP) tool to measure strains, and a new strain quantifying tool (downhole robotic strain analysis tool -DORSA) was deployed in a monitoring hole during stimulation. Real-time data were broadcast during stimulations to allow real-time response to arising issues.

EGS Collab, Enhanced Geothermal Systems, EGS, fiel↗

DOE OSTI2022

Diffraction and thermal effect of a Bessel-Gaussian laser for Ag nanoparticle deposition

Nanoparticles are known to sinter at much lower temperatures than the corresponding bulk or micro size particles. A laser-assisted sintering process is considered in this study to sinter Ag nanoparticles by dispensing Ag paste onto an indium tin oxide-coated Si substrate. The Gaussian beam of a CO 2 laser source is propagated through axicon and biconvex lenses, and the resulting hollow beam is focused on the Ag paste with a hollow parabolic mirror. A Bessel-Gaussian irradiance distribution is obtained at the focal plane of the parabolic mirror due to the interference of the hollow laser cone. The Fresnel diffraction approximation is considered to determine the phasor of the laser and an analytical approach is implemented to calculate the irradiance distribution of the Bessel-Gaussian beam. This irradiance distribution is utilized as a heat source in a heat conduction model and the temperature distribution is analyzed for thin Ag films formed during the laser sintering of Ag nanoparticles. An analytical expression is obtained for the temperature distribution by solving the heat conduction equation using Fourier transform for finite media. The widths of the deposited Ag lines are predicted from the temperature profiles and the model predictions compare well with the experimental results. The isotherms are found to be geometrically noncongruent with convex and concave tips depending on the locally maximum and minimum irradiances of the Bessel-Gaussian beam, respectively. The convex and concave tips, however, appear in the same isotherm for sufficiently high substrate speed relative to the laser beam.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

DOE OSTI2025

Ultra-high Bandwidth, Ultra-high Dynamic Range X-Ray Shock Characterization via Photonic Integrated Circuit

Nuclear weapon component assessment tests at the Z Machine rely on accurate X-ray yield measurements for model validation, design and analysis of component survivability, and source optimization. Yield measurement devices currently used do not provide the requisite certainty to enable accurate and efficient data analysis of test results, which leads to an increase in Z-shots required for evaluation, longer device development times, and higher operation costs. Additionally, current X-ray flux detectors lack high temporal resolution at the tails. Similarly, shock measurement techniques used for component assessment often lack the ability to spatially resolve wave behavior thereby limiting the ability to measure shock propagation dynamics needed to design the next generation of ND components. Here we present the development of a photonic micro-calorimeter and shock sensor consisting of meter-long waveguide spirals that are optomechanically coupled to X-ray absorbing layers to characterize yield and shock propagation at nanosecond timescales.

42 ENGINEERING↗

NASA NTRS1984

The response of a nonlinear, time-dependent, baroclinic model of the atmosphere to tropical thermal forcing

A multi-level, sigma coordinate, primitive equation atmospheric model has been utilized to study both the tropical and extratropical response to an isolated region of steady thermal forcing in the tropics. The nonlinear response during the first 28 days of the simulation is described. The response can be generally characterized by two distinct components. The first component is a quasi-stationary disturbance which extends eastward and poleward away from the source region along a 'great circle' path. The structure of this disturbance is essentially barotropic away from the source region. The second component is a growing baroclinic wave propagating zonally at mid-latitudes. Significantly, this disturbance is apparently the result of baroclinic instability induced by the quasi-stationary wavetrain. The discussion is predominantly heuristic in form and relies heavily on graphical presentation and quasi-geostrophic theory to interpret the response and individual components of the thermodynamic energy and momentum equations.

Grose, W. L.↗

NASA NTRS1998

Application of the Shuttle Laser Altimeter in an Accuracy Assessment of Global 1-Kilometer Digital Elevation Data

Shuttle Laser Altimeter (SLA) data have been used to evaluate the accuracy of GTOPO30, the first comprehensive, 1 km resolution, global topographic data set. GTOPO30 was developed by the USGS Eros Data Center (EDC), in part, to address NASA's needs for a global topographic model in support of remote sensing instruments aboard the Earth Observing System AM-1 spacecraft. SLA flew as a part of the STS-72 mission in January, 1996 observing the latitude band from +/- 28.5 deg, and on STS-85 in August, 1997 extending the observations to +/- 57 deg. Combining the SLA ranging data with shuttle position and pointing knowledge yields surface elevation data of very high vertical accuracy in an Earth-centered, absolute reference frame (2.8 m rms difference for SLA-01 with respect to ocean reference surface). Use of the well-determined mean sea surface reference for calibration allows propagation of high accuracy altimetry onto the continents. 436,635 SLA-01 land elevations were compared to the GTOPO30 grid after conversion to a mean sea level vertical datum using the Earth Geoid Model 96, jointly developed by Goddard and NIMA. The comparison reveals systematic elevation biases in southern Asia, Africa, Australia, and south America on the order 10's to 100 meters in the GTOPO30 compilation on spatial scales of 100's to 1000's of kilometers. These biases are likely due to vertical datum errors in the topographic source materials used to compile GTOPO30, which primarily consist of Defense Mapping Agency (DMA) digital elevation and topographic map products. These biases imply that elevation corrections applied to land gravity measurements using these DMA source materials will be biased, leading to errors in geoid models incorporating these land gravity data.

Harding, David J.↗

DOE OSTI2022

Characterization of Acoustic Emissions From Analogue Rocks Using Sparse Regression‐DMDc

Abstract Moisture loss in rock is known to generate acoustic emissions (AE). Phenomena that result in AE during drying are related to the movement of fluids through the pores and induced‐cracks that arise from differential mineral shrinkage, especially in clay‐bearing rock. AE from the movement of fluids occurs from the reconfiguration of fluid interfaces during drying, while AE from mineral shrinkage involves the debonding within or between minerals. Here, analogue rock samples were used to examine the differences in the AE signatures when one or both AE source‐types are present. An unsupervised sparse regression model, Dynamic Mode Decomposition with control, that extends Dynamic Mode Decomposition is used to characterize the AE signals recorded during the drying of porous analogue rock samples fabricated with ordinary Portland cement, with and without clay. This method can effectively and accurately reconstruct acoustic signals emitted from samples that only experience moisture loss without cracking. However, the method struggles to reconstruct signals from samples with intricate crack networks that formed during drying because AE generating mechanisms can emit contemporaneously, and the resulting waves propagate through drying‐induced cracks that can lead to multiple internal reflections. Thus, the differential reconstruction accuracy of time series generated by different underlying physical processes provides a robust filter for reducing large data catalogs. In general, both dynamics and sparse initiating events are learned directly from data and this method exposes a data hierarchy based on the complexity of the intrinsic dynamics.

58 GEOSCIENCES↗

NASA NTRS1978

Use of coherence and phase data between two receivers in evaluation of noise environments

For certain types of noise control problems, where transducers cannot be mounted on suspected sources, valuable information can often be obtained by comparing the coherence and phase data measured between two closely spaced microphones with analytical models deduced from the physics of the problem. However, the application of such analysis techniques must be pursued with care, particularly when the measurements are made in a reverberant area. A simple illustration is presented where the acoustic field in the test section of a wind tunnel is evaluated by modelling the field as a combination of diffuse noise due to the boundary layer turbulence in the test section and propagating noise generated by the tunnel fan and possible flow disturbances outside the test section. The coherence and phase between two closely spaced microphones in the tunnel test section are predicted for various ratios of diffuse to propagating noise contributions and compared to actual measurements under several different tunnel operating conditions.

Piersol, A. G.↗

NASA NTRS2000

Test System to Study the Ignition of Metals by Polymers in Oxygen

A new test system that uses Laser energy to ignite a polymer promoter has been developed at the NASA White Sands Test Facility. It will facilitate the study of the spread of fire from a burning polymer material to the metal surrounding it. The system can be used to answer questions regarding the effects of configuration on ignition and combustion. The data obtained from this test could also be used to develop mathematical models for analyzing the effects of configuration on ignition and combustion. The system features a 10,000-psi (69-MPa) test chamber with sight glass windows on either end and a 25-watt carbon dioxide Laser for an ignition source. The test system can be used with gaseous oxygen, nitrogen or any mixture of the two gases. To minimize the effect of preheating the metallic, the polymer is ignited with a minimal amount of Laser energy. Igniting the polymer in this fashion also simplifies the thermodynamic analysis of the ignition and propagation reactions. The system is very robust, versatile and straightforward to use. Depending on the test pressure and configuration, the test system operator can perform as many as 20 tests per day. Test results verify that ignition and combustion of the metallic sample is not only dependent on pressure, material type and temperature, but configuration of both the polymer promoter and metallic sample. Both 6061 aluminum and 316 stainless steel 0.25-inch (6.35-mm) diameter rods with a standard 0-ring groove were tested with Buna-N, Silicone, Teflon and Viton 0-rings. The system ignited all four types of 0-rings in oxygen at pressures ranging from ambient to 10,000 psi (69 MPa). However, neither the stainless steel nor the aluminum rods on which the O-rings were mounted ignited in any test conditions. Future testing may be done on the 0.25-inch (6.35-mm) rod and O-ring configuration to evaluate the lack of ignition in these tests. Future configurations may include a plug of polymer in the base of the sample and replicas of fire-damaged components. Furthermore, the test system may be used in the future to analyze the oxidation rate of Laser-heated metals in gaseous oxygen.

Shoffstall, Michael S.↗

NASA NTRS1994

The Influence of Finite-size Sources in Acousto-ultrasonics

This work explores the effects that the finite normal axisymmetric traction loading of an infinite isotropic plate has on wave propagation in acousto-ultrasonics (AU), in which guided waves are created using two normal incidence transducers. Although the work also addresses the effects of the transducer pressure distribution and pulse shape, this thesis concentrates on two main questions: how does the transducer's diameter control the phase velocity and frequency spectrum of the response, and how does the plate thickness relate to the plate's excitability? The mathematics of the time-harmonic solution and the physical principles and the practical considerations for AU wave generation are explained. Transient sources are modeled by the linear superposition of the time-harmonic solutions found using the Hankel transform and they are then compared to experimental data to provide insight into the relation between the size of the transducer and the preferred phase velocity.

Pavlakovic, Brian N.↗

NASA NTRS1997

Response of High Subsonic Jet to Nonaxisymmetric Disturbances

A model of sound generated in a high subsonic (Mach 0.9) circular jet is solved numerically in cylindrical coordinates for nonaxisymmetric disturbances. The jet is excited by transient mass injection by a finite duration pulse via a modulated ring source. The nonaxisymmetric solution is computed for long times after the initial disturbance has exited the computational domain. The long time behavior of the jet is dominated by vorticity and pressure disturbances generated at the nozzle lip and growing as they convect down-stream in the jet. These disturbances generate sound as they propagate. The primary non-axisymmetric effect that we simulate is that of a flapping mode where regions of high and low pressure alternate on opposite sides of the jet. The predominant feature of this mode is the appearance of relatively large deviations of the pressure from the ambient pressure on opposite sides of the jet and the convection of these regions downstream. We illustrate flow field, near field and far field data. Important nonaxisymmetric characteristics of the near and flow field disturbances include roughly periodic pressure elevations and depressions at opposite values of the azimuthal angle psi. These correspond to pressure disturbances propagating in the axial direction. The azimuthal velocity exhibits a sinusoidal dependence on psi with similar roughly periodic disturbances. For every azimuthal angle psi, the jet radiation peaks about 30 deg. from the jet axis, however there is now a pronounced dependence of the far field radiation pattern on psi.

Bayliss, A.↗

DOE OSTI2020

Recent advances in the quantification of uncertainties in reaction theory

Uncertainty quantification has become increasingly more prominent in nuclear physics over the past several years. In few-body reaction theory, there are four main sources that contribute to the uncertainties in the calculated observables: the effective potentials, approximations made to the few-body problem, structure functions, and degrees of freedom left out of the model space. In this work, we illustrate some of the features that can be obtained when modern statistical tools are applied in the context of nuclear reactions. This work consists of a summary of the progress that has been made in quantifying theoretical uncertainties in this domain, focusing primarily on those uncertainties coming from the effective optical potential as well as their propagation within various reaction theories. We use, as the central example, reactions on the doubly-magic stable nucleus 40 Ca, namely neutron and proton elastic scattering and single-nucleon transfer 40 Ca(d,p) 41 Ca. First, we show different optimization schemes used to constrain the optical potential from differential cross sections and other experimental constraints; we then discuss how these uncertainties propagate to the transfer cross section, comparing two reaction theories. Finally, we finish by laying out our future plans.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

NASA NTRS1981

Mesospheric heating due to convectively excited gravity waves - A case study

A series of at least daily rocket soundings of the mesosphere at Wallops Island, Virginia (37 deg 50 min N, 75 deg 29 min W), in August and September 1976 reveal near simultaneity between rapid temperature rises and tropospheric convection in the form of squall lines. A multilevel numerical model is developed to test the hypothesis that the convection and warmings are related via internal gravity waves. Some features of the model are (1) the wave energy source is expressed in terms of cloud-base mass flux, plume diameter and buoyant updraft velocity; (2) the turbulent-viscous gravity wave dissipation is limited to above 55 km and is parameterized on the basis of findings by Hines (1965). Significant findings are: (1) mesospheric heating rates of the same order as those observed result for reasonable values of the convective parameters and in situ dissipation time scales; (2) only gravity waves confined to a well-defined wavelength and frequency interval are able to propagate upward to mesospheric altitudes; (3) heating rates are strongly dependent on plume diameter and updraft velocity; and (4) for a given cloud-base mass flux, heating rates are optimized for a plume updraft velocity of 10 m/s.

Clark, J. H. E.↗

NASA NTRS1989

The generalized drift flux approach: Identification of the void-drift closure law

The main characteristics and the potential advantages of generalized drift flux models are presented. In particular it is stressed that the issue on the propagation properties and on the mathematical nature (hyperbolic or not) of the model and the problem of closure are easier to tackle than in two fluid models. The problem of identifying the differential void-drift closure law inherent to generalized drift flux models is then addressed. Such a void-drift closure, based on wave properties, is proposed for bubbly flows. It involves a drift relaxation time which is of the order of 0.25 s. It is observed that, although wave properties provide essential closure validity tests, they do not represent an easily usable source of quantitative information on the closure laws.

Boure, J. A.↗

NASA NTRS1991

Broadband shock-associated noise from supersonic jets in flight

The stochastic model theory of broadband shock-associated noise from supersonic jets, developed earlier (Tam, 1987, 1990), is extended to jets in flight. Forward flight affects broadband shock-associated noise generation through noise source modification. It also affects the intensity and characteristics of the noise radiated in a given direction through the mean flow convection effect. Noise source modification arises when the external flow associated with forward flight alters the mean velocity profile and shock cell structure of the jet. The mean flow convection effect arises because the radiated sound waves now have to propagate through a moving medium to reach the observation point. The present theory suggests that both the noise source modification effect and the mean flow convection effect would produce narrower broadband shock-associated noise spectral peaks with lower peak frequencies. The theory is further extended to the case of a supersonic jet embedded in an open wind tunnel bounded by a vortex sheet. Detalied comparisons between the calculated results and the measurements of Norum and Shearin (1984, 1986) are reported here. Very good agreements are found over a broad range of jet Mach numbers and wind tunnel Mach numbers.

Tam, C. K. W.↗

NASA NTRS1985

Acoustic propagation in a thermally stratified atmosphere

This report describes the activities during the fifth six month period of the investigation of acoustic propagation in the atmosphere with a realistic temperature profile. Progress has been achieved in two major directions: comparisons between the lapse model and experimental data taken by NASA during the second tower experiment, and development of a model propagation in an inversion. Data from the second tower experiment became available near the end of 1984 and some comparisons have been carried out, but this work is not complete. Problems with the temperature profiler during the experiment have produced temperature profiles that are difficult to fit the assumed variation of temperature with height, but in cases where reasonable fits have been obtained agreement between the model and the experiments are close. The major weaknesses in the model appear to be the presence of discontinuities in some regions, the low sound levels predicted near the source height, and difficulties with the argument of the Hankel function being outside the allowable range. Work on the inversion model has progressed slowly, and the rays for that case are discussed along with a simple energy conservation model of sound level enhancement in the inversion case.

Vanmoorhem, W. K.↗

NASA NTRS2003

Numerical and Experimental Determination of the Geometric Far Field for Round Jets

To reduce ambiguity in the reporting of far field jet noise, three round jets operating at subsonic conditions have recently been studied at the NASA Glenn Research Center. The goal of the investigation was to determine the location of the geometric far field both numerically and experimentally. The combination of the WIND Reynolds-Averaged Navier-Stokes solver and the MGBK jet noise prediction code was used for the computations, and the experimental data was collected in the Aeroacoustic Propulsion Laboratory. While noise sources are distributed throughout the jet plume, at great distances from the nozzle the noise will appear to be emanating from a point source and the assumption of linear propagation is valid. Closer to the jet, nonlinear propagation may be a problem, along with the known geometric issues. By comparing sound spectra at different distances from the jet, both from computational methods that assume linear propagation, and from experiments, the contributions of geometry and nonlinearity can be separately ascertained and the required measurement distance for valid experiments can be established. It is found that while the shortest arc considered here (approx. 8D) was already in the geometric far field for the high frequency sound (St greater than 2.0), the low frequency noise due to its extended source distribution reached the geometric far field at or about 50D. It is also found that sound spectra at far downstream angles does not strictly scale on Strouhal number, an observation that current modeling does not capture.

Koch, L. Danielle↗

NASA NTRS2012

A Framework for Simulation of Aircraft Flyover Noise Through a Non-Standard Atmosphere

This paper describes a new framework for the simulation of aircraft flyover noise through a non-standard atmosphere. Central to the framework is a ray-tracing algorithm which defines multiple curved propagation paths, if the atmosphere allows, between the moving source and listener. Because each path has a different emission angle, synthesis of the sound at the source must be performed independently for each path. The time delay, spreading loss and absorption (ground and atmosphere) are integrated along each path, and applied to each synthesized aircraft noise source to simulate a flyover. A final step assigns each resulting signal to its corresponding receiver angle for the simulation of a flyover in a virtual reality environment. Spectrograms of the results from a straight path and a curved path modeling assumption are shown. When the aircraft is at close range, the straight path results are valid. Differences appear especially when the source is relatively far away at shallow elevation angles. These differences, however, are not significant in common sound metrics. While the framework used in this work performs off-line processing, it is conducive to real-time implementation.

Arntzen, Michael↗

NASA NTRSDate not supplied

Towards an Optimal Estimation Retrieval of Cirrus Cloud Optical and Microphysical Properties Using Hyperspectral Shortwave Instruments and A Fast Radiative Transfer Algorithm

Cirrus cloud retrieval products (here, cloud optical depth, effective particle size, and cloud top height) are important inputs into numerical weather and climate models. Uncertainties in such retrieval products, as a matter of course, propagate downstream, impacting model calculations. Improvements in high-quality global cirrus cloud optical and microphysical data products from satellite observations are needed to understand and reduce retrieval uncertainties. Hyperspectral shortwave instruments produce high-resolution and information-dense spectra, thus offering the opportunity to reduce uncertainties in retrieval products. We are in the process of developing a retrieval that uses the very fast Principal Component Radiative Transfer Model in the solar spectral region (PCRTM-Solar) in the forward model calculations. This retrieval will use measured reflectances from the NASA Earth Surface Mineral Dust Source Investigation (EMIT) and the forthcoming Climate Absolute Radiance and Refractivity Observatory Pathfinder (CLARREO-Pathfinder) instruments. In this manuscript we present progress towards a reference retrieval employing a widely used, verified, accurate, yet computationally slower radiative transfer modeling technique. The reference retrieval, while too slow for using the complete hyperspectral measurement, will allow us to study the behavior of retrieval products and help us verify results from our in-development fast retrieval. Both retrievals will use the optimal estimation retrieval framework. In this manuscript we present results from an uncertainty analysis considering three uncertainty sources for a cirrus cloud retrieval in the form of error covariance matrices: reflectance uncertainty due to water vapor, the reflectance uncertainty due to ice crystal scattering assumptions, and the instrument measurement uncertainty. Results show that the uncertainty due to habit selection is the largest, while that due to water vapor is at most 0.6% relative to channel reflectance. As a first step, the retrieval is being designed for single layer ice clouds over open ocean water.

Cirrus cloud↗