Search NASA⌕ Search

SEARCH · Search NASA

Results for “force fields”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,621 records · Page 90
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Radial energy transport by magnetospheric ULF waves: Effects of magnetic curvature and plasma pressure

The 'radial' transport of energy by internal ULF waves, stimulated by dayside magnetospheric boundary oscillations, is analyzed in the framework of one-fluid magnetohydrodynamics. (the term radial is used here to denote the direction orthogonal to geomagnetic flux surfaces.) The model for the inhomogeneous magnetospheric plasma and background magnetic field is axisymmetric and includes radial and parallel variations in the magnetic field, magnetic curvature, plasma density, and low but finite plasma pressure. The radial mode structure of the coupled fast and intermediate MHD waves is determined by numerical solution of the inhomogeneous wave equation; the parallel mode structure is characterized by a Wentzel-Kramer-Brillouin (WKB) approximation. Ionospheric dissipation is modeled by allowing the parallel wave number to be complex. For boudnary oscillations with frequencies in the range from 10 to 48 mHz, and using a dipole model for the background magnetic field, the combined effects of magnetic curvature and finite plasma pressure are shown to (1) enhance the amplitude of field line resonances by as much as a factor of 2 relative to values obtained in a cold plasma or box-model approximation for the dayside magnetosphere; (2) increase the energy flux delivered to a given resonance by a factor of 2-4; and (3) broaden the spectral width of the resonance by a factor of 2-3. The effects are attributed to the existence of an 'Alfven buoyancy oscillation,' which approaches the usual shear mode Alfven wave at resonance, but unlike the shear Alfven mode, it is dispersive at short perpendicular wavelengths. The form of dispersion is analogous to that of an internal atmospheric gravity wave, with the magnetic tension of the curved background field providing the restoring force and allowing radial propagation of the mode. For nominal dayside parameters, the propagation band of the Alfven buoyancy wave occurs between the location of its (field line) resonance and that of the fast mode cutoff that exists at larger radial distances.

Kouznetsov, Igor↗
NASA NTRS2018

Comparison of MERRA-2 and ECCO-V4 Ocean Surface Heat Fluxes: Consequences of Different Forcing Feedbacks on Ocean Circulation and Implications for Climate Data Assimilation

Forcing ocean models with reanalysis data is a common practice in ocean modeling. As part of this practice, prescribed atmospheric state variables and interactive ocean SST (Sea Surface Temperature) are used to calculate fluxes between the ocean and the atmosphere. When forcing an ocean model with reanalysis fields, errors in the reanalysis data, errors in the ocean model and errors in the forcing formulation will generate a different solution compared to other ocean reanalysis solutions (which also have their own errors). As a first step towards a consistent coupled ocean-atmosphere reanalysis, we compare surface heat fluxes from a state-of-the-art atmospheric reanalysis, the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2), to heat fluxes from a state-of-the-art oceanic reanalysis, the Estimating the Circulation and Climate of the Ocean Version 4, Release 2 (ECCO-v4). Then, we investigate the errors associated with the MITgcm (Massachusetts Institute of Technology general circulation model) ocean model in its ECCO-v4 ocean reanalysis configuration (1992-2011) when it is forced with MERRA- 2 atmospheric reanalysis fields instead of with the ECCO-v4 adjoint optimized ERA-interim state variables. This is done by forcing ECCO-v4 ocean with and without feedbacks from MERRA-2 related to turbulent fluxes of heat and moisture and the outgoing long wave radiation. In addition, we introduce an intermediate forcing method that includes only the feedback from the interactive outgoing long wave radiation. The resulting ocean circulation is compared with ECCO-v4 reanalysis and in-situ observations. We show that, without feedbacks, imbalances in the energy and the hydrological cycles of MERRA-2 (which are directly related to the fact it was created without interactive ocean) result in considerable SST drifts and a large reduction in sea level. The bulk formulae and interactive outgoing long wave radiation, although providing air-sea feedbacks and reducing model-data misfit, strongly relax the ocean to observed SST and may result in unwanted features such as large change in the water budget. These features have implications in a desired forcing recipe to be used. The results strongly and unambiguously argue for next generation data assimilation climate studies to involve fully coupled systems.

MERRA-2↗
NASA NTRS1982

Turbofan forced mixer-nozzle internal flowfield. Volume 1: A benchmark experimental study

An experimental investigation of the flow field within a model turbofan forced mixer nozzle is described. Velocity and thermodynamic state variable data for use in assessing the accuracy and assisting the further development of computational procedures for predicting the flow field within mixer nozzles are provided. Velocity and temperature data suggested that the nozzle mixing process was dominated by circulations (secondary flows) of a length scale on the order the lobe dimensions which were associated with strong radial velocities observed near the lobe exit plane. The 'benchmark' model mixer experiment conducted for code assessment purposes is discussed.

Paterson, R. W.↗
DOE OSTI2024

Development of Superconducting RF Cavity in Traveling-Wave Regime at Fermilab

Niobium Superconducting RF (SRF) cavities have a theoretical peak magnetic field which limits the accelerating field to 50-60 MV/m. Presently, all SRF cavities operate in a Standing Wave (SW) resonance field in which particles experience an accelerating force alternating from zero to peak. In contrast, a resonance field in Traveling Wave (TW) mode propagates along with a structure, so particles in such field can experience a constant acceleration force and could have higher energy gain than that of SW mode. This phenomenon is defined by the cavity’s transit time factor, T. A TW structure proposed in an early study achieves T ~0.9, suggesting an increase in acceleration per structure by more than 20% compared to a SW structure (T ~0.7). The early stages of developments had been funded by several SBIR grants to Euclid Techlabs and completed in collaboration with Fermilab through a 1-cell prototype and a proof-of-principle 3-cell TW cavity. It demonstrated the TW resonance excitation at room temperature in the “as-fabricated” 3-cell structure. Here we report recent progresses and the first cryogenic testing of the 3-cell TW cavity in 2 K liquid helium at Fermilab.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1972

Photospheric magnetic fields

Knowledge on the nature of magnetic fields on the solar surface is reviewed. At least a large part of the magnetic flux in the solar surface is confined to small bundles of lines of force within which the field strength is of the order of 500 gauss. Magnetic fields are closely associated with all types of solar activity. Magnetic flux appears at the surface at the clearly defined birth or regeneration of activity of an active region. As the region ages, the magnetic flux migrates to form large-scale patterns and the polar fields. Some manifestations of the large-scale distribution are discussed.

Howard, R.↗
NASA NTRS1974

High latitude ionospheric winds related to solar-interplanetary conditions

Two recent results imply that the distribution of winds in the polar ionosphere should change as a function of the direction of the interplanetary magnetic field. From the motions of chemically released ion and neutral clouds, it is apparent that neutral winds in the high latitude ionosphere are driven principally by ion drag forces. OGO-6 electric field measurements have demonstrated that there are definite relationships between the time latitude distribution of ionospheric plasma convection and interplanetary magnetic field parameters, and also that the distribution is most sensitive to the azimuthal angle of the interplanetary field. The lower altitude, meteorological effects of these externally driven ionospheric winds are not known. However, observations of infrasonic waves following sudden ionization enhancements indicate the existence of momentum transfer.

Heppner, J. P.↗
NASA NTRS1975

High-latitude ionospheric winds related to solar-interplanetary conditions

Treated jointly, two recent results imply that the distribution of winds in the polar ionosphere should change as a function of the direction of the interplanetary magnetic field. From the motions of chemically released ion and neutral clouds, it is apparent that neutral winds in the high-latitude ionosphere are driven principally by ion drag forces. OGO 6 electric field measurements demonstrate that there are definite relationships between the time/latitude distribution of ionospheric plasma convection and interplanetary magnetic field parameters, and also that the distribution is most sensitive to the azimuthal angle of the inter planetary field. Although direct neutral wind to interplanetary magnetic field comparisons are not available, logic clearly implies a close relationship. Observations of infrasonic waves following sudden ionization enhancements indicate the existence of momentum transfer.

Heppner, J. P.↗
NASA NTRS1999

Ames Optimized TCA Configuration

Configuration design at Ames was carried out with the SYN87-SB (single block) Euler code using a 193 x 49 x 65 C-H grid. The Euler solver is coupled to the constrained (NPSOL) and the unconstrained (QNMDIF) optimization packages. Since the single block grid is able to model only wing-body configurations, the nacelle/diverter effects were included in the optimization process by SYN87's option to superimpose the nacelle/diverter interference pressures on the wing. These interference pressures were calculated using the AIRPLANE code. AIRPLANE is an Euler solver that uses a unstructured tetrahedral mesh and is capable of computations about arbitrary complete configurations. In addition, the buoyancy effects of the nacelle/diverters were also included in the design process by imposing the pressure field obtained during the design process onto the triangulated surfaces of the nacelle/diverter mesh generated by AIRPLANE. The interference pressures and nacelle buoyancy effects are added to the final forces after each flow field calculation. Full details of the (recently enhanced) ghost nacelle capability are given in a related talk. The pseudo nacelle corrections were greatly improved during this design cycle. During the Ref H and Cycle 1 design activities, the nacelles were only translated and pitched. In the cycle 2 design effort the nacelles can translate vertically, and pitch to accommodate the changes in the lower surface geometry. The diverter heights (between their leading and trailing edges) were modified during design as the shape of the lower wing changed, with the drag of the diverter changing accordingly. Both adjoint and finite difference gradients were used during optimization. The adjoint-based gradients were found to give good direction in the design space for configurations near the starting point, but as the design approached a minimum, the finite difference gradients were found to be more accurate. Use of finite difference gradients was limited by the CPU time limit available on the Cray machines. A typical optimization run using finite difference gradients can use only 30 to 40 design variables and one optimization iteration within the 8 hour queue limit for the chosen grid size and convergence level. The efficiency afforded by the adjoint method allowed for 50-120 design variables and 5-10 optimization iterations in the 8 hour queue. Geometric perturbations to the wing and fuselage were made using the Hicks/Henne (HH) shape functions. The HH functions were distributed uniformly along the chords of the wing defining sections and lofted linearly. During single-surface design, constraints on thickness and volume at selected wing stations were imposed. Both fuselage camber and cross-sectional area distributions were permitted to change during design. The major disadvantage to the use of these functions is the inherent surface waviness produced by repeated use of such functions. Many smoothing operations were required following optimization runs to produce a configuration with reasonable smoothness. Wagner functions were also used on the wing sections but were never used on the fuselage. The Wagner functions are a family of increasingly oscillatory functions that have also been used extensively in airfoil design. The leading and trailing edge regions of the wing were designed by use of polynomial and monomial functions respectively. Twist was attempted but was abandoned because of little performance improvement available from changing the baseline twist.

Cliff, Susan E.↗
DOE OSTI2016

EMAT enhanced dispersion of particles in liquid

Particulate matter is dispersed in a fluid material. A sample including a first material in a fluid state and second material comprising particulate matter are placed into a chamber. The second material is spatially dispersed in the first material utilizing EMAT force. The dispersion process continues until spatial distribution of the second material enables the sample to meet a specified criterion. The chamber and/or the sample is electrically conductive. The EMAT force is generated by placing the chamber coaxially within an induction coil driven by an applied alternating current and placing the chamber and induction coil coaxially within a high field magnetic. The EMAT force is coupled to the sample without physical contact to the sample or to the chamber, by another physical object. Batch and continuous processing are utilized. The chamber may be folded within the bore of the magnet. Acoustic force frequency and/or temperature may be controlled.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Influence of crystallographic orientation and applied magnetic field on domain structure in duplex stainless steel studied using magnetic force microscopy

Highlights: • Ferrite phase in a duplex stainless steel consists of stripe type domains. • Domain contrast decreases with deviation of plane normal from <100>. • Domain width increases with deviation of plane normal from <100>. • Domain alignment with applied field observed along <100> directions. • Grain boundary stray field is a function of misorientation between grains. - Abstract: The paper investigates the local micro-magnetization behavior in duplex stainless steel (DSS) using magnetic force microscopy (MFM). DSS has equal amount of austenite phase in ferrite matrix. The MFM imaging clearly differentiates ferrite phase (ferromagnetic) from the austenite phase (paramagnetic) due to the maze type magnetic domains present in the ferrite phase. The magneto crystalline anisotropic effect on the domain structure is discussed with the support of electron backscatter diffraction (EBSD) measurements. The MFM phase contrast and domain width are correlated with the orientation of surface normal with respect to the easy axis of magnetization (<100>). The influence of external magnetic field (±127 kA/m) application on the domain structure is studied as a function of the grain orientation and the leakage field at the grain boundaries is analyzed based on the mis-orientation between the grains.

36 MATERIALS SCIENCE↗
NASA NTRS2000

The Use of Ferrofluids to Model Materials Processing (MSFC Center Director's Discretionary Fund)

Many crystals grown in space have structural flaws believed to result from convective motions during the growth phase. The character of these instabilities is not well understood but is associated with thermal and solutal density variations near the solidification interface in the presence of residual gravity and g-jitter. To study these instabilities in a separate, controlled space experiment, a concentration gradient would first have to be artificially established in a timely manner as an initial condition. This is generally difficult to accomplish in a microgravity environment because the momentum of the fluid injected into a test cell tends to swirl around and mix in the absence of a restoring force. The use of magnetic fields to control the motion and position of liquids has received recent, growing interest. The possibility of using the force exerted by a non-uniform magnetic field on a ferrofluid to not only achieve fluid manipulation but also to actively control fluid motion makes it an attractive candidate for space applications. This paper describes a technique for quickly establishing a linear or exponential fluid concentration gradient using a magnetic field in place of gravity to stabilize the deployment. Also discussed is a photometric technique for measuring the concentration profile using light attenuation. Although any range of concentrations can be realized, photometric constraints impose some limitations on measurements. Results of the ground-based experiments indicate that the species distribution is within 3 percent of the predicted value.

Leslie, F.↗
NASA NTRS1979

A free-electron laser in a uniform magnetic field

The study shows that a free-electron laser can operate in a uniform, longitudinal magnetic field. The fully relativistic Lorentz force equations are examined and solved order by order in a radiation field strength to obtain analytic expressions for the electron trajectory and energy as functions of initial electron position within a wavelength of light. Analytic expressions for the longitudinal and transverse bunching and for laser gain are found. The bunching of this laser process is compared to the bunching processes involved in (1) a Stanford free-electron laser and (2) a cyclotron maser. The results received can be useful in exploring light amplification in astrophysical magnetic fields, the magnetosphere, and in laboratory devices.

Ride, S. K.↗
NASA NTRS2001

Enhancement of Pool Boiling Heat Transfer and Control of Bubble Motion in Microgravity Using Electric Fields (BCOEL)

The BCOEL project focuses on improving pool boiling heat transfer and bubble control in microgravity by exposing the fluid to electric fields. The electric fields induce a body force that can replace gravity in the low gravity environment, and enhance bubble removal from the heated surface. A better understanding of microgravity effects on boiling with and without electric fields is critical to the proper design of the phase-change-heat-removal equipment for use in spacebased applications. The microgravity experiments will focus on the visualization of bubble formation and shape during boiling. Heat fluxes on the boiling surface will be measured, and, together with the measured driving temperature differences, used to plot boiling curves for different electric field magnitudes. Bubble formation and boiling processes were found to be extremely sensitive to g-jitter. The duration of the experimental run is critical in order to achieve steady state in microgravity experiments. The International Space Station provides conditions suitable for such experiments. The experimental apparatus to be used in the study is described in the paper. The apparatus will be tested in the KC-135 first, and microgravity experiments will be conducted on board of the International Space Station using the Microgravity Science Glovebox as the experimental platform.

Herman, Cila↗
NASA NTRS2001

Enhancement of Pool Boiling Heat Transfer and Control of Bubble Motion in Microgravity Using Electric Fields - BCOEL

The BCOEL project focuses on improving pool boiling heat transfer and bubble control in microgravity by exposing the fluid to electric fields. The electric fields induce a body force that can replace gravity in the low gravity environment, and enhance bubble removal from thc heated surface. A better understanding of microgravity effects on boiling with and without electric fields is critical to the proper design of the phase-change-heat-removal equipment for use in space-based applications. The microgravity experiments will focus on the visualization of bubble formation and shape during boiling. Heat fluxes on the boiling surface will be measured, and, together with the measured driving temperature differences, used to plot boiling curvcs for different electric field magnitudes. Bubble formation and boiling processes were found to be extremely sensitive to g-jitter. The duration of the experimental run is critical in order to achieve steady state in microgravity experiments. The International Space Station provides conditions suitable for such experiments. The experimental appararus to be used in the study is described in the paper. The apparatus will be tested in the KC-135 first, and microgravity experiments will be conducted on board of the International Space Station using the Microgravity Science Glovebox as the experimental platform.

Herman, Cila↗
DOE OSTI2021

Global Microscopic Description of Nucleon-Nucleus Scattering with Quantified Uncertainties

We develop for the first time a microscopic global nucleon-nucleus optical potential with quantified uncertainties suitable for analyzing nuclear reaction experiments at next-generation rare-isotope beam facilities. Within the improved local density approximation and without any adjustable parameters, we begin by computing proton-nucleus and neutron-nucleus optical potentials from a set of five nuclear forces from chiral effective field theory for 1800 target nuclei in the mass range 12 ≤ A ≤ 242 for energies between 0 MeV < E ≲ 150 MeV. We then parameterize a global optical potential for each chiral force that depends smoothly on the projectile energy as well as the target nucleus mass number and isospin asymmetry. Uncertainty bands for elastic scattering observables are generated from a full covariance analysis of the parameters entering in the description of our global optical potential and benchmarked against existing experimental data for stable target nuclei. Since our approach is purely microscopic, we anticipate a similar quality of the model for nucleon scattering on unstable isotopes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Mechanical-force-induced non-local collective ferroelastic switching in epitaxial lead-titanate thin films

Ferroelastic switching in ferroelectric/multiferroic oxides plays a crucial role in determining their dielectric, piezoelectric, and magnetoelectric properties. In thin films of these materials, however, substrate clamping is generally thought to limit the electric-field- or mechanical-force-driven responses to the local scale. Here, we report mechanical-force-induced large-area, non-local, collective ferroelastic domain switching in PbTiO 3 epitaxial thin films by tuning the misfit-strain to be near a phase boundary wherein c/a and a 1 / a 2 nanodomains coexist. Phenomenological models suggest that the collective, c-a-c-a ferroelastic switching arises from the small potential barrier between the degenerate domain structures, and the large anisotropy of a and c domains, which collectively generates much larger response and large-area domain propagation. Large-area, non-local response under small stimuli, unlike traditional local response to external field, provides an opportunity of unique response to local stimuli, which has potential for use in high-sensitivity pressure sensors and switches.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Bias-Modulated ALD of ZnO: Insights into Precursor-Surface Interactions for ZnO Films

Atomic layer deposition (ALD) is widely used to deposit conformal thin films but is often limited in the tunability of the resulting material’s properties. Substrate bias and electric fields alter precursor-surface interactions and provide means to tune material properties. To explore this, we performed zinc oxide (ZnO) ALD using diethylzinc (DEZ) and water on silicon native oxide substrates at 150 °C in a sample holder designed to create a static electrical field by biasing one plate of a parallel plate capacitor-style sample holder during deposition. ZnO films prepared in an electric field/on a biased sample holder were thinner, changed relative crystalline composition, and contained more carbon compared to samples grown in identical sample holders without bias. The thickness was independent of the magnitude of the eletric field between plates, indicating that the primary driver for the change was substrate biasing not the electric field between plates of the parallel plate capacitor-style sample holder. Density functional theory calculations showed enhanced electron migration between dissociatively adsorbed DEZ molecules and the ZnO (002) facet with increasing force from an electric field at the substrate surface, which strengthens the electronic interactions between the surface and the adsorbate. These models offer a compelling explanation for the inhibited growth, changes in the crystallinity, and increase in carbon content of films grown in an electric field/on biased plates.

Jones, Jessica C. (ORCID:0000000174754620)↗
NASA NTRS2008

High Temperature, Permanent Magnet Biased, Fault Tolerant, Homopolar Magnetic Bearing Development

This paper summarizes the development of a magnetic bearing designed to operate at 1,000 F. A novel feature of this high temperature magnetic bearing is its homopolar construction which incorporates state of the art high temperature, 1,000 F, permanent magnets. A second feature is its fault tolerance capability which provides the desired control forces with over one-half of the coils failed. The construction and design methodology of the bearing is outlined and test results are shown. The agreement between a 3D finite element, magnetic field based prediction for force is shown to be in good agreement with predictions at room and high temperature. A 5 axis test rig will be complete soon to provide a means to test the magnetic bearings at high temperature and speed.

Palazzolo, Alan↗