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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Electronic structure with direct diagonalization on a D-wave quantum annealer

Quantum chemistry is regarded to be one of the first disciplines that will be revolutionized by quantum computing. Although universal quantum computers of practical scale may be years away, various approaches are currently being pursued to solve quantum chemistry problems on near-term gate-based quantum computers and quantum annealers by developing the appropriate algorithm and software base. This work implements the general Quantum Annealer Eigensolver (QAE) algorithm to solve the molecular electronic Hamiltonian eigenvalue-eigenvector problem on a D-Wave 2000Q quantum annealer. The approach is based on the matrix formulation, efficiently uses qubit resources based on a power-of-two encoding scheme and is hardware-dominant relying on only one classically optimized parameter. We demonstrate the use of D-Wave hardware for obtaining ground and excited electronic states across a variety of small molecular systems. The approach can be adapted for use by a vast majority of electronic structure methods currently implemented in conventional quantum-chemical packages. The results of this work will encourage further development of software such as qbsolv which has promising applications in emerging quantum information processing hardware and has expectation to address large and complex optimization problems intractable for classical computers.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2021

OC6 Phase Ib: Floating Wind Component Experiment for Difference-Frequency Hydrodynamic Load Validation

A new validation campaign was conducted at the W2 Harold Alfond Ocean Engineering Laboratory at the University of Maine to investigate the hydrodynamic loading on floating offshore wind substructures, with a focus on the low-frequency contributions that tend to drive extreme and fatigue loading in semisubmersible designs. A component-level approach was taken to examine the hydrodynamic loads on individual parts of the semisubmersible in isolation and then in the presence of other members to assess the change in hydrodynamic loading. A variety of wave conditions were investigated, including bichromatic waves, to provide a direct assessment of difference-frequency wave loading. An assessment of the impact of wave uncertainty on the loading was performed, with the goal of enabling validation with this dataset of numerical models with different levels of fidelity. The dataset is openly available for public use and can be downloaded from the U.S. Department of Energy Data Archive and Portal.

17 WIND ENERGY↗
DOE OSTI2021

Scoping study of detecting high harmonic fast waves in NSTX-U hot core plasma directly using beam emission spectroscopy

In this paper, we used radio frequency (RF) full wave simulation to explore the feasibility of generating a density beat oscillation formed by high harmonic fast waves (HHFWs) in the National Spherical Tokamak Experiment-Upgrade (NSTX-U) and of measuring it numerically with 2D beam emission spectroscopy (BES). This oscillation is of interest as it can be used to determine the injected RF fields. We began by computing HHFW fields in NSTX-U under a variety of experimental conditions and antenna configurations with Petra-M, a 3D RF wavefield solver. These fields were then used to evaluate the amplitude of δne,beat/ne0 in the volume of measurement, which we predict to be between 5 × 10−10 and 10−9, although it is highly dependent on plasma parameters. Trends in magnetic field, core temperature, core density, and antenna phasing are presented, and the parameters most suitable to this measurement are identified. Finally, we developed a synthetic BES diagnostic to compare the experimental BES signal against.

Rutherford, Grant (ORCID:0000000163620037)↗
DOE OSTI2022

Coupling Between Alfvén Wave and Kelvin–Helmholtz Waves in the Low Latitude Boundary Layer

The Kelvin–Helmholtz (KH) instability of magnetohydrodynamic surface waves at the low latitude boundary layer is examined using both an eigenfrequency analysis and a time-dependent wave simulation. The analysis includes the effects of sheared flow and Alfvén velocity gradient. When the magnetosheath flows are perpendicular to the ambient magnetic field direction, unstable KH waves that propagate obliquely to the sheared flow direction occur at the sheared flow surface when the Alfvén Mach number is higher than an instability threshold. Including a shear transition layer between the magnetosphere and magnetosheath leads to secondary KH waves (driven by the sheared flow) that are coupled to the resonant surface Alfvén wave. There are remarkable differences between the primary and the secondary KH waves, including wave frequency, the growth rate, and the ratio between the transverse and compressional components. The secondary KH wave energy is concentrated near the shear Alfvén wave frequency at the magnetosheath with a lower frequency than the primary KH waves. Although the growth rate of the secondary KH waves is lower than the primary KH waves, the threshold condition is lower, so it is expected that these types of waves will dominate at a lower Mach number. Because the transverse component of the secondary KH waves is stronger than that of the primary KH waves, more efficient wave energy transfer from the boundary layer to the inner magnetosphere is also predicted.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Coupling between Alfven wave and Kelvin-Helmholtz waves in the low latitude boundary layer

The Kelvin-Helmholtz (KH) instability of magnetohydrodynamic surface waves at the low latitude boundary layer is examined using both an eigenfrequency analysis and a time-dependent wave simulation. The analysis includes the effects of sheared flow and Alfven velocity gradient. When the magnetosheath flows are perpendicular to the ambient magnetic field direction, unstable KH waves that propagate obliquely to the sheared flow direction occur at the sheared flow surface when the Alfv\'en Mach number is higher than an instability threshold. Including a shear transition layer between the magnetosphere and magnetosheath leads to secondary KH waves (driven by the sheared flow) that are coupled to the resonant surface Alfven wave. There are remarkable differences between the primary and the secondary KH waves including wave frequency, the growth rate, and the ratio between transverse and the compressional component. The secondary KH wave energy is concentrated near the shear Alfven wave frequency at the magnetosheath with a lower frequency than the primary KH waves. Although the growth rate of the secondary KH waves is lower than the primary KH waves, the threshold condition is lower, so it is expected that these types of waves will dominate at lower Mach number. Because the transverse component of the secondary KH waves is stronger than the primary KH waves, more efficient wave energy transfer from the boundary layer to the inner magnetosphere is also predicted.

Alfven wave↗
DOE OSTI2020

Non-standing spin-waves in confined micrometer-sized ferromagnetic structures under uniform excitation

A non-standing characteristic of directly imaged spin-waves in confined micrometer-sized ultrathin Permalloy (Ni 80 Fe 20 ) structures is reported along with evidence of the possibility to alter the observed state by modifications to the sample geometry. Using micromagnetic simulations, the presence of the spin-wave modes excited in the Permalloy stripes along with the quasi-uniform modes was observed. The predicted spin-waves were imaged in direct space using time resolved scanning transmission x-ray microscopy, combined with a ferromagnetic resonance excitation scheme (STXM-FMR). STXM-FMR measurements revealed a non-standing characteristic of the spin-waves. Also, it was shown by micromagnetic simulations and confirmed using STXM-FMR results that the observed characteristic of the spin-waves can be influenced by the local magnetic fields in different sample geometries.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Different responses of the Rayleigh–Taylor type and resistive drift wave instabilities to the velocity shear

The effects of velocity shear on the unstable modes driven by the effective gravity (Rayleigh–Taylor and interchange) and resistive drift wave instabilities for inhomogeneous equilibrium fluid/plasma density are analyzed for the localized eigenmode problems. It is shown that the effect of the velocity shear drastically depends on the type of instability. Whereas the velocity shear can significantly suppress both Rayleigh–Taylor and interchange instabilities, it has only a weak impact on the growth rate of the resistive drift wave. This is directly related to the physical nature of these instabilities. For the Rayleigh–Taylor and interchange instabilities, the shear flow tilts the eddies of the stream functions, while for the resistive drift wave instability the shear flow simply shifts the eddies in the radial direction with no tilting. However, for a large velocity shear, the eigenmode solutions for resistive drift waves cease to exist.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Ocean Wave Energy Harvester with Oak Ridge Converter

Oceans can provide great potential for the American energy dominance. There is significant potential to utilize marine energy resources. In the United States, the total amount of marine energy available is equivalent to about 57% of the country's total power generation in 2019. Even if a fraction of this technical potential is harnessed, marine energy technologies could play a crucial role in fulfilling the nation's energy requirements. Marine energy resources are spread out geographically, and because more than 50% of the United States' population resides within 50 miles of the coastline, they are well-positioned to power local communities. These resources are also very dependable, making them a viable option for contributing to a consistent, trustworthy energy grid. Due to their predictable daily and seasonal patterns, marine energy resources can be integrated into our energy generation portfolio. On the other hand, ocean environment presents many challenges for cost-effective renewable energy conversion, including optimal control of ocean wave energy. This report presents a novel cost-effective energy conversion technique for ocean wave energy harvesters. The proposed system is simulated by using the Oak Ridge Converter to directly interface ocean wave energy source with the utility grid. The system description and simulation results are presented in detail. The results show that the proposed system is a cost effective and promising technology to reduce the infrastructure cost for ocean wave energy harvesters.

Sutton, Elizabeth [ORNL] (ORCID:0009000078885935)↗
DOE OSTI2026

Real-space atomic dynamics in liquid gallium studied by inelastic neutron scattering

Gallium is a prototypical liquid metal and has gained renewed attention because of its unique properties. Characterizing and elucidating its atomic dynamics remains elusive despite numerous studies, primarily because of the challenges in quantifying atomic-scale dynamics in liquids. Recent developments in inelastic neutron scattering enable us to measure the Van Hove correlation function that describes the real-space motion of liquid atoms. Here, in this work, we use this approach to reveal the dynamics in gallium liquids and find the co-existence of two dynamical medium-range orders (MROs), which have a dynamical behavior distinct from that of the short-range order (SRO). We propose that these MROs are driven by global forces in the form of two density waves, as a direct consequence of the underlying competition between ionic core repulsion and valence electron cohesion. We suggest that the density wave approach is not only applicable to other metallic liquids exhibiting similar structural anomalies, but also offers a promising direction for elucidating the dynamics of complex liquids and glasses by linking electronic-state fluctuations to atomic dynamics.

Hua, Chengyun [Oak Ridge National Laboratory (ORNL↗
DOE OSTI2021

On the Symmetry of Blast Waves

This paper presents a brief historical review of G. I. Taylor’s solution of the point blast wave problem which was applied to the Trinity test of the first atomic bomb. Lie group symmetry techniques (also referred to throughout this paper as geometric techniques) are used to derive Taylor’s famous two-fifths law that relates the position of a blast wave to the time after the explosion and the total energy released. The theory of exterior differential systems is combined with the method of characteristics to demonstrate that the solution of the blast wave problem is directly related to the basic relationships that exist between the symmetry (or geometry) and the physics of wave propagation through the equations of motion. The point blast wave model is cast in terms of two exterior differential systems, and both systems are shown to be integrable with local solutions for the velocity, pressure, and density along curves in space and time behind the blast wave. This work is dedicated to the memory of Professor Roy Axford, who introduced many of his students to the topic of symmetry analysis of differential equations.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2021

Wave energy resource characterization employing joint distributions in frequency-direction-time domain

Joint and marginal distributions in the frequency, direction, and time domain are employed to demonstrate their value for wave energy resource characterization when full spectra are available. Insights gained through analysis of these distributions support wave energy converter concept design, operation and maintenance. Spatial trends in the wave energy resource and contributing wave energy systems along the continental shelf of the West Coast of the United States are investigated using the most recent two-dimensional wave spectra measurements at four buoys over an eleven year period (2008 to 2018). Resource hot spots and dominant resolved energy resource bands in the frequency-direction-time domain are delineated. Resource attributes, including frequency and directional spreading, and seasonal variability, are characterized using joint distributions and marginal distributions of wave power spectra. North Pacific westerly swells in the winter season, augmented by Aleutian low-pressure southwesterly swells, are the principal suppliers of the dominant resource and main drivers influencing resource attributes. In conclusion, the modification of these systems southward, especially the North Pacific westerly swells, explains the observed spatial resource trends. The dominant resource wave period shifts two seconds to higher wave periods, thirty degrees in the dominant direction band to a more northward orientation, and forward by one month.

16 TIDAL AND WAVE POWER↗
DOE OSTI2020

Magnetic reconnection and kinetic waves generated in the Earth's quasi-parallel bow shock

Magnetic reconnection in quasi-parallel shocks, relevant to the Earth’s bow shock, is studied by means of two-dimensional full particle-in-cell simulations. As the Alfvénic Mach number increases, the propagation direction of the waves excited in the transition region changes, and the shock becomes more turbulent with more reconnection sites. In the higher Mach number shock, abundant electron-only reconnection sites are generated with scales on the order of the ion skin depth or less. Non-reconnecting current sheets can also generate electron jets and energy dissipation can occur there as well. However, non-reconnecting current sheets with the magnetic field reversal typically show a smaller energy dissipation rate than reconnecting current sheets. In the shock transition region, two types of waves are responsible for driving reconnection: one has a wavelength around three ion skin depths (d i ), and the other has a wavelength less than 1 d i . Here, electron and ion distribution functions show that in regions where the former type of waves is excited, there are two ion beams and a single-peaked electron distribution. In contrast, in regions where the latter type of waves is excited, there are multiple electron and ion beams. The waves propagating obliquely to the magnetic field bend the magnetic field lines, and magnetic reconnection occurs where oppositely directed field lines come into contact.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Anisotropic magnetic excitations of a frustrated bilinear-biquadratic spin model: Implications for spin waves of detwinned iron pnictides

Elucidating the nature of spin excitations is important to understanding the mechanism of superconductivity in the iron pnictides. Motivated by recent inelastic neutron scattering measurements in the nearly 100% detwinned BaFe 2 As 2 , we study the spin dynamics of an $\textit{S}$ = 1 frustrated bilinear-biquadratic Heisenberg model in the antiferromagnetic phase with wave vector (π, 0). The biquadratic interactions are treated in a dynamical way using a flavor-wave theory in an $\textit{SU}$(3) representation. Besides the dipolar spin wave (magnon) excitations, the biquadratic interactions give rise to quadrupolar excitations at high energies. In this work, we find that the quadrupolar wave significantly influences, in an energy dependent way, the anisotropy between the spin excitation spectra along the (π, 0) and (0, π) directions in the wave vector space. Our theoretical results capture the essential behavior of the spin dynamics measured in the antiferromagnetic phase of the detwinned BaFe 2 As 2 . More generally, our results underscore the importance of electron correlation effects for the microscopic physics of the iron pnictides.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

The effect of a transducer’s spatial averaging on an elastodynamic guided wave’s wavenumber spectrum

Elastodynamic guided waves propagate in an elastic solid which makes it difficult, if not impractical, to place a receiving transducer in the direct path of the propagating wave (as one would for an acoustic wave in a fluid medium). Thus, to account for this, receiving transducers are often placed on the surface of the solid waveguide such that the transducer surface is parallel to the wave propagation direction. This transducer orientation introduces spatial averaging, which causes the received signal to have an altered signal amplitude and mode bias. We investigate both of these effects and present a simple model from which we derive a scaling-ratio expression that describes the effects of spatial averaging. Furthermore, we then test its performance using finite-element simulations that incorporate “real-world” assumptions (e.g., transient waves, piezoelectric effects, etc.). The results from the simulations demonstrate that the scaling-ratio can characterize the effects resulting from spatial averaging. The scaling-ratio expression will be particularly useful when designing experiments involving high frequency (small wavelength) guided waves. Lastly, the proposed scaling-ratio expression could be applied to other sensing methods, like Laser Doppler Vibrometry (LDV) or piezoelectric waveguides with inter-digitated transducers, because of its generality. However, the authors are careful to note that the scaling-ratio expression is not intended as a replacement of multi-physics analysis or good experimental design, and the effects of spatial averaging should be avoided whenever possible.

2DFFT↗
DOE OSTI2026

Studies of whistler propagation along a plasma density gradient that is parallel to the magnetic field

Low frequency plasma wave generation in space is important for both scientific and practical applications. One of the most promising techniques for doing this is to directly inject whistler waves into the space environment from an antenna onboard one or more satellites. This technique has been discussed for years, but there are still open questions about the best way to generate plasma waves. So far, most theoretical [Kondrat92], lab based [Pribyl2010, Stenzel2016] and space-based experiments [DSX] have focused on studying the generation of whistler waves from an electric dipole antenna. However, a dipole antenna is very inefficient because it puts a lot of energy in waves that are not effective for most applications. Theoretical [Kondrat92] and lab experimental [Stenzel2016] results indicate that a loop antenna is much more efficient at generating whistler waves than a dipole antenna. A satellite experiment will need to be developed to demonstrate that whistler waves can be generated from a loop antenna in the space environment. The challenge is that to efficiently transmit whistler modes in the natural plasma environment of space, the loop antenna will have to be very large. For example, at L=2 (one earth radius away from the surface of the earth) a loop antenna would need a radius on the order of ~200 m to radiate efficiently, as shown in fig. 1, left. The antenna size and complexity would require a prohibitively large and expensive satellite mission. Our proposed innovation is to exploit the fact that the characteristic wavelength of whistler waves decreases in more dense plasma, which reduces the size needed for an antenna to radiate efficiently. Fortunately, a technique already exists for enhancing the local plasma density in space, called a plasma contactor [Kovaleski2001]. A plasma contactor can be used to create a local environment where the plasma density is enhanced around the satellite, which in turn reduces the size of an antenna that is needed to radiate efficiently (Fig. 1, right).

42 ENGINEERING↗
DOE OSTI2024

Direct observation of entangled electronic-nuclear wave packets

We present momentum resolved covariance measurements of entangled electronic-nuclear wave packets created and probed with octave spanning phaselocked ultrafast pulses. We launch vibrational wave packets on multiple electronic states via multiphoton absorption, and probe these wave packets via strong field double ionization using a second phaselocked pulse. Momentum resolved covariance mapping of the fragment ions highlights the nuclear motion, while measurements of the yield as a function of the relative phase between pump and probe pulses highlight the electronic coherence. The combined measurements allow us to directly visualize the entanglement between the electronic and nuclear degrees of freedom and follow the evolution of the complete wavefunction. Published by the American Physical Society 2024

Moğol, Gönenç↗
DOE OSTI2024

Weak magnetohydrodynamic turbulence theory revisited

Two recent papers, P. H. Yoon and G. Choe, Phys. Plasmas 28, 082306 (2021) and Yoon et al., Phys. Plasmas 29, 112303 (2022), utilized in the derivation of the kinetic equation for the intensity of turbulent fluctuations the assumption that the wave spectra are isotropic, that is, the ensemble-averaged magnetic field tensorial fluctuation intensity is given by the isotropic diagonal form, ⟨δBiδBj⟩k=⟨δB2⟩kδij. However, it is more appropriate to describe the incompressible magnetohydrodynamic turbulence involving shear Alfvénic waves by modeling the turbulence spectrum as being anisotropic. That is, the tensorial fluctuation intensity should be different in diagonal elements across and along the direction of the wave vector, ⟨δBiδBj⟩k=12 ⟨δB⊥2⟩k(δij−kikj/k2)+⟨δB∥2⟩k(kikj/k2). In the present paper, we thus reformulate the weak magnetohydrodynamic turbulence theory under the assumption of anisotropy and work out the form of nonlinear wave kinetic equation.

Physics↗