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At least 1,765 records · Page 98
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Alpha particle driven Alfvénic instabilities in ITER post-disruption plasmas

Fusion-born alpha particles in ITER disruption simulations are investigated as a possible drive of Alfvénic instabilities. The ability of these waves to expel runaway electron (RE) seed particles is explored in the pursuit of a passive, inherent RE mitigation scenario. The spatiotemporal evolution of the alpha particle distribution during the disruption is calculated using the linearized Fokker–Planck solver CODION coupled to a fluid disruption simulation. These simulations are done in the limit of no alpha particle transport during the thermal quench, which can be seen as a most pessimistic situation where there is also no RE seed transport. Under these assumptions, the radial anisotropy of the resulting alpha population provides free energy to drive Alfvénic modes during the quench phase of the disruption. We use the linear gyrokinetic magnetohydrodynamic code LIGKA to calculate the Alfvén spectrum and find that the equilibrium is capable of sustaining a wide range of modes. The self-consistent evolution of the mode amplitudes and the alpha distribution is calculated utilizing the wave-particle interaction tool HAGIS. Intermediate mode number (n = 7–15, 22–26) toroidal Alfvén eigenmodes are shown to saturate at an amplitude of up to δB/B ≈ 0.1% in the spatial regimes crucial for RE seed formation. We find that the mode amplitudes are predicted to be sufficiently large to permit the possibility of significant radial transport of REs.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2011

Emergent structure in a dipolar Bose gas in a one-dimensional lattice

We consider an ultracold dipolar Bose gas in a one-dimensional lattice. For a sufficiently large lattice recoil energy, such a system becomes a series of nonoverlapping Bose-Einstein condensates that interact via the long-range dipole-dipole interaction (ddi). We model this system via a coupled set of nonlocal Gross-Pitaevskii equations (GPEs) for lattices of both infinite and finite extent. We find significantly modified stability properties in the lattice due to the softening of a discrete roton-like mode, as well as ''islands'' in parameter space where biconcave densities are predicted to exist and that only exist in the presence of the other condensates on the lattice. We solve for the elementary excitations of the system to check the dynamical stability of these solutions and to uncover the nature of their collapse. By solving a coupled set of GPEs exactly on a full numeric grid, we show that this emergent biconcave structure can be realized in a finite lattice with atomic {sup 52}Cr.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Holographic thermalization in a quark confining background

We study holographic thermalization of a strongly coupled theory inspired by two colliding shock waves in a vacuum confining background. Holographic thermalization means a black hole formation, in fact, a trapped surface formation. As the vacuum confining background, we considered the well-know bottom-up AdS/QCD model that provides the Cornell potential and reproduces the QCD β-function. We perturb the vacuum background by colliding domain shock waves that are assumed to be holographically dual to heavy ions collisions. Our main physical assumption is that we can make a restriction on the time of trapped surface formation, which results in a natural limitation on the size of the domain where the trapped surface is produced. This limits the intermediate domain where the main part of the entropy is produced. In this domain, we can use an intermediate vacuum background as an approximation to the full confining background. We find that the dependence of the multiplicity on energy for the intermediate background has an asymptotic expansion whose first term depends on energy as E{sup 1/3}, which is very similar to the experimental dependence of particle multiplicities on the colliding ion energy obtained from the RHIC and LHC. However, this first term, at the energies where the approximation of the confining metric by the intermediate background works, does not saturate the exact answer, and we have to take the nonleading terms into account.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

The impacts of oceanic deep temperature perturbations in the North Atlantic on decadal climate variability and predictability

Decadal climate predictability in the North Atlantic is largely related to ocean low frequency variability, whose sensitivity to initial conditions is not very well understood. Recently, three-dimensional oceanic temperature anomalies optimally perturbing the North Atlantic Mean Temperature (NAMT) have been computed via an optimization procedure using a linear adjoint to a realistic ocean general circulation model. The spatial pattern of the identified perturbations, localized in the North Atlantic, has the largest magnitude between 1000 and 4000 m depth. In the present study, the impacts of these perturbations on NAMT, on the Atlantic meridional overturning circulation (AMOC), and on climate in general are investigated in a global coupled model that uses the same ocean model as was used to compute the three-dimensional optimal perturbations. In the coupled model, these perturbations induce AMOC and NAMT anomalies peaking after 5 and 10 years, respectively, generally consistent with the ocean-only linear predictions. To further understand their impact, their magnitude was varied in a broad range. For initial perturbations with a magnitude comparable to the internal variability of the coupled model, the model response exhibits a strong signature in sea surface temperature and precipitation over North America and the Sahel region. The existence and impacts of these ocean perturbations have important implications for decadal prediction: they can be seen either as a source of predictability or uncertainty, depending on whether the current observing system can detect them or not. In fact, comparing the magnitude of the imposed perturbations with the uncertainty of available ocean observations such as Argo data or ocean state estimates suggests that only the largest perturbations used in this study could be detectable. This highlights the importance for decadal climate prediction of accurate ocean density initialisation in the North Atlantic at intermediate and greater depths.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Importance of Unimolecular HO 2 Elimination in the Heterogeneous OH Reaction of Highly Oxygenated Tartaric Acid Aerosol

Oxygenated organic molecules are abundant in atmospheric aerosols and are transformed by oxidation reactions near the aerosol surface by gas-phase oxidants such as hydroxyl (OH) radicals. To gain better insights into how the structure of an organic molecule, particularly in the presence of hydroxyl groups, controls the heterogeneous reaction mechanisms of oxygenated organic compounds, this paper investigates the OH-radical initiated oxidation of aqueous tartaric acid (C 4 H 6 O 6 ) droplets using an aerosol flow tube reactor. The molecular composition of the aerosols before and after reaction is characterized by a soft atmospheric pressure ionization source (Direct Analysis in Real Time) coupled with a high-resolution mass spectrometer. The aerosol mass spectra reveal that four major reaction products are formed: a single C 4 functionalization product (C 4 H 4 O 6 ) and three C 3 fragmentation products (C 3 H 4 O 4 , C 3 H 2 O 4 , and C 3 H 2 O 5 ). The C 4 functionalization product does not appear to originate from peroxy radical self-reactions but instead forms via an α-hydroxylperoxy radical produced by a hydrogen atom abstraction by OH at the tertiary carbon site. The proximity of a hydroxyl group to peroxy group enhances the unimolecular HO 2 elimination from the α-hydroxylperoxy intermediate. This alcohol-to-ketone conversion yields 2-hydroxy-3-oxosuccinic acid (C 4 H 4 O 6 ), the major reaction product. While in general, C–C bond scission reactions are expected to dominate the chemistry of organic compounds with high average carbon oxidation states (OS C ), our results show that molecular structure can play a larger role in the heterogeneous transformation of tartaric acid (OS C = 1.5). Finally, these results are also compared with two structurally related dicarboxylic acids (succinic acid and 2,3-dimethylsuccinic acid) to elucidate how the identity and location of functional groups (methyl and hydroxyl groups) alter heterogeneous reaction mechanisms.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Black hole hair from scalar dark matter

In this report we show that a black hole surrounded by scalar dark matter develops scalar hair. This is the generalization of a phenomenon pointed out by Jacobson [1], that a minimally coupled scalar with a non-trivial time dependence far away from the black hole would endow the black hole with hair. In our case, the time dependence arises from the oscillation of a scalar field with a non-zero mass. We systematically explore the scalar profile around the black hole for different scalar masses. In the small mass limit, the scalar field has a 1/r component at large radius r, consistent with Jacobson's result. In the large mass limit (with the Compton wavelength of order of the horizon or smaller), the scalar field has a 1/r 3/4 profile yielding a pile-up close to the horizon, while distinctive nodes occur for intermediate masses. Thus, the dark matter profile around a black hole, while challenging to measure, contains information about the dark matter particle mass. As an application, we consider the case of the supermassive black hole at the center of M87, recently imaged by the Event Horizon Telescope. Its horizon size is roughly the Compton wavelength of a scalar particle of mass 10 -20 eV. We consider the implications of the expected scalar pile-up close to the horizon, for fuzzy dark matter at a mass of 10 -20 eV or below.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1976

Fabrication process development of SiC/superalloy composite sheet for exhaust system components

A chemical compatibility study was conducted between SiC filament and the following P/M matrix alloys: Waspaloy, Hastelloy-X, NiCrAlY, Ha-188, S-57, FeCrAlY, and Incoloy 800. None of the couples demonstrated sufficient chemical compatibility to withstand the minimum HIP consolidation temperatures (996 C) or intended application temperature of the composite (982 C). However, Waspaloy, Haynes 188, and Hastelloy-X were the least reactive with SiC of the candidate alloys. Chemical vapor deposited tungsten was shown to be an effective diffusion barrier between the superalloy matrix and SiC filament providing a defect-free coating of sufficient thickness. However, the coating breaks down when the tungsten is converted into intermetallic compounds by interdiffusion with matrix constituents. Waspaloy was demonstrated to be the most effective matrix alloy candidate in contact with the CVD tungsten barrier because of its relatively low growth rate constant of the intermediate compound and the lack of formation of Kirkendall voids at the matrix-barrier interface. Fabrication methods were developed for producing panels of uniaxial and angle ply composites utilizing CVD tungsten coated filament.

Cornie, J. A.↗
DOE OSTI2016

Direct observation of light-driven, concerted electron–proton transfer

Significance Concerted proton-coupled electron transfer (EPT) reactions in which both electrons and protons transfer in tandem are at the heart of many chemical and biological conversions including photosystem II. We report here the direct observation of absorption bands arising from photoEPT transitions, in this case, in H-bonded complexes between N -methyl-4,4′-bipyridinium cation and biologically relevant donors including tyrosine. The importance of these observations follows from the earlier experimental observations by Taube and coworkers on intervalence transfer in mixed-valence complexes. The observation of these photoEPT transitions and the appearance of reactive radical products also points to a possible, if inefficient, role in DNA photodamage and, possibly, in the formation of reactive oxygen intermediates.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

The Curious Case of Pu + : Insight on 5f Orbital Activity from Inductively Coupled Plasma Tandem Mass Spectrometry (ICP-MS/MS) Reactions

A comprehensive understanding of when and how 5f orbitals participate in complex chemical bonding is important for a variety of applications. The actinides are unique in that they possess 5f orbitals and can access high oxidation states, which make them attractive for use in catalysis. Fundamental studies of actinide–ligand interactions offer a mechanism to examine the activation of the 5f orbitals so that the selectivity of 5f orbitals can be assessed. A previous study examined the reaction of Pu + + CO 2 and determined that the reaction efficiency is restricted by a barrier, namely, promotion from the Pu + ground-state configuration, 5f 6 7s, to a reactive-state configuration, 5f 5 6d 2 . Here, the present study illustrates the benefit of activation of Pu’s 5f orbitals when studying the reaction of Pu + + NO. In this reaction, PuO + forms in an exothermic, barrierless process. The 5f orbitals can and do participate in forming a linear intermediate, [N-Pu-O] + , and this drives the exothermic reaction. Understanding the conditions under which 5f orbitals are active in chemical bonding is the key to exploiting the actinides’ selective catalytic capabilities.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Three-stage decoherence dynamics of an electron spin qubit in an optically active quantum dot

We report the control of solid-state qubits requires a detailed understanding of the decoherence mechanisms. Despite considerable progress in uncovering the qubit dynamics in strong magnetic fields, decoherence at very low magnetic fields remains puzzling, and the role of quadrupole coupling of nuclear spins is poorly understood. For spin qubits in semiconductor quantum dots, phenomenological models of decoherence include two basic types of spin relaxation: fast dephasing due to static but randomly distributed hyperfine fields (~2 ns) and a much slower process (>1 μs) of irreversible monotonic relaxation due either to nuclear spin co-flips or other complex many-body interaction effects. Here we show that this is an oversimplification; the spin qubit relaxation is determined by three rather than two distinct stages. Finally, the additional stage corresponds to the effect of coherent precession processes that occur in the nuclear spin bath itself, leading to a relatively fast but incomplete non-monotonic relaxation at intermediate timescales (~750 ns).

36 MATERIALS SCIENCE↗
DOE OSTI2010

Spin identification of graviton resonances in the process pp {sup {yields}}e{sup +}e{sup -} + X at the Large Hadron Collider (LHC)

Prospects for discovering heavy graviton resonances in decays to an electron-positron pair and for identifying the nature of these resonances in the ATLAS experiment at the Large Hadron Collider (LHC) are investigated. Gravitons in the Randall-Sundrum model, which features extra spatial dimensions, are considered by way of example. A comparative analysis of effects of new different-spin heavy resonances, scalar [supersymmetric neutrino (sneutrino)], vector (new gauge Z' boson), and tensor (graviton) ones, is performed in order to identify the graviton spin. An identification of gravitons is performed by using the integrated center-edge asymmetry. For LHC, the graviton discovery (identification) reach is found to be 2.1 TeV (1.2 TeV) and 3.9 TeV (2.9 TeV) at a confidence level of 5{delta} (95%) for the graviton coupling constants of k/bar M {sub Pl} = 0.01 and 0.1, respectively. This analysis is the most general, since, for the first time, it takes into account the possible existence of scalar resonances, which affects substantially quantitative estimates of the identification reach.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

The Impact of Parameterized Lateral Mixing on the Antarctic Circumpolar Current in a Coupled Climate Model

This study examines the impact of changing the lateral diffusion coefficient ARedi on the transport of the Antarctic Circumpolar Current (ACC). The lateral diffusion coefficient ARedi is poorly constrained, with values ranging across an order of magnitude in climate models. The ACC is difficult to accurately simulate, and there is a large spread in eastward transport in the Southern Ocean (SO) in these models. This paper examines how much of that spread can be attributed to different eddy parameterization coefficients. A coarse-resolution, fully coupled model suite was run with A Redi = 400, 800, 1200, and 2400 m 2 s -1 . Additionally, two simulations were run with two-dimensional representations of the mixing coefficient based on satellite altimetry. Relative to the 400 m 2 s -1 case, the 2400 m 2 s -1 case exhibits 1) an 11% decrease in average wind stress from 50° to 65°S, 2) a 20% decrease in zonally averaged eastward transport in the SO, and 3) a 14% weaker transport through the Drake Passage. The decrease in transport is well explained by changes in the thermal current shear, largely due to increases in ocean density occurring on the northern side of the ACC. In intermediate waters these increases are associated with changes in the formation of intermediate waters in the North Pacific. We hypothesize that the deep increases are associated with changes in the wind stress curl allowing Antarctic Bottom Water to escape and flow northward.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Photo-induced water oxidation at the aqueous GaN (101¯0) interface: Deprotonation kinetics of the first proton-coupled electron-transfer step

Photoeclectrochemical water splitting plays a key role in a promising path to the carbon-neutral generation of solar fuels. Wurzite GaN and its alloys ( e.g. , GaN/ZnO and InGaN) are demonstrated photocatalysts for water oxidation, and they can drive the overall water splitting reaction when coupled with co-catalysts for proton reduction. In the present work, we investigate the water oxidation mechanism on the prototypical GaN (101¯0) surface using a combined ab initio molecular dynamics and molecular cluster model approach taking into account the role of water dissociation and hydrogen bonding within the first solvation shell of the hydroxylated surface. The investigation of free-energy changes for the four proton-coupled electron-transfer (PCET) steps of the water oxidation mechanism shows that the first PCET step for the conversion of –Ga-OH to –Ga-O˙⁻ requires the highest energy input. We further examine the sequential PCETs, with the proton transfer (PT) following the electron transfer (ET), and find that photo-generated holes localize on surface –NH sites is thermodynamically more favorable than –OH sites. However, proton transfer from –OH sites with subsequent localization of holes on oxygen atoms is kinetically favored owing to hydrogen bonding interactions at the GaN (101¯0)–water interface. We find that the deprotonation of surface –OH sites is the limiting factor for the generation of reactive oxyl radical ion intermediates and consequently for water oxidation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Bioprocess development for muconic acid production from aromatic compounds and lignin

Muconic acid (MA) is a bio-based platform chemical that can be converted into the commodity petrochemical building blocks adipic acid or terephthalic acid, or used in emerging, performance-advantaged materials. MA is a metabolic intermediate in the ß-ketoadipate pathway, and can be produced from carbohydrates or other traditional carbon sources via the shikimate pathway. MA can also be produced from lignin-derived aromatic compounds with high atom efficiency through aromatic-catabolic pathways. Metabolic engineering efforts to date have developed efficient muconic acid-producing strains of the aromatic-catabolic microbe Pseudomonas putida KT2440, but the titers, productivities, and yields from aromatic compounds in most cases remain below the thresholds needed for industrially-relevant bioreactor cultivations. To that end, this work presents further process and host development towards improving MA titers, yields, and productivities, using the hydroxycinnamic acids, pcoumaric acid and ferulic acid, as model aromatic compounds. Coupling strain engineering and bioprocess development enabled the discovery of new bottlenecks in P. putida that hinder MA production from these compounds. A combination of gene overexpression and removal of a global catabolic regulator resulted in highyielding strains (100% molar yield). Maximum MA titers of 50 g/L, which is near the lethal toxicity limit in this bacterium, and productivities over 0.5 g/L/h were achieved in separate process configurations. Additionally, a high-pH feeding strategy, which could potentially reduce the salt load and enable higher titers by decreasing product dilution, was tested with model compounds and lignin-rich streams from corn stover and a complete conversion of the primary monomeric aromatic compounds to MA was demonstrated, obtaining a titer of 4 g/L. Overall, this study presents a step forward for the production of value-added chemicals from lignin and highlights critical needs for further strain improvement and bioprocess development that can be applied in the biological valorization of lignin.

09 BIOMASS FUELS↗
DOE OSTI2017

Magnetism and the spin state in cubic perovskite CaCo O 3 synthesized under high pressure

Cubic SrCo O 3 with an intermediate spin state can only be stabilized by high pressure and high temperature (HPHT) treatment. It is metallic and ferromagnetic with the highest Curie temperature of the transition-metal perovskites. The chemical substitution by Ca on Sr sites would normally lower crystal symmetry from cubic to orthorhombic as seen in the perovskite family of Ca M O 3 ( M = M 4 + of transition metals, G e 4 + , S n 4 + , and Z r 4 + ) at room temperature. This structural change narrows the bandwidth, so as to further enhance the Curie temperature as the crossover to the localized electronic state is approached. Here, we report a successful synthesis of the perovskite CaCo O 3 with a HPHT treatment. Surprisingly, CaCo O 3 crystallizes in a simple cubic structure that remains stable down to 20 K, the lowest temperature in the structural study. The new perovskite has been thoroughly characterized by a suite of measurements including transport, magnetization, specific heat, thermal conductivity, and thermoelectric power. Furthermore, metallic CaCo O 3 undergoes two successive magnetic transitions at 86 K and 54 K as temperature decreases. The magnetization at 5 K is compatible with the intermediate spin state t 4 e 1 of C o 4 + at the octahedral site. The thermal expansion of the Co-O bond length indicates that the population of high spin state t 3 e 2 increases for T > 100 K . The shortest Co-O bond length in cubic CaCo O 3 is responsible for delocalizing electrons in the π * -band and itinerant-electron ferromagnetism at T < 54 K . In our comprehensive comparison between SrCo O 3 and CaCo O 3 and the justification of their physical properties by first-principles calculation were made in this report. Partially filled π * and σ * bands would make CaCo O 3 suitable to study the Hund's coupling effect in a metal.

36 MATERIALS SCIENCE↗
DOE OSTI2017

iPTF 16asu: A Luminous, Rapidly Evolving, and High-velocity Supernova

Wide-field surveys are discovering a growing number of rare transients whose physical origin is not yet well understood. We present optical and UV data and analysis of intermediate Palomar Transient Factory (iPTF) 16asu, a luminous, rapidly evolving, high-velocity, stripped-envelope supernova (SN). With a rest-frame rise time of just four days and a peak absolute magnitude of M g = -20.4 mag, the light curve of iPTF 16asu is faster and more luminous than that of previous rapid transients. The spectra of iPTF 16asu show a featureless blue continuum near peak that develops into an SN Ic-BL spectrum on the decline. We show that while the late-time light curve could plausibly be powered by 56 Ni decay, the early emission requires a different energy source. Nondetections in the X-ray and radio strongly constrain the energy coupled to relativistic ejecta to be at most comparable to the class of low-luminosity gamma-ray bursts (GRBs). We suggest that the early emission may have been powered by either a rapidly spinning-down magnetar or by shock breakout in an extended envelope of a very energetic explosion. In either scenario a central engine is required, making iPTF 16asu an intriguing transition object between superluminous SNe, SNe Ic-BL, and low-luminosity GRBs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

On variations of pre-supernova model properties

We explore the variation in single-star 15–30 M{sub ⊙}, nonrotating, solar metallicity, pre-supernova MESA models that is due to changes in the number of isotopes in a fully coupled nuclear reaction network and adjustments in the mass resolution. Within this two-dimensional plane, we quantitatively detail the range of core masses at various stages of evolution, mass locations of the main nuclear burning shells, electron fraction profiles, mass fraction profiles, burning lifetimes, stellar lifetimes, and compactness parameter at core collapse for models with and without mass-loss. Up to carbon burning, we generally find that mass resolution has a larger impact on the variations than the number of isotopes, while the number of isotopes plays a more significant role in determining the span of the variations for neon, oxygen, and silicon burning. Choice of mass resolution dominates the variations in the structure of the intermediate convection zone and secondary convection zone during core and shell hydrogen burning, respectively, where we find that a minimum mass resolution of ≈0.01 M{sub ⊙} is necessary to achieve convergence in the helium core mass at the ≈5% level. On the other hand, at the onset of core collapse, we find ≈30% variations in the central electron fraction and mass locations of the main nuclear burning shells, a minimum of ≈127 isotopes is needed to attain convergence of these values at the ≈10% level.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Mesoscale to Microscale Coupling for a Wind Ramp Case over Complex Terrain

Within the wind energy community, it has become increasingly important to simulate realistic weather events at high fidelity in order to improve wind turbine design, wind farm efficiency, and power forecasting. One of the major difficulties in simulating atmospheric events with numerical models at high fidelity is in accurately transitioning from the mesoscale to the microscale. The mesoscale flow, when input into the large-eddy simulation (LES) domain, will be free of resolved turbulence; needing sufficient time and space (known as fetch) for resolved-scale turbulence to develop. In order to reduce this fetch, several methods exist in which the temperature field, wind field, or both, are stochastically perturbed in order to accelerate the generation of turbulence. However, for cases involving complex terrain, it remains unclear if these perturbation processes are necessary, and if the interaction of the flow over the terrain, alone, is sufficient to generate adequate turbulence. In this study, a wind ramp event observed at the National Wind Technology Center (NWTC) outside of Boulder, CO is simulated first with a mesoscale model and then, using the simulated mesoscale solution as initial and boundary conditions, within a microscale LES solver. The mesoscale solution generated by the Weather Research and Forecasting (WRF) model accurately captures the wind ramp event with only a slight temporal shift and a small temperature bias when compared to the meteorological towers in the NWTC site. This information is then taken as the initial and boundary conditions within the Simulator for Wind Farm Applications (SOWFA) microscale LES model with varying terrain inputs. These inputs include the high-resolution (roughly 30 m grid spacing) terrain data from the Shuttle Radar Topography Mission (SRTM) (Figure 1a), as well as, three intermediate terrain resolution data sets produced by applying a uniform convolution window to the SRTM data with varying window sizes (Figure 1b-d). These are compared to the WRF terrain data interpolated to the high-resolution microscale grid (Figure 1e) in order to determine the impact of low-resolution (about 1 km grid spacing) terrain data on turbulence generation. The wind field is compared at several heights and distances along the dominant wind flow axis between each of the terrain cases. It is found that the development of turbulence across the domain is accelerated as terrain information increases in fidelity. Further, because this ramp event at the location of interest is largely influenced by the interaction of the short-wave trough with the terrain, as the topographic information decreases in fidelity the accuracy of the ramp event is decreased. To make generalizations and describe the benefits and shortcomings of this approach, several of the existing perturbation techniques are employed and compared to that of turbulence generation through topographic features.

17 WIND ENERGY↗