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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Resummation of electroweak Sudakov logarithms for real radiation

Using the known resummation of virtual corrections together with knowledge of the leading-log structure of real radiation in a parton shower, we derive analytic expressions for the resummed real radiation after they have been integrated over all of phase space. Performing a numerical analysis for both the 13 TeV LHC and a 100 TeV pp collider, we show that resummation of the real corrections is at least as important as resummation of the virtual corrections, and that this resummation has a sizable effect for partonic center of mass energies exceeding √s=O(few TeV). For partonic center of mass energies √s≳10 TeV, which can be reached at a 100 TeV collider, resummation becomes an O(1) effect and needs to be included even for rough estimates of the cross-sections.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Pure quark and gluon observables in collinear drop

We construct a class of pure quark and gluon observables by using the collinear drop grooming technique. The construction is based on linear combinations of multiple cumulative distributions of the jet mass in collinear drop, whose specific weights are fully predicted perturbatively. This yields observables which obtain their values purely from quarks (or purely from gluons) in a wide region of phase space. We demonstrate this by showing that these observables are effective in two phase space regions, one dominated by perturbative resummation and one dominated by nonperturbative effects. The nonperturbative effects are included using shape functions which only appear as a common factor in the linear combinations constructed. We test this construction using a numerical analysis with next-to-leading logarithmic resummation and various shape function models, as well as analyzing these observables with PYTHIA and VINCIA. Choices for the collinear drop parameters are optimized for experimental use.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Microstrata

Abstract Microstrata are the non-extremal analogues of superstrata: they are smooth, non-extremal (non-BPS) solitonic solutions to IIB supergravity whose deep-throat limits approximate black holes. Using perturbation theory and numerical methods, we construct families of solutions using a consistent truncation to three-dimensional supergravity. The most general families presented here involve two continuous parameters, or amplitudes, and four quantized parameters that set the angular momenta and energy levels. Our solutions are asymptotic to the vacuum of the D1-D5 system: AdS 3 ×S 3 × 𝕋 4 . Using holography, we show that the they are dual to multi-particle states in the D1-D5 CFT involving a large number of mutually non-BPS supergravitons and we determine the anomalous dimensions of these states from the binding energies in supergravity. These binding energies are uniformly negative and depend non-linearly on the amplitudes of the states. In one family of solutions, smoothness restricts some of the fields to lie on a special locus of the parameter space. Using precision holography we show that this special locus can be identified with the multi-particle states constructed via the standard OPE of the single-particle constituents. Our numerical analysis shows that microstrata are robust at large amplitudes and the solutions can be obtained to very high precision.

Physics↗
DOE OSTI2016

Closure of the operator product expansion in the non-unitary bootstrap

We use the numerical conformal bootstrap in two dimensions to search for finite, closed sub-algebras of the operator product expansion (OPE), without assuming unitarity. We find the minimal models as special cases, as well as additional lines of solutions that can be understood in the Coulomb gas formalism. All the solutions we find that contain the vacuum in the operator algebra are cases where the external operators of the bootstrap equation are degenerate operators, and we argue that this follows analytically from the expressions in arXiv:1202.4698 for the crossing matrices of Virasoro conformal blocks. Our numerical analysis is a special case of the “Gliozzi” bootstrap method, and provides a simpler setting in which to study technical challenges with the method. In the supplementary material, we provide a Mathematica notebook that automates the calculation of the crossing matrices and OPE coefficients for degenerate operators using the formulae of Dotsenko and Fateev.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Quantum Spectral Methods for Differential Equations

Recently developed quantum algorithms address computational challenges in numerical analysis by performing linear algebra in Hilbert space. Such algorithms can produce a quantum state proportional to the solution of a d-dimensional system of linear equations or linear differential equations with complexity poly(logd). While several of these algorithms approximate the solution to within ϵ with complexity poly(log(1/ϵ)), no such algorithm was previously known for differential equations with time-dependent coefficients. In this work, we develop a quantum algorithm for linear ordinary differential equations based on so-called spectral methods, an alternative to finite difference methods that approximates the solution globally. Using this approach, we give a quantum algorithm for time-dependent initial and boundary value problems with complexity poly(logd, log(1/ϵ)).

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

Geomechanical Model Calibration Using Field Measurements for a Petroleum Reserve

A finite element numerical analysis model has been constructed that consists of a mesh that effectively captures the geometries of Bayou Choctaw (BC) Strategic Petroleum Reserve (SPR) site and multimechanism deformation (M-D) salt constitutive model using the daily data of actual wellhead pressure and oil–brine interface location. The salt creep rate is not uniform in the salt dome, and the creep test data for BC salt are limited. Therefore, the model calibration is necessary to simulate the geomechanical behavior of the salt dome. The cavern volumetric closures of SPR caverns calculated from CAVEMAN are used as the field baseline measurement. The structure factor, A 2 , and transient strain limit factor, K o , in the M-D constitutive model are used for the calibration. The value of A 2 , obtained experimentally from BC salt, and the value of K o , obtained from Waste Isolation Pilot Plant salt, are used for the baseline values. To adjust the magnitude of A 2 and K0, multiplication factors A 2 F and K o F are defined, respectively. The A 2 F and K0F values of the salt dome and salt drawdown skins surrounding each SPR cavern have been determined through a number of back analyses. The cavern volumetric closures calculated from this model correspond to the predictions from CAVEMAN for six SPR caverns. Therefore, this model is able to predict behaviors of the salt dome, caverns, caprock, and interbed layers. In conclusion, the geotechnical concerns associated with the BC site from this analysis will be explained in a follow-up paper.

02 PETROLEUM↗
DOE OSTI2021

Flowback Test Analyses at the Utah Frontier Observatory for Research in Geothermal Energy (FORGE) Site

Abstract In 2017 and 2019, injection testing was carried out in three zones in a vertical well in granite at the Frontier Observatory for Research in Geothermal Energy site near Milford, Utah, USA. In several injection cycles, flowback was implemented rather than shut-in. The goal was to explore an alternative to prolonged shut-in periods for inferring closure stress, formation compressibility, and formation permeability (permeability thickness product). The flowback procedures involved a cyclic flowback/shut-in, while pressure decreased. The flowback data are presented, and analyses are shown. The inferred closure stress(es) from flowback analyses are lower than for equivalent injection cycles that were strictly shut-in. Relatively high formation compressibility obtained from the flowback analyses indicates an extensive, fractured system. This study also includes numerical simulation of the flowback events. The numerical model shows that the rebound pressure is not necessarily the lower bound of the minimum principal stress. The signature of stiffness change can be identified as the process when the depletion mainly transitions from hydraulic fracture to natural fractures from numerical analysis. Overall, flowback potentially has advantages over shut-in because of the reduced time to closure.

15 GEOTHERMAL ENERGY↗
DOE OSTI2024

On the Departure from Monin–Obukhov Surface Similarity and Transition to the Convective Mixed Layer

Large-eddy simulations are used to evaluate mean profile similarity in the convective boundary layer (CBL). Particular care is taken regarding the grid sensitivity of the profiles and the mitigation of inertial oscillations in the simulation spin-up. The nondimensional gradients Φ for wind speed and air temperature generally align with Monin–Obukhov similarity across cases but have a steeper slope than predicted within each profile. The same trend has been noted in several other recent studies. The Businger-Dyer relations are modified here with an exponential cutoff term to account for the decay in Φ to first-order approximation, yielding improved similarity from approximately 0.05z i to above 0.3z i , where z i is the CBL depth. The necessity for the exponential correction is attributed to an extended transition from surface scaling to zero gradient in the mixed layer, where the departure from Monin–Obukhov similarity may be negligible at the surface but becomes substantial well below the conventional surface layer height of 0.1 z i .

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Hierarchical Model Reduction Driven by Machine Learning for Parametric Advection-Diffusion-Reaction Problems in the Presence of Noisy Data

Abstract We propose a new approach to generate a reliable reduced model for a parametric elliptic problem, in the presence of noisy data. The reference model reduction procedure is the directional HiPOD method, which combines Hierarchical Model reduction with a standard Proper Orthogonal Decomposition, according to an offline/online paradigm. In this paper we show that directional HiPOD looses in terms of accuracy when problem data are affected by noise. This is due to the interpolation driving the online phase, since it replicates, by definition, the noise trend. To overcome this limit, we replace interpolation with Machine Learning fitting models which better discriminate relevant physical features in the data from irrelevant unstructured noise. The numerical assessment, although preliminary, confirms the potentialities of the new approach.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2023

Nonlinear dynamics, bifurcations, and multi-stability in a vibro-impact system with geometric and multi-segmented freeplay nonlinearities

Freeplay is a common type of piecewise-smooth nonlinearity in dynamical systems, and it can cause discontinuity-induced bifurcations and other behaviors that may bring about undesirable and potentially damaging responses. Prior research has focused on piecewise-smooth systems with two or three distinct regions, but less attention is devoted to systems with more regions (i.e., multi-segmented systems). In this work, numerical analysis is performed on a dynamical system with multi-segmented freeplay, in which there are four stiffness transitions and five distinct regions in the phase space. Here, the effects of the multi-segmented parameters are studied through bifurcation diagram evolution along with induced multi-stable behavior and different bifurcations. These phenomena are interrogated through various tools, such as harmonic balance, basins of attraction, phase planes, and Poincaré section analysis. Results show that among the three multi-segmented parameters, the asymmetry has the strongest effect on the response of the system.

42 ENGINEERING↗
DOE OSTI2019

Design and engineering of dispersion and loss in photonic crystal fiber 1 × 4 power splitter (PCFPS) based on hole size alteration and optofluidic infiltration

We have presented a technique based on optofluidic infiltration and air-holes diameter variation together to design a 1 × 4 photonic crystal fiber power splitter (PCFPS) which have very low dispersion (D): (0 ≤ D ≤ 2.5 (ps/nm/km) and very low loss (L): 0 ≤ L ≤ 0.025(dB/cm) in a wide range of wavelengths (1100–1700 nm). This approach allows us to control the dispersion of the fundamental mode in a PCF beam splitter by choosing appropriate refractive indices for liquids and suitable diameters for air-holes in PCF power splitter. In fact, the techniques, used in this paper are complementary of each other and give us more excellent results which are better than other reported results in researchers’ works so far. In this work, a new design of 1 × 4 photonic crystal fiber power splitter is proposed by using beam propagation method. An optical Gaussian signal at a wavelength of third communication window range (1550 nm) is inserted into the central core and equally is divided into four core (25% of the total input power interred to each core). In addition, the physical behavior of coupling characteristics is obtained by using coupled mode analysis. Numerical simulations show that input optical signal can be equally divided in photonic crystal fiber structure with low dispersion and low loss. The total size of proposed PCFPS is 30 µm × 30 µm × 1.2 mm, too.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Explicit dispersion relations for warm fluid waves in a uniform plasma (invited)

Classical dispersion relations for waves in a fluid plasma are expressed as implicit functions of wave frequency and wave- number. The implicit dispersion relation must in general be solved numerically. This work introduces an astute method for obtaining an explicit dispersion relation for waves in a fluid plasma. The explicit expression has an advantage of providing eigenmodes without numerical computations and giving a dispersion relation more detailed than the implicit expression. As in the case of cold waves, the wavenumber for an arbitrary frequency can be directly obtained from the explicit formula. The explicit formula also enables an accurate evaluation of finite-temperature effects on a dispersion relation even near the cyclotron resonance, where a numerical analysis of the implicit relation is impractical. As a result, the analytic formula can be used to investigate temperature effects on electromagnetic waves.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Combined experimental and numerical evaluation of a prototype nano-PCM enhanced wallboard

In the United States, forty-eight (48) percent of the residential end-use energy consumption is spent on space heating and air conditioning. Reducing envelope-generated heating and cooling loads through application of phase change material (PCM)-enhanced building envelopes can facilitate maximizing the energy efficiency of buildings. Combined experimental testing and numerical modeling of PCM-enhanced envelope components are two important aspects of the evaluation of their energy benefits. An innovative phase change material (nano-PCM) was developed with PCM encapsulated with expanded graphite (interconnected) nanosheets, which is highly conductive for enhanced thermal storage and energy distribution, and is shape-stable for convenient incorporation into lightweight building components. A wall with cellulose cavity insulation and prototype PCM-enhanced interior wallboards was built and tested in a natural exposure test (NET) facility in a hot-humid climate location. The test wall contained PCM wallboards and regular gypsum wallboard, for a side-by-side annual comparison study. Further, numerical modeling of the walls containing the nano-PCM wallboard was performed to determine its actual impact on wall-generated heating and cooling loads. The model was first validated using experimental data, and then used for annual simulations using Typical Meteorological Year (TMY3) weather data. This article presents the measured performance and numerical analysis evaluating the energy-saving potential of the nano-PCM-enhanced wallboard.

finite element analysis↗
DOE OSTI2024

Resonant Raman in armchair graphene nanoribbons from first-principles

Resonant Raman spectra of armchair graphene nanoribbons (AGNRs) are computed using Density Functional Theory (DFT) and third-order perturbation theory. Results are benchmarked against available experimental data and compared to previously used theoretical approaches based on the Placzek approximation. Comparable agreement with experiments is found for both previously and presently used methods. In addition, a numerical analysis is carried out to provide a justification for the resonant modeling method based on the use of the frequency-dependent dielectric tensor in the Placzek approximation. Finally, this work also provides additional predictions and references for wide AGNRs that might be investigated with Raman scattering experiments in the future.

42 ENGINEERING↗
DOE OSTI2019

Experimental study of ethanol oxidation behind reflected shock waves: Ignition delay time and H 2 O laser-absorption measurements

The oxidation of ethanol was investigated in shock tubes by measuring ignition delay times and water time history profiles. A laser absorption technique was used in the latter case. Ignition delay times were investigated for three equivalence ratios, 0.5, 1.0, and 2.0, and for pressures ranging from 1.3 to 53 atm. The fuel concentration and the type of diluent used were also varied. The ignition delay times were in very good agreement with results from the literature for the very few overlapping conditions, and most of the experimental conditions have never been studied before. A high level of accuracy was observed for the predictions of the ignition delay times from detailed kinetics mechanisms. Inhomogeneous ignition events were observed in some specific conditions, validating the notions of thermal diffusivity and flame thickness developed in the literature for the reasons behind such inhomogeneous ignition. The water time-history profiles showed the formation of water in two stages. These profiles were also modeled using well-known detailed kinetic mechanisms from the literature. Severe discrepancies were often observed for laser-absorption measurements, and this was the case with most of the models. A numerical analysis (sensitivity and rate-of-production) was conducted using the two best-performing literature mechanisms (namely, AramcoMech3.0 and CRECK).

42 ENGINEERING↗
DOE OSTI2020

Plasma decay in hydrocarbons and hydrocarbon- and H 2 O-containing mixtures excited by high-voltage nanosecond discharge at elevated gas temperatures

Plasma decay after a high-voltage nanosecond discharge was experimentally and numerically studied in pure hydrocarbons (C 2 H 6 and C 3 H 8 ), and H 2 O:N 2 and C 3 H 8 :O 2 mixtures for pressures in the range 2–4 Torr and gas temperatures from 300 to 600 K. In a stoichiometric C 3 H 8 :O 2 mixture, plasma decay was also studied in a repetitively pulsed discharge for varing numbers of discharge pulses (varying degrees of fuel oxidation). The rate of plasma decay was determined from the temporal evolution of electron density measured using the microwave interferometer. It was observed that gas heating to 600 K leads to a decrease in the rate of plasma decay in all cases. The effect of heating on plasma decay was most profound in the H 2 O:N 2 mixture (after a single discharge pulse) and in the C 3 H 8 :O 2 mixture for high degrees of fuel oxidation. A kinetic scheme was developed to numerically simulate the plasma decay in hydrocarbons and combustible mixtures. Numerical analysis showed that, under the conditions studied, plasma decay was controlled by dissociative electron recombination with simple molecular and cluster ions. Gas heating led to a decrease in the rate of the electron-ion recombination and the rate of conversion of molecular ions to cluster ions. As a result, the gas temperature increase caused a decrease in the fraction of cluster ions for which the recombination coefficients are an order of magnitude higher than the recombination coefficients for molecular ions. The influence of gas heating on the decrease of the amount of cluster ions was more important when the ion composition was dominated by hydrated H 3 O + (H 2 O) k ions. The rates of the formation of these ions are extremely sensitive to any variations in gas temperature. A result, in agreement with our observations, gas heating led to an anomalous decrease in the rates of plasma decay in the H 2 O:N 2 mixture, as well as in the C 3 H 8 :O 2 mixture when H 2 O molecules were produced due to fuel oxidation.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2022

Evaluating cascaded and tunable phase change materials for enhanced thermal energy storage utilization and effectiveness in building envelopes

The incorporation of phase change materials (PCMs) in envelope is considered an effective thermal energy storage (TES) method for energy savings and load flexibility in buildings. However, an important limitation of PCMs is their fixed and narrow transition temperature range. Because the interior temperature setpoints are typically different in summer versus winter, and the exterior temperature varies substantially above and below the setpoints during the year, PCMs with a fixed transition temperature are utilized only during part of the year. In this paper, we provide an extensive numerical analysis of the performance of a lightweight building envelope containing three different types of PCMs: traditional single-layer PCM with a fixed transition temperature, novel cascaded two-layer PCM with different transition temperatures, and a "futuristic" tunable PCM whose transition temperature can be varied in-situ using external excitation. We compare their performances by evaluating the relationship between the PCM utilization and parameters such as latent heat, transition temperature range, PCM thickness, and PCM location. While traditional PCMs are mostly active during one season, properly designed cascaded and tunable PCMs can be active much longer, thereby allowing load shift and energy savings in both heating and cooling seasons. Under the operating conditions considered in this study, tunable PCMs performed best, providing the highest utilization (about 2 times the traditional PCMs) and enhanced effectiveness (up to 99% peak load reduction in cooling season and 34% peak load reduction in heating season) with the same amount of material as the traditional PCMs; however, cascaded PCMs can be a good alternative while tunable PCMs are unavailable.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2018

Near- and far-field earthquake damage study of the Konitsa stone arch bridge

This paper reports on the sensitivity of earthquake response and damage of long span masonry stone bridges to near field (impulsive type) and far field earthquakes. Towards that objective, the Konitsa Bridge is used as a case study. The particular bridge was selected for offering certain unique features such as long span, built right on an active fault, survived a recent pair of near-filed type earthquakes with minimal damage and finally, construction material mechanical properties and strength could be deduced from a recently collapsed similar bridge in the area. The multifaceted study integrated in-situ measurements of dynamic characteristics, laboratory tests on representative stone and mortar materials and a series of finite-element analyses based on non-linear modelling using a combination of discontinuous and continuous representations to capture the behavior of bridge structural component interface and interaction as well as mortar-stone interaction and failure. In addition to the ground motion records of the recent seismic activity at the Konitsa Bridge location, four additional earthquake records representing near-field and far-field families were utilized to assess the stone bridge sensitivity. The study revealed that far-field earthquakes are far more destructive than near-field counterparts, a finding in full agreement with studies on near field earthquake effects on nuclear structures. In conclusion, the applicability of earthquake damage indicators such as CAV, Arias intensity and energy rate, typically used for conventional and nuclear structures, was evaluated based on the numerical analysis results.

43 PARTICLE ACCELERATORS↗