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Results for “parameter sensitivity”

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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

SOLEDGE3X full vessel plasma boundary simulations of ITER non-active phase plasmas

The onset of detachment in the ITER machine is analyzed in this work through the help of 2D-axisymmetric boundary plasma simulations with the SOLEDGE3X-EIRENE code, which features a numerical domain for the plasma solver extending up to the first wall. The plasma boundary is computed in scenarios from the first non-active phase of ITER, in pure H and at 20 MW. This set of simulations is used in two aspects: first, to study the plasma detachment in the divertor, and second, the plasma conditions, fluxes, and beryllium erosion at the first wall. Here, the code results are also compared to those obtained with the well-established SOLPS-ITER code, which includes a plasma numerical domain only covering the main SOL. Results show an increase in the SOL width λ q with increasing density, and a detailed analysis is carried out, for the first time, on each of the different plasma-neutral interactions in the code’s physics model in EIRENE. The gross beryllium erosion rates of first wall panels are estimated from 2D simulations, with the aim of assessing their sensitivity to two parameters: the divertor density regime, and the presence of density shoulders in the far-SOL formed by enhanced perpendicular transport at this location. The erosion contributions from neutrals and ions are considered in each case, and the charge-exchange atoms fluxes and energy distributions are provided, highlighting the two atom populations (cold and charge-exchange).

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

First measurement of symmetric cumulants of hexagonal flow harmonics in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV

Correlations between event-by-event fluctuations of anisotropic flow harmonics are measured in Pb-Pb collisions at a center-of-mass energy per nucleon pair of 5.02 TeV, as recorded by the ALICE detector at the LHC. This study presents correlations up to the hexagonal flow harmonic 𝑣 6 , which was measured for the first time. The magnitudes of these higher-order correlations are found to vary as a function of collision centrality and harmonic order. These measurements are compared to viscous hydrodynamic model calculations with EKRT initial conditions and to the iEBE-VISHNU model with T R ⁢ENTo initial conditions. The observed discrepancies between the data and the model calculations vary depending on the harmonic combinations. Due to the sensitivity of model parameters estimated with Bayesian analyses to these higher-order observables, the results presented in this work provide new and independent constraints on the initial conditions and transport properties in theoretical models used to describe the system created in heavy-ion collisions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Model-independent determination of the strong-phase difference between D 0 and D ¯ 0 → π + π − π + π − decays

Measurements of the strong-phase difference between D 0 and D ¯ 0 → π + π − π + π − are performed in bins of phase space. The study exploits a sample of quantum-correlated D D ¯ mesons collected by the BESIII experiment in e + e − collisions at a center-of-mass energy of 3.773 GeV, corresponding to an integrated luminosity of 2.93 fb − 1 . Here, D denotes a neutral charm meson in a superposition of flavor eigenstates. The reported results are valuable for measurements of the C P -violating phase γ (also denoted ϕ 3 ) in B ± → D K ± , D → π + π − π + π − decays, and the binning schemes are designed to provide good statistical sensitivity to this parameter. The expected uncertainty on γ arising from the precision of the strong-phase measurements, when applied to very large samples of B -meson decays, is around 1.5° or 2°, depending on the binning scheme. The binned strong-phase parameters are combined to give a value of F + 4 π = 0.746 ± 0.010 ± 0.004 for the C P -even fraction of D 0 → π + π − π + π − decays, which is around 30% more precise than the previous best measurement of this quantity. Published by the American Physical Society 2024

Ablikim, M.↗
DOE OSTI2026

FIREFLY: heat load and particle exhaust approximations for rapid evaluation of divertor designs

The divertor in a magnetic confinement fusion reactor is an essential component for power dissipation and particle removal. The FIREFLY package for rapid evaluation of divertor designs is presented as an extension of the FLARE code for field line reconstruction from a flux tube mesh. First, divertor loads are approximated with a simplified heat transport model. Neutralized particles are then sampled from the resulting load distribution, and the EIRENE code is used to track molecules and atoms in a plasma background while accounting for dissociation, charge exchange and ionization. Particles are removed on pumping surfaces in order to estimate the exhaust efficiency for a given divertor geometry. Optimization of the divertor geometry for more efficient particle exhaust is explored by using W7-X as an example, and the sensitivity to model parameters for the plasma background in the proxy calculations is evaluated.

mesh generation, magnetic field lines, scrape-off ↗
NASA NTRS1972

Heat pipes for spacecraft temperature control: Their usefulness and limitations

Heat pipes are used in spacecraft to equalize the temperature of structures and maintain temperature control of electronic components. Information is provided for a designer on: (1) a typical mounting technique, (2) choices available in wick geometries and fluids, (3) tests involved in flight-qualifying the design, and (4) heat pipe limitations. An evaluation of several heat pipe designs showed that the behavior of heat pipes at room temperature does not necessarily correlate with the classic equations used to predict their performance. They are sensitive to such parameters as temperature, fluid inventory, orientation, and noncondensable gases.

Ollendorf, S.↗
NASA NTRS1971

Optimal flash rate and duty cycle for flashing visual indicators.

This experiment examined the ability of observers to determine, as quickly as possible, whether a visual indicator was steadily on or flashing. Six flash rates (periods) were combined factorially with three duty cycles (on-off ratios) to define 18 ?types' of intermittent signals. Experimental sessions were divided into six runs of 100 trials, each run utilizing one of the six flash rates. On any given trial in a run, the probability of a steady signal occurring was 0.5 and the probability of a flashing signal occurring was 0.5. A different duty cycle was employed daily for each experimental session. In all, 400 trials were devoted to each of the flash rates at each duty cycle. Accuracy and latency of response were the dependent variables of interest. The results show that the observers view the light for an interval of time appropriate to the expected flash rate and duty cycle; whether they judge the light to be steady or intermittent depends upon whether the light is extinguished during the predetermined waiting period. Adoption of this temporal criterion delays responding in comparison to those tasks involving responses to light onset. The decision or response criteria held by the observers are also sensitive to the parameters of the flashing light: observers become increasingly willing to call a flashing light ?steady' as flash duration increases.

Markowitz, J.↗
NASA NTRS1972

Space Tug Aerobraking Study. Volume 2: Technical

The feasibility and practicality of employing an aerobraking trajectory for return of the reusable Space Tug from geosynchronous and other high energy missions was investigated. The aerobraking return trajectory modes from high orbits employ transfer ellipses which have low perigee altitudes wherein the earth's sensible atmosphere provides drag to reduce the Tug descent delta velocity requirements and thus decrease the required return trip propulsive energy. An aerobraked Space Tug, sized to the Space Shuttle payload capability and dimensional constraints, can accomplish 95 percent of the geosynchronous missions with a single Shuttle/Tug launch per mission. Aerodynamics, aerothermodynamics, trajectory, quidance and control, configuration concepts, materials, weights and performance parameters were identified. Sensitivities to trajectory uncertainties, atmospheric anomalies and re-entry environments were determined. New technology requirements and future studies required to further enhance the aerobraking potential were identified.

Corso, C. J.↗
NASA NTRS1973

Experimental investigation of orthotropic panel flutter at arbitrary yaw angles, and comparison with theory

Flutter characteristics for yaw angles between 15 deg and 90 deg were determined experimentally for two types of corrugation-stiffened panels: those with weak twisting stiffness and those with strong twisting stiffness. By mounting the panels on a remotely controlled turntable, good definition of the flutter boundaries was obtained by rotating the panels into and out of flutter. Flutter tests were conducted at M = 2 and M = 1.6. Before testing, vibration tests and analyses were also performed. The experimental flutter data is compared with flutter theory for orthotropic panels utilizing quasi-steady aerodynamics. Five different corrugated panels were tested consisting of one single skin panel having a length-to-width ratio of 5 on clamped supports and four different square double skin panels on discrete flexible supports. The investigation indicated that flutter speed for corrugated panels is highly dependent on yaw angle. Reasonable flutter correlation between analysis and test was obtained for moderate yaw angles, but extreme sensitivity to structural parameters made the correlation at large yaw angles uncertain.

Shyprykevich, P.↗
NASA NTRS1974

Theory of discrete vortex noise

A solution is obtained for the noise induced by vortex shedding from the trailing edge of a semiinfinite flat plate. The method of solution for the potential flow is based on a procedure whereby an inner incompressible flow is matched to an outer acoustic field. Acoustic wave fronts are calculated and compared qualitatively with schlieren photographs of similar flows. The acoustic directivity pattern is obtained, and the extreme sensitivity of this parameter to the incompressible flow near the trailing edge of the plate is investigated.

Davis, S. S.↗
NASA NTRS1974

Boundaries of ERTS and aircraft data within which useful water quality information can be obtained

Calibration procedures have been devised and applied to ERTS-1, multispectral, true color, and false color imagery. The results indicate that the ERTS and multispectral imagery are correlated with optical in situ measurements of the harbor water. Correlation is extended to true and false color imagery through in situ optical measurements of the harbor water. The best photometric accuracy is achieved with multispectral aerial imagery and the use of bulk MSS tape. The aircraft green photographic and ERTS-1 MSS-4 bands have been found most suitable for monitoring the scattered light levels under the conditions of this investigation. The application of satellite or aircraft for optical remote sensing depends upon the physical scale and frequency of sensing since both sensor systems generally have sufficient photometric sensitivity. The chemical parameters of the harbor water were found to be correlated to the optical properties for two stations investigated in detail.

Egan, W. G.↗
NASA NTRS1975

Attitude and orbit estimation using stars and landmarks

An extended Kalman filter is used to process line-of-sight measurements to stars and known landmarks providing a statistical indication of performance in estimating spacecraft attitude, orbital ephemeris, and the bias drift of a set of three strapdown gyros. The landmark measurements were assumed to have been taken from the imagery of an Earth-observing multispectral scanner. It is shown that filtering of these noisy measurements results in highly accurate estimates of the above parameters. Results are given showing the sensitivity of performance to various system parameters such as star tracker accuracy, errors in the knowledge of landmark position, and number of stars and landmarks processed.

White, R. L.↗
NASA NTRS1976

Remote sensing of atmospheric pollutant gases using an infrared heterodyne spectrometer

Remote sensing of the concentration and vertical distribution of atmospheric gases using an infrared heterodyne spectrometer (IHS) has been investigated, and a dual (C-13)(O-16)2 laser multichannel IHS has been developed. Analyses of nadir thermal-radiance measurements from an aircraft at 10-km altitude and of solar absorption measurements from the ground indicate that initial applications of the IHS to tropospheric measurements of NH3 and O3 are feasible with measurement precisions ranging from 0.5 to 2 ppb and 20 to 30 ppb, respectively. These analyses have included effects of potential retrieval-error sources and have resulted in specifications of measurement modes, optimum signature lines, required system parameters, and expected sensitivities. Preliminary instrument performance data are presented.

Seals, R. K., Jr.↗
NASA NTRS1976

Roughness induced transition criteria for space shuttle-type vehicles

Tripping effectiveness of surface roughness on a delta wing shuttle orbiter model at 20 deg angle of attack is compared to that on plane and axisymmetrical bodies with and without longitudinal pressure gradients. The experimental data presented are compared on the basis of effective roughness Reynolds number since this parameter is not sensitive to flow conditions downstream of the roughness. The discussion covers the effective roughness Reynolds number as a function of roughness position Reynolds number, effective size ratio as a function of pressure gradient and distance from vehicle nose, and effect of spanwise roughness position on roughness effectiveness. It is shown that conventional criteria for sizing roughness elements which promote transition in two-dimensional zero-pressure gradient flows are insufficient for high-pressure gradient flows and three-dimensional flows. Roughness much smaller than that given by conventional criteria can cause transition and significantly increase the heating load.

Morrisette, E. L.↗
NASA NTRS1977

Cost benefit analysis of the transfer of NASA remote sensing technology to the state of Georgia

The author has identified the following significant results. First order benefits can generally be quantified, thus allowing quantitative comparisons of candidate land cover data systems. A meaningful dollar evaluation of LANDSAT can be made by a cost comparison with equally effective data systems. Users of LANDSAT data can be usefully categorized as performing three general functions: planning, permitting, and enforcing. The value of LANDSAT data to the State of Georgia is most sensitive to the parameters: discount rate, digitization cost, and photo acquisition cost. Under a constrained budget, LANDSAT could provide digitized land cover information roughly seven times more frequently than could otherwise be obtained. Thus on one hand, while the services derived from LANDSAT data in comparison to the baseline system has a positive net present value, on the other hand if the budget were constrained, more frequent information could be provided using the LANDSAT system than otherwise be obtained.

Zimmer, R. P.↗