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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS2015

Development of a SMA-Based, Slat-Gap Filler for Airframe Noise Reduction

Noise produced by unsteady flow around aircraft structures, termed airframe noise, is an important source of aircraft noise during the approach and landing phases of flight. Conventional leading-edge-slat devices for high lift on typical transport aircraft are a prominent source of airframe noise. Many concepts for slat noise reduction have been investigated. Slat-cove fillers have emerged as an attractive solution, but they maintain the gap flow, leaving some noise production mechanisms unabated, and thus represent a nonoptimal solution. Drooped-leading-edge (DLE) concepts have been proposed as "optimal" because the gap flow is eliminated. The deployed leading edge device is not distinct and separate from the main wing in DLE concepts and the high-lift performance suffers at high angles of attack (alpha) as a consequence. Elusive high-alpha performance and excessive weight penalty have stymied DLE development. The fact that high-lift performance of DLE systems is only affected at high alpha suggests another concept that simultaneously achieves the high-lift of the baseline airfoil and the noise reduction of DLE concepts. The concept involves utilizing a conventional leading-edge slat device and a deformable structure that is deployed from the leading edge of the main wing and closes the gap between the slat and main wing, termed a slat-gap filler (SGF). The deployable structure consists of a portion of the skin of the main wing and it is driven in conjunction with the slat during deployment and retraction. Benchtop models have been developed to assess the feasibility and to study important parameters. Computational models have assisted in the bench-top model design and provided valuable insight in the parameter space as well as the feasibility.

Turner, Travis L.↗
DOE OSTI2022

Turbulent Transport Studies at ASDEX Upgrade Enabled by Correlation Electron Cyclotron Emission and nT-phase Diagnostic. Final report

Work performed on project titled, "Turbulent Transport Studies at ASDEX Upgrade Enabled by Correlation Electron Cyclotron Emission and nT-phase Diagnostic". We conducted an integrated project of experiment and model validation at ASDEX Upgrade (AUG) to expand knowledge of the underlying physics of high-performance, ELM-free regimes suitable for long pulse operation. Both the I-mode and QH-mode high-confinement regimes have potential as operating scenarios in a future reactor. Additional fluctuation measurements provided critical constraints on transport models, and elucidate the transport mechanisms associated with benevolent quasi-coherent modes in the edge and pedestal region of QH-mode and I-mode. This research expanded knowledge of turbulent-transport in tokamaks in support of ITER and other burning plasma experiments.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Multi-Edge Graph Convolutional Networks for Power Systems

The exponential electrification of transportation has contributed to highly intermittent load variations in the distribution grid. This uncertainty has raised challenges for distribution system operation and control. Accurate nodal voltage estimation is highly essential for the safe and reliable operation of the grid. Graph convolutional networks have been used in machine-learning-based models for power grid applications like voltage estimation for their ability to capture the network topology of the grid. This paper presents a novel multi-edge graph convolutional layer that considers resistance and reactance as edge attributes. This layer is created by modifying the message-passing function within the graph convolutional network. The novel layer is then used to create a multi-edge graph convolutional network-based surrogate model for estimating voltage in the distribution network with highly uncertain electric vehicle loads. Results indicate improved performance of the multi-edge graph convolutional network model when compared to a standard graph convolutional network model.

Ravi, Abhijith↗
DOE OSTI2023

Defect physics in 2D monolayer I-VII semiconductor AgI

As a brand new two-dimensional (2D) material with promising electronic properties, monolayer I-VII silver iodide (AgI) has the potential for future 2D electronic devices. To advance the development of such devices, the exploration of n-type and p-type conductivities of AgI is indispensable. With first-principles calculations, we systematically investigate the properties of intrinsic defects and extrinsic dopants in monolayer AgI, including atomic structural pictures, formation energies, and ionization energies to offer carriers. Considering the divergence in energies of charged defects in 2D materials when the traditional jellium scheme is used, we adopt an extrapolation approach to overcome the problem. The Ag vacancy (VAg) and Be substitution on Ag site (BeAg) are found to be the most promising p-type and n-type doping candidates, respectively. They could provide bound carriers for transport through the defect-bound band edge states, although the ionization energies are still larger than thermal energy at room temperature. Furthermore, negative-U behaviors are demonstrated in I vacancy (VI), Zn substitution on Ag site (ZnAg), and Cd substitution on Ag site (CdAg). The present work, for the first time, offers a detailed study of the defect physics in 2D I-VII monolayer semiconductor, laying the foundation for subsequent physics and device explorations based on these brand new 2D materials.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Light Transfers Through a Koch Shape Cloud

Abstract Modeling radiative transfer in a 3D cloudy atmosphere is critical to climate projections. A recently developed fast 3D radiation parameterization scheme gains some success in quantifying horizontal radiative transfer through cloud sides using cloud area fraction. Based on 3D Monte Carlo simulations of radiative transfer through an idealized single‐layer cloud with Koch‐shaped fractal geometry edges, here we show that radiative energy transport through cloud sides correlates more significantly with cloud area fraction than with cloud perimeter length. The results exemplify the importance of accounting for the horizontal radiative energy exchanges between cloud‐free and cloudy regions with cloud area fraction. Results from additional sensitivity simulations show that increased cloud vertical extent often enhances cloud‐side sunlight leak more significantly than cloud‐side sunlight interception. At low sun elevations, cloud‐side sunlight interception is enhanced more than cloud‐side sunlight leak does with the increase of cloud mass.

58 GEOSCIENCES↗
DOE OSTI2021

Alpha particle channeling in ITER

Alpha particle channeling, the attempt to extract energy from high-energy fusion alpha particles using a combination of high- and low-frequency waves introduced in the plasma with antennae, is studied using a guiding center code. We examine the effect of the combination of cooling caused by a cyclotron mode, particle diffusion due to Alfvén modes introduced for ash removal, the inclusion of microturbulent diffusion, and the slowing down of the alpha particles on electrons. Induced cooling is achieved with a cyclotron resonance, producing additional losses of particles above 3.5 MeV in an amount about equal to the prompt loss. The removal of the low-energy cooled particles by additional modes or by microturbulent diffusion is the hardest challenge for alpha channeling. The cooled alpha particles remain deep in the plasma center, so for this removal, the method used must be capable of providing transport from the plasma center to the edge without also causing losses of high-energy particles.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Density limits as disruption forecasters for spherical tokamaks

Fusion power output from spherical tokamaks would benefit from increased confined plasma density, but there exists a limit on the density before confinement is lost and the plasma current is disrupted. This density limit has long been characterized by a simple, global Greenwald limit proportional to the plasma current and inversely proportional to the cross sectional area of the plasma. It is shown that in the database of discharges from the National Spherical Tokamak Experiment (NSTX) and Mega Ampere Spherical Tokamak (MAST) spherical tokamaks, the likelihood of disruption does increase above the Greenwald limit, and especially in the plasma current rampdown phase. The physics of the density limit has been recently theoretically explored through local criteria. Several of these are tested using the disruption event characterization and forecasting (DECAF TM ) code for their potential effectiveness as disruption warning signals. For a limited set of NSTX discharges, a local island power balance criteria was found to be less reliable, presently, than the Greenwald limit. For this work, an empirical critical edge line density and a boundary turbulent transport limit were both tested for MAST-U, which has an electron density profile measurement with high spatial resolution in the outer part of the plasma. Both were found to have similar dependencies on key plasma parameters. In a limited set of MAST-U discharges that appear to disrupt due to rising density at values under the Greenwald limit, crossing of the boundary turbulent transport limit occurred close to the time of disruption. Finally, these limits were evaluated for their potential use in real-time, and it was found that with the necessary real-time inputs and with refinement through further testing, these limits could be implemented in a real-time disruption forecasting system.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Topological edge conduction induced by strong anisotropic exchange interactions

Here, we predict that an interplay between isotropic and anisotropic exchange interactions in a honeycomb lattice structure can lead to topological edge conduction when the anisotropic interaction is at least twice the strength of the isotropic interaction. For materials like Na 2 ⁢IrO 3 , such a strong anisotropic exchange interaction simultaneously induces a zigzag type of antiferromagnetic order that breaks the time-reversal symmetry of the topological edge conductor. We show that the electronic transport in such topological conductors will exhibit a quantized Hall conductance without any external magnetic field when the Fermi energy lies within a particular energy range.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Simultaneous velocity and density measurements of fully developed Rayleigh-Taylor mixing

Here, the dynamics of molecular mixing and the energy transfer process in the Rayleigh-Taylor instability (RTI) are studied through the collection of simultaneous density-velocity measurements. These experiments provide simultaneous density-velocity field measurements, in contrast to previous point measurements. Statistically stationary experiments are performed in a “convective-type” gas tunnel facility, with density contrast achieved through the injection of helium into the bottom stream. Three experiments at Atwood number ≈ 0.1 are captured at three outer scale Reynolds numbers Re = 520, 2260, and 4050. Particle image velocimetry and laser induced fluorescence are employed simultaneously. Statistics of the density and velocity show self-similar collapse of RTI profiles at large Reynolds number Re >2000. Flat velocity profiles indicate homogeneous turbulence characteristics in the core of the mixing region. Significant anisotropy develops in the flow, with horizontal velocity fluctuations being only 60% of the vertical velocity fluctuations. The turbulent mass flux is found to be asymmetric about the centerline, with increased peak towards the spike. Measurements of the molecular mixing show that mixing is maximized at the core of the flow and increases with increased Reynolds number. The transport equation of density-specific-volume correlation b shows that it is mostly produced in the core of the mixing region, and that the spatial evolution of its profile is the result of transport by bulk motion of the bubble and spike. Energy transfer from gravitational potential energy to turbulent kinetic energy and viscous dissipation is observed to occur in the experiment with a ratio of dissipated energy to potential energy released of 38%. The analysis of the turbulent kinetic energy transport equation budget reveals that production is the primary mechanism towards the growth of turbulent kinetic energy in the core of the flow, and is asymmetrically slightly skewed towards the spike. However, it is through the transport that the strong advection at the edges of the mixing region is maintained.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1975

Experimental study of the effect on span loading on aircraft wakes

Measurements were made in the NASA-Ames 40- by 80-foot wind tunnel of the rolling moment induced on a following model in the wake 13.6 spans behind a subsonic transport model for a variety of trailing edge flap settings of the generator. It was found that the rolling moment on the following model was reduced substantially, compared to the conventional landing configuration, by reshaping the span loading on the generating model to approximate a span loading, found in earlier studies, which resulted in reduced wake velocities. This was accomplished by retracting the outboard trailing edge flaps. It was concluded, based on flow visualization conducted in the wind tunnel as well as in a water tow facility, that this flap arrangement redistributes the vorticity shed by the wing along the span to form three vortex pairs that interact to disperse the wake.

Corsiglia, V. R.↗
NASA NTRS1975

Experimental study of the effect of span loading on aircraft wakes

Measurements were made in the NASA-Ames 40- by 80-Foot Wind Tunnel of the rolling moment induced on a following model in the wake 13.6 spans behind a subsonic transport model for a variety of trailing edge flap settings of the generator. It was found that the rolling moment on the following model was reduced substantially, compared to the conventional landing configuration, by reshaping the span loading on the generating model to approximate a span loading, found in earlier studies, which resulted in reduced wake velocities. This was accomplished by retracting the outboard trailing edge flaps. It was concluded, based on flow visualization conducted in the wind tunnel as well as in a water tow facility, that this flap arrangement redistributes the vorticity shed by the wing along the span to form three vortex pairs that interact to disperse the wake.

Corsiglia, V. R.↗
NASA NTRS1988

Validation of a pair of computer codes for estimation and optimization of subsonic aerodynamic performance of simple hinged-flap systems for thin swept wings

Extensive correlations of computer code results with experimental data are employed to illustrate the use of linearized theory attached flow methods for the estimation and optimization of the aerodynamic performance of simple hinged flap systems. Use of attached flow methods is based on the premise that high levels of aerodynamic efficiency require a flow that is as nearly attached as circumstances permit. A variety of swept wing configurations are considered ranging from fighters to supersonic transports, all with leading- and trailing-edge flaps for enhancement of subsonic aerodynamic efficiency. The results indicate that linearized theory attached flow computer code methods provide a rational basis for the estimation and optimization of flap system aerodynamic performance at subsonic speeds. The analysis also indicates that vortex flap design is not an opposing approach but is closely related to attached flow design concepts. The successful vortex flap design actually suppresses the formation of detached vortices to produce a small vortex which is restricted almost entirely to the leading edge flap itself.

Carlson, Harry W.↗
NASA NTRS1987

Simulated airline service experience with laminar-flow control leading-edge systems

The first JetStar leading edge flight test was made November 30, 1983. The JetStar was flown for more than 3 years. The titanium leading edge test articles today remain in virtually the same condition as they were in on that first flight. No degradation of laminar flow performance has occurred as a result of service. The JetStar simulated airline service flights have demonstrated that effective, practical leading edge systems are available for future commercial transports. Specific conclusions based on the results of the simulated airline service test program are summarized.

Maddalon, Dal V.↗
NASA NTRS1999

Low Speed Analysis of Mission Adaptive Flaps on a High Speed Civil Transport Configuration

Thin-layer Navier-Stokes analyses were done on a high speed civil transport configuration with mission adaptive leading-edge flaps. The flow conditions simulated were Mach = 0.22 and Reynolds number of 4.27 million for angles-of-attack ranging from 0 to 18 degrees. Two turbulence closure models were used. Analyses were done exclusively with the Baldwin-Lomax turbulence model at low angle-of-attack conditions. At high angles-of-attack where considerable flow separation and vortices occurred the Spalart-Allmaras turbulence model was also considered. The effects of flow transition were studied. Predicted aerodynamic forces, moment, and pressure are compared to experimental data obtained in the 14- by 22-Foot Subsonic Tunnel at NASA Langley. The forces and moments correlated well with experimental data in terms of trends. Drag and pitching moment were consistently underpredicted. Predicted surface pressures compared well with experiment at low angles-of-attack. Above 10 angle-of-attack the pressure comparisons were not as favorable. The two turbulent models affected the pressures on the flap considerably and neither produced correct results at the high angles-of-attack.

Lessard, Victor R.↗
NASA NTRSDate not supplied

Icing Physics Studies Using the 3D SIDRM Test Article: Ice Crystal Icing Analysis

In-flight icing is an important safety issue and is a factor that affects aircraft design and performance. Newer regulations are driving a need for improvements in airframe and engine icing simulation capability. Experimental data is required for the development of icing physics models and simulation validation. This paper presents the analysis of the ice crystal icing data subset from tests conducted in 2022 at the NASA Icing Research Tunnel that studied both supercooled liquid and ice-crystal icing. The test article that was utilized replicated 3D geometrical features of an inter-compressor duct and strut region of a turbofan engine. The surfaces of the Simulated Inter-compressor Duct Research Model (SIDRM) can be heated to simulate the warm surfaces of the turbofan inter-compressor duct. The test article is instrumented with pressure taps, heaters, heat flux gauges, and thermocouples, while a 3D laser scanner, cameras, and a weighing scale to measure ice mass were utilized to characterize the icing behavior. The aim of these tests was to generate ice accretions on the SIDRM test article under well-characterized icing conditions. To that end, ice crystal cloud characterization tests were conducted that provided cloud property values at the test section. The ice crystal accretion tests investigated how different test condition parameters impacted ice accretion size, location, and characteristics (such as physical attributes). A key finding was that a sufficiently high surface heat flux at the leading edge can provide a continuous supply of liquid melt to critical accretion zones downstream, resulting in elevated ice mass accretions. Another key finding was that warmer heater settings in critical accretion zones can suppress ice accretion. These findings are consistent with icing behavior observed in full-scale engine icing tests conducted previously at the NASA Glenn Research Center. Test runs investigating the contribution of liquid melt generated at the leading edge found that the melt can be transported downstream to critical accretion regions in two forms, via runback and splash. The form of melt supplied downstream affected accretion behavior and features. Sharkteeth-shaped ice accretions were generated at certain test conditions, a physical attribute that has been observed in full-scale engine icing tests. The ice accretion data will be used to develop and validate 3D computational engine icing tools, such as GlennICE, that predictively assesses the onset and growth of ice. One of the goals of the sponsoring NASA project is to develop simulation models and tools that can assist in the design and certification of engines for flight in icing conditions in a cost‑effective way.

ice crystal icing↗
NASA NTRSDate not supplied

Icing Physics Studies Using the 3D SIDRM Test Article: Ice Crystal Icing Analysis

In-flight icing is an important safety issue and is a factor that affects aircraft design and performance. Newer regulations are driving a need for improvements in airframe and engine icing simulation capability. Experimental data is required for the development of icing physics models and simulation validation. This paper presents the analysis of the ice crystal icing data subset from tests conducted in 2022 at the NASA Icing Research Tunnel that studied both supercooled liquid and ice-crystal icing. The test article that was utilized replicated 3D geometrical features of an inter-compressor duct and strut region of a turbofan engine. The surfaces of the Simulated Inter-compressor Duct Research Model (SIDRM) can be heated to simulate the warm surfaces of the turbofan inter-compressor duct. The test article is instrumented with pressure taps, heaters, heat flux gauges, and thermocouples, while a 3D laser scanner, cameras, and a weighing scale to measure ice mass were utilized to characterize the icing behavior. The aim of these tests was to generate ice accretions on the SIDRM test article under well-characterized icing conditions. To that end, ice crystal cloud characterization tests were conducted that provided cloud property values at the test section. The ice crystal accretion tests investigated how different test condition parameters impacted ice accretion size, location, and characteristics (such as physical attributes). A key finding was that a sufficiently high surface heat flux at the leading edge can provide a continuous supply of liquid melt to critical accretion zones downstream, resulting in elevated ice mass accretions. Another key finding was that warmer heater settings in critical accretion zones can suppress ice accretion. These findings are consistent with icing behavior observed in full-scale engine icing tests conducted previously at the NASA Glenn Research Center. Test runs investigating the contribution of liquid melt generated at the leading edge found that the melt can be transported downstream to critical accretion regions in two forms, via runback and splash. The form of melt supplied downstream affected accretion behavior and features. Sharkteeth-shaped ice accretions were generated at certain test conditions, a physical attribute that has been observed in full-scale engine icing tests. The ice accretion data will be used to develop and validate 3D computational engine icing tools, such as GlennICE, that predictively assesses the onset and growth of ice. One of the goals of the sponsoring NASA project is to develop simulation models and tools that can assist in the design and certification of engines for flight in icing conditions in a cost‑effective way.

ice crystal icing↗
DOE OSTI2024

Self‐consistent transport simulation of boron dust particle injection in the peripheral plasma in Large Helical Device

Abstract The trajectories and the ablation positions of boron dust particles dropped from an impurity powder dropper in the peripheral plasma in the Large Helical Device (LHD) were calculated using a three‐dimensional edge plasma simulation code (EMC3‐EIRENE) and a dust transport simulation code (DUSTT). The simulation shows that the trajectory of the boron dust particles is deflected at the upper divertor leg due to the effect of the hydrogen plasma flow, and the ablation positions of the dust particles in an ergodic layer change toward the outboard side of the torus for higher plasma densities. The effect of the boron ion flow in the divertor leg on the deflection is investigated by coupling the two codes self‐consistently. The simulation predicts that the boron ions in the divertor leg, which are produced by sputtering on the divertor plates, which do not affect the change in the ablation positions. It also shows that the ablation positions move toward the inboard side and approach the Last Closed Flux Surface (LCFS) in case of increased boron dust drop rates, which is caused by the lowered plasma flow in the upper divertor leg due to the lowered electron temperature by radiation cooling by the dropped dust particles.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗