Diagnosing collisionless energy transfer using field–particle correlations: Vlasov–Poisson plasmas

2017 ◽  
Vol 83 (1) ◽  
Author(s):  
Gregory G. Howes ◽  
Kristopher G. Klein ◽  
Tak Chu Li
Keyword(s):  
Energy Transfer ◽  
Large Scale ◽  
Physical Space ◽  
Landau Damping ◽  
One Dimension ◽  
Correlation Technique ◽  
Analysis Tool ◽  
Primary Analysis ◽  
Particle Correlation ◽  
Turbulent Fluctuations

Turbulence plays a key role in the conversion of the energy of large-scale fields and flows to plasma heat, impacting the macroscopic evolution of the heliosphere and other astrophysical plasma systems. Although we have long been able to make direct spacecraft measurements of all aspects of the electromagnetic field and plasma fluctuations in near-Earth space, our understanding of the physical mechanisms responsible for the damping of the turbulent fluctuations in heliospheric plasmas remains incomplete. Here we propose an innovative field–particle correlation technique that can be used to measure directly the secular energy transfer from fields to particles associated with collisionless damping of the turbulent fluctuations. Furthermore, this novel procedure yields information about the collisionless energy transfer as a function of particle velocity, providing vital new information that can help to identify the dominant collisionless mechanism governing the damping of the turbulent fluctuations. Kinetic plasma theory is used to devise the appropriate correlation to diagnose Landau damping, and the field–particle correlation technique is thoroughly illustrated using the simplified case of the Landau damping of Langmuir waves in a 1D-1V (one dimension in physical space and one dimension in velocity space) Vlasov–Poisson plasma. Generalizations necessary to apply the field–particle correlation technique to diagnose the collisionless damping of turbulent fluctuations in the solar wind are discussed, highlighting several caveats. This novel field–particle correlation technique is intended to be used as a primary analysis tool for measurements from current, upcoming and proposed spacecraft missions that are focused on the kinetic microphysics of weakly collisional heliospheric plasmas, including the Magnetospheric Multiscale (MMS), Solar Probe Plus, Solar Orbiter and Turbulence Heating ObserveR (THOR) missions.

scholarly journals Collisionless energy transfer in kinetic turbulence: field–particle correlations in Fourier space

2019 ◽  
Vol 85 (4) ◽  
Author(s):  
Tak Chu Li ◽  
Gregory G. Howes ◽  
Kristopher G. Klein ◽  
Yi-Hsin Liu ◽  
Jason M. TenBarge
Keyword(s):  
Solar Wind ◽  
Energy Transfer ◽  
Low Frequency ◽  
Particle Energy ◽  
Distribution Functions ◽  
Velocity Space ◽  
Correlation Technique ◽  
Direction Parallel ◽  
Particle Correlation ◽  
Particle Correlations

Turbulence is commonly observed in nearly collisionless heliospheric plasmas, including the solar wind and corona and the Earth’s magnetosphere. Understanding the collisionless mechanisms responsible for the energy transfer from the turbulent fluctuations to the particles is a frontier in kinetic turbulence research. Collisionless energy transfer from the turbulence to the particles can take place reversibly, resulting in non-thermal energy in the particle velocity distribution functions (VDFs) before eventual collisional thermalization is realized. Exploiting the information contained in the fluctuations in the VDFs is valuable. Here we apply a recently developed method based on VDFs, the field–particle correlation technique, to a $\unicode[STIX]{x1D6FD}=1$ , solar-wind-like, low-frequency Alfvénic turbulence simulation with well-resolved phase space to identify the field–particle energy transfer in velocity space. The field–particle correlations reveal that the energy transfer, mediated by the parallel electric field, results in significant structuring of the VDF in the direction parallel to the magnetic field. Fourier modes representing the length scales between the ion and electron gyroradii show that energy transfer is resonant in nature, localized in velocity space to the Landau resonances for each Fourier mode. The energy transfer closely follows the Landau resonant velocities with varying perpendicular wavenumber $k_{\bot }$ and plasma $\unicode[STIX]{x1D6FD}$ . This resonant signature, consistent with Landau damping, is observed in all diagnosed Fourier modes that cover the dissipation range of the simulation.

scholarly journals Diagnosing collisionless energy transfer using field–particle correlations: Alfvén-ion cyclotron turbulence

2020 ◽  
Vol 86 (4) ◽  
Author(s):  
Kristopher G. Klein ◽  
Gregory G. Howes ◽  
Jason M. TenBarge ◽  
Francesco Valentini
Keyword(s):  
Energy Transfer ◽  
Electric Field ◽  
Transfer Rate ◽  
Velocity Space ◽  
Turbulence Energy ◽  
Correlation Technique ◽  
Parallel Electric Field ◽  
Particle Correlation ◽  
Particle Correlations ◽  
Ion Cyclotron

We apply field–particle correlations – a technique that tracks the time-averaged velocity-space structure of the energy density transfer rate between electromagnetic fields and plasma particles – to data drawn from a hybrid Vlasov–Maxwell simulation of Alfvén-ion cyclotron turbulence. Energy transfer in this system is expected to include both Landau and cyclotron wave–particle resonances, unlike previous systems to which the field–particle correlation technique has been applied. In this simulation, the energy transfer rate mediated by the parallel electric field $E_{\Vert }$ comprises approximately 60 % of the total rate, with the remainder mediated by the perpendicular electric field $E_{\bot }$ . The parallel electric field resonantly couples to protons, with the canonical bipolar velocity-space signature of Landau damping identified at many points throughout the simulation. The energy transfer mediated by $E_{\bot }$ preferentially couples to particles with $v_{tp}\lesssim v_{\bot }\lesssim 3v_{tp}$ , where $v_{tp}$ is the proton thermal speed, in agreement with the expected formation of a cyclotron diffusion plateau. Our results demonstrate clearly that the field–particle correlation technique can distinguish distinct channels of energy transfer using single-point measurements, even at points in which multiple channels act simultaneously, and can be used to determine quantitatively the rates of particle energization in each channel.

Small-scale structure and energy transfer in homogeneous turbulence

2018 ◽  
Vol 854 ◽  
pp. 505-543 ◽  
Author(s):  
Douglas W. Carter ◽  
Filippo Coletti
Keyword(s):  
Energy Transfer ◽  
Large Scale ◽  
Probability Distributions ◽  
Physical Space ◽  
Energy Cascade ◽  
Homogeneous Turbulence ◽  
Small Scale ◽  
Mean Flow ◽  
Number Range ◽  
Wide Range

We use high-resolution velocity measurements in a jet-stirred zero-mean-flow facility to investigate the topology and energy transfer properties of homogeneous turbulence over the Reynolds number range $Re_{\unicode[STIX]{x1D706}}\approx 300$–500. The probability distributions of the enstrophy and strain-rate fields show long tails associated with the most intense events, while the weaker events behave as random variables. The high-enstrophy and high-strain structures are shaped as tube-like and sheet-like objects, respectively, the latter often wrapped around the former. Both types of structures have thickness that scales in Kolmogorov units, and display self-similar topology over a wide range of scales. The small-scale turbulence activity is found to be strongly correlated with the large-scale activity, suggesting that the phenomenon of amplitude modulation (previously observed in advection-dominated shear flows) is not limited to specific production mechanisms. Observing the significant variations in spatially averaged enstrophy, we heuristically define hyperactive and sleeping states of the flow: these also correspond to, respectively, high and low levels of large-scale velocity gradients. Moreover, the hyperactive and sleeping states contribute very differently to the inter-scale energy flux, characterized via the nonlinear transfer term in the Kármán–Howarth–Monin equation. While the energy cascades to smaller scales along the jet-axis direction, a weaker but sizable inverse transfer is observed along the transverse direction; a behaviour so far only observed in spatially developing flows. The hyperactive states are characterized by very intense energy transfers, while the sleeping states account for weaker fluxes, largely directed from small to large scales. This implies that the form of energy cascade depends on the presence (or absence) of intense turbulent structures. These results are at odds with the classic concept of the energy cascade between adjacent scales, but are compatible with the view of a cascade in physical space.

scholarly journals PRISMS-Fatigue computational framework for fatigue analysis in polycrystalline metals and alloys

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Mohammadreza Yaghoobi ◽  
Krzysztof S. Stopka ◽  
Aaditya Lakshmanan ◽  
Veera Sundararaghavan ◽  
John E. Allison ◽  
...  
Keyword(s):  
Open Source ◽  
Open Source Software ◽  
Large Scale ◽  
Metals And Alloys ◽  
Analysis Tool ◽  
Computational Framework ◽  
Crystal Plasticity Finite Element ◽  
Polycrystalline Metals ◽  
Simulation Based ◽  
Open Source Framework

AbstractThe PRISMS-Fatigue open-source framework for simulation-based analysis of microstructural influences on fatigue resistance for polycrystalline metals and alloys is presented here. The framework uses the crystal plasticity finite element method as its microstructure analysis tool and provides a highly efficient, scalable, flexible, and easy-to-use ICME community platform. The PRISMS-Fatigue framework is linked to different open-source software to instantiate microstructures, compute the material response, and assess fatigue indicator parameters. The performance of PRISMS-Fatigue is benchmarked against a similar framework implemented using ABAQUS. Results indicate that the multilevel parallelism scheme of PRISMS-Fatigue is more efficient and scalable than ABAQUS for large-scale fatigue simulations. The performance and flexibility of this framework is demonstrated with various examples that assess the driving force for fatigue crack formation of microstructures with different crystallographic textures, grain morphologies, and grain numbers, and under different multiaxial strain states, strain magnitudes, and boundary conditions.

scholarly journals Characterization of Pharmaceutical Tablets Using UV Hyperspectral Imaging as a Rapid Line to Line Analysis Tool

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4436
Author(s):  
Mohammad Al Ktash ◽  
Mona Stefanakis ◽  
Barbara Boldrini ◽  
Edwin Ostertag ◽  
Marc Brecht
Keyword(s):  
Hyperspectral Imaging ◽  
Large Scale ◽  
Solid Phase ◽  
Ultra Violet ◽  
Principal Component ◽  
Ccd Camera ◽  
Conveyor Belt ◽  
Hyperspectral Data ◽  
Analysis Tool ◽  
Sample Set

A laboratory prototype for hyperspectral imaging in ultra-violet (UV) region from 225 to 400 nm was developed and used to rapidly characterize active pharmaceutical ingredients (API) in tablets. The APIs are ibuprofen (IBU), acetylsalicylic acid (ASA) and paracetamol (PAR). Two sample sets were used for a comparison purpose. Sample set one comprises tablets of 100% API and sample set two consists of commercially available painkiller tablets. Reference measurements were performed on the pure APIs in liquid solutions (transmission) and in solid phase (reflection) using a commercial UV spectrometer. The spectroscopic part of the prototype is based on a pushbroom imager that contains a spectrograph and charge-coupled device (CCD) camera. The tablets were scanned on a conveyor belt that is positioned inside a tunnel made of polytetrafluoroethylene (PTFE) in order to increase the homogeneity of illumination at the sample position. Principal component analysis (PCA) was used to differentiate the hyperspectral data of the drug samples. The first two PCs are sufficient to completely separate all samples. The rugged design of the prototype opens new possibilities for further development of this technique towards real large-scale application.

scholarly journals Energy release and conversion by reconnection in the magnetotail

2005 ◽  
Vol 23 (10) ◽  
pp. 3365-3373 ◽  
Author(s):  
J. Birn ◽  
M. Hesse
Keyword(s):  
Energy Transfer ◽  
Energy Release ◽  
Large Scale ◽  
Magnetic Energy ◽  
Minor Role ◽  
Ohmic Dissipation ◽  
Particle Simulations ◽  
Minor Part ◽  
Reconnection Site ◽  
A Minor

Abstract. Magnetic reconnection is the crucial process in the release of magnetic energy previously stored in the magnetotail in association with substorms. However, energy transfer and dissipation in the vicinity of the reconnection site is only a minor part of the energy conversion. We discuss the energy release, transport, and conversion based on large-scale resistive MHD simulations of magnetotail dynamics and more localized full particle simulations of reconnection. We address in particular, where the energy is released, how it propagates and where and how it is converted from one form into another. We find that Joule (or ohmic) dissipation plays only a minor role in the overall energy transfer. Bulk kinetic energy, although locally significant in the outflow from the reconnection site, plays a more important role as mediator or catalyst in the transfer between magnetic and thermal energy. Generator regions with potential auroral consequences are located primarily off the equatorial plane in the boundary regions of the plasma sheet.

Experimental and Analytical Studies on Flexure Pivot Tilting Pad Gas Bearings With Dampers Applied to Radially Compliant Pads

2009 ◽  
Author(s):  
Daejong Kim ◽  
Aaron Rimpel
Keyword(s):  
Simulation Method ◽  
Analysis Tool ◽  
Primary Analysis ◽  
Successful Operation ◽  
Gas Bearings ◽  
Viscoelastic Dampers ◽  
Thermal Growth ◽  
Tilting Pad ◽  
Rotor Bearing ◽  
First Time

Hydrodynamic flexure pivot tilting pad gas bearings (FPTPGBs) can enable successful operation of oil-free microturbomachinery, and FPTPGBs with radially compliant pads (FPTPGB-Cs) permit rotor centrifugal and/or thermal growth to exceed original bearing clearances and achieve higher speeds. This work presents the experimental and analytical study of such bearings and the application of dampers behind the pad radial compliance structure. A time domain orbit simulation method was implemented as the primary analysis tool to predict rotor-bearing response to imbalance, the presence and location of critical speeds, etc., and compare with test results. Experiments demonstrate the stable hydrodynamic operation of FPTPGBs with a ∼28.6 mm, 0.8 kg rotor above 120 krpm for the first time. The rotor-bearing system was intentionally destabilized in tests by increasing bearing clearances, and viscoelastic dampers added behind the FPTPGB pads delayed the onset of subsynchronous vibrations (from 43 krpm without damper to above 50 krpm with damper). Midrange subsynchronous vibrations of the destabilized system initiated at ∼20 krpm were suppressed by ∼25 krpm due to the stabilizing effect of rotor centrifugal growth. The viscoelastic dampers had a negligible effect on suppressing these midrange subsynchronous vibrations in experiments, but this was not demonstrated in simulations, presumed to be due to much lower stiffness contribution of the damper at lower frequencies.

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