Energy dynamics in a simulation of LAPD turbulence

Friedman, B.; Carter, Troy; Umansky, M.; Schaffner, David; Dudson, B.

doi:10.1063/1.4759010

Cited by 26 publications

(58 citation statements)

References 37 publications

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“…These results are similar to those found in [25] in that the energy dynamics (in this case dissipation) is localized to small longitudinal mode numbers. It should be noted that the nonconservative rate of change of our total energy is negative, as the only contribution is from the ohmic dissipation, D j .…”

Section: Energy Dynamicssupporting

confidence: 80%

“…An analysis of the energy dynamics within the system was performed similar to that found in reference [25]. In this work, the system is spectrally-decomposed in the azimuthal and axial directions, and the energy of each mode is analyzed to determine the energy transfer channels and dissipation.…”

Section: Energy Dynamicsmentioning

confidence: 99%

“…The individual terms in equation 7 indicate the (a) internal energy, (b) parallel kinetic energy, and (c) perpendicular kinetic energy of the system in Fourier space. The evolution of each Fourier mode can be described as [25]:…”

Section: Energy Dynamicsmentioning

confidence: 99%

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X-point modelling in linear configurations using BOUT++

Shanahan

Dudson

2014

J. Phys.: Conf. Ser.

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Abstract. Magnetic X-point configurations in tokamak geometries are critical in determining edge and scrape off layer (SOL) dynamics, and hence particle and heat flux onto plasma facing components. Alternative configurations have been proposed which aim to reduce fluxes to material surfaces, but their performance depends on cross-field transport in the region of the null point which is currently poorly understood. There is therefore a need for theoretical and experimental studies of turbulence in X-point magnetic configurations. In conventional 3D turbulence simulations of tokamaks, a field-aligned coordinate system is used, which introduces numerical instabilities at the null point due to zero volume elements. As a result, X-point dynamics are often interpolated based on nearby flux surfaces, which could exclude relevant physics. Here we simulate X-point configurations in linear geometries using a non-field-aligned coordinate system, and present results of 3D drift-wave turbulence and flow simulations in Xpoint configurations using an isothermal model which evolves density, vorticity, parallel velocity and parallel current density. Simulations have been performed to explore the feasibility of experimentally studying X-point configurations in linear plasma devices which indicate that even a modest coil set carrying 300A should produce a measurable effect on the driftwave turbulence and plasma profiles near the null region. The energy dynamics of the system are also explored and indicate that an X-point causes ohmic dissipation in higher mode number turbulence.

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Section: Energy Dynamicssupporting

confidence: 80%

Section: Energy Dynamicsmentioning

confidence: 99%

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X-point modelling in linear configurations using BOUT++

Shanahan

Dudson

2014

J. Phys.: Conf. Ser.

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“…This work will build on prior work simulating LAPD turbulence using the BOUTþþ code. [32][33][34] Plasmas 20, 055907 (2013) …”

Section: Discussionmentioning

confidence: 99%

Turbulence and transport suppression scaling with flow shear on the Large Plasma Device

et al. 2013

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Continuous control over azimuthal flow and shear in the edge of the Large Plasma Device (LAPD) [W. Gekelman et al., Rev. Sci. Instr. 62, 2875(1991] has been achieved using a biasable limiter. This flow control has allowed a careful study of the effect of flow shear on pressure-gradient-driven turbulence and particle transport in LAPD. The combination of externally controllable shear in a turbulent plasma along with the detailed spatial diagnostic capabilities on LAPD makes the experiment a useful testbed for validation of shear suppression models. Motivated by these models, power-law fits are made to the density and radial velocity fluctuation amplitudes, particle flux, density-potential crossphase, and radial correlation length. The data show a break in the trend of these quantities when the shearing rate (c s ¼ @V h =@r) is comparable to the turbulent decorrelation rate (1=s ac ). No one model captures the trends in the all turbulent quantities for all values of the shearing rate, but some models successfully match the trend in either the weak (c s s ac < 1) or strong (c s s ac > 1) shear limits. V C 2013 AIP Publishing LLC. [http://dx

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“…Reynolds numbers are predicated on the separation of energy injection and dissipation scales. However, drift-wave turbulence may not have a clear separation of scales as energy can potentially be injected or dissipated at different scales [40], and thus a Reynolds number may have less meaning in this case. The complexity-entropy analysis performed here, on the other hand, does not rely on any specific physical model and thus can be used to compare disparate systems.…”

Section: Ch Comparison Of Ssx Wind and Lapd Datamentioning

confidence: 99%

Permutation entropy and statistical complexity analysis of turbulence in laboratory plasmas and the solar wind

et al. 2015

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. 2015. Permutation entropy and statistical complexity analysis of turbulence in laboratory plasmas and the solar wind. Phys. Rev. E 91, 023101.PHYSICAL REVIEW E 91, 023101 (2015) Permutation entropy and statistical complexity analysis of turbulence in laboratory plasmas and the solar wind The Bandt-Pompe permutation entropy and the Jensen-Shannon statistical complexity are used to analyze fluctuating time series of three different turbulent plasmas: the magnetohydrodynamic (MHD) turbulence in the plasma wind tunnel of the Swarthmore Spheromak Experiment (SSX), drift-wave turbulence of ion saturation current fluctuations in the edge of the Large Plasma Device (LAPD), and fully developed turbulent magnetic fluctuations of the solar wind taken from the Wind spacecraft. The entropy and complexity values are presented as coordinates on the CH plane for comparison among the different plasma environments and other fluctuation models. The solar wind is found to have the highest permutation entropy and lowest statistical complexity of the three data sets analyzed. Both laboratory data sets have larger values of statistical complexity, suggesting that these systems have fewer degrees of freedom in their fluctuations, with SSX magnetic fluctuations having slightly less complexity than the LAPD edge I sat . The CH plane coordinates are compared to the shape and distribution of a spectral decomposition of the wave forms. These results suggest that fully developed turbulence (solar wind) occupies the lower-right region of the CH plane, and that other plasma systems considered to be turbulent have less permutation entropy and more statistical complexity. This paper presents use of this statistical analysis tool on solar wind plasma, as well as on an MHD turbulent experimental plasma.

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Energy dynamics in a simulation of LAPD turbulence

Cited by 26 publications

References 37 publications

X-point modelling in linear configurations using BOUT++

X-point modelling in linear configurations using BOUT++

Turbulence and transport suppression scaling with flow shear on the Large Plasma Device

Permutation entropy and statistical complexity analysis of turbulence in laboratory plasmas and the solar wind

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