Applications of large eddy simulation methods to gyrokinetic turbulence

Navarro, A. Bañón; Teaca, Bogdan; Jenko, F.; Hammett, G. W.; Happel, T.

doi:10.1063/1.4868235

Cited by 25 publications

(41 citation statements)

References 35 publications

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“…The equation coincides with one obtained by Mahdizadeh [16]. For the case of k θ ρ s ≈ k ⊥ ρ s = 0.3, as is suggested for TEM and ITG turbulence [19], a further dependence of α on the parallel correlation length (figure 3) is obtained. If l > 10 m, the declination is expected to be < 1 • .…”

Section: Limitation Of the Methods And Declination Of Turbulent Structsupporting

confidence: 65%

Magnetic field pitch angle and perpendicular velocity measurements from multi-point time-delay estimation of poloidal correlation reflectometry

Prisiazhniuk

Krämer–Flecken

Happel

et al. 2017

Plasma Phys. Control. Fusion

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Abstract. In fusion machines turbulent eddies are expected to be aligned with the direction of the magnetic field lines and to propagate in the perpendicular direction. Time delay measurements of density fluctuations can be used for the calculation of magnetic field pitch angle α and perpendicular velocity v ⊥ profiles. The method is applied to poloidal correlation reflectometry installed at ASDEX Upgrade and TEXTOR, which measure density fluctuations from poloidally and toroidally separated antennas. Validation of the method is achieved by comparison of the perpendicular velocity (composed of the ExB drift and the phase velocity of turbulence v ⊥ = v E×B +v ph ), with Doppler reflectometry measurements, and with neoclassic fluid calculations. An important condition for the application of the method is the presence of turbulence with sufficiently long decorrelation time. It is shown that at the shear layer the decorrelation time is reduced, limiting the application of the method. The magnetic field pitch angle measured by this method shows the expected dependence on the magnetic field, plasma current and radial position. The profile of the pitch angle reproduces the expected shape and values. However, a comparison with the equilibrium reconstruction code cliste suggests an additional inclination of turbulent eddies at the pedestal position (2-3• ). This additional angle decreases towards core and at the edge.

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Section: Limitation Of the Methods And Declination Of Turbulent Structsupporting

confidence: 65%

Magnetic field pitch angle and perpendicular velocity measurements from multi-point time-delay estimation of poloidal correlation reflectometry

Prisiazhniuk

Krämer–Flecken

Happel

et al. 2017

Plasma Phys. Control. Fusion

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“…This means that experimentally, the observations are at turbulence scales which are connected to the drive scale via an energy cascade. To be able to assess the question whether changes in the measured turbulence levels are due to changes in the drive or in the spectral energy transfer properties [85][86][87], detailed measurements of wavenumber spectra are necessary, which are not available for the discharges presented here.…”

Section: Discussionmentioning

confidence: 99%

“…V A), which corresponds in these experiments to k ⊥ = 2 -4 cm −1 , dropping to larger k ⊥ . Since the turbulence level changes observed at k ⊥ = 4 -8 cm and k ⊥ = 13 -18 cm −1 ), this could point to a change in the properties of the energy cascade with collisionality and turbulence drive, as has been observed both theoretically and numerically [85][86][87]. To make a clear statement on this point, detailed measurements of wavenumber spectra are necessary, which are not available for the discharges discussed here.…”

Section: Turbulence Measurementsmentioning

confidence: 99%

Core turbulence behavior moving from ion-temperature-gradient regime towards trapped-electron-mode regime in the ASDEX Upgrade tokamak and comparison with gyrokinetic simulation

et al. 2015

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Additional electron cyclotron resonance heating (ECRH) is used in an ion-temperature-gradient instability (ITG) dominated regime to increase R/L Te in order to approach the trapped-electron-mode instability (TEM) regime. The radial ECRH deposition location determines to a large degree the effect on R/L Te . Accompanying scale-selective turbulence measurements at perpendicular wavenumbers between k ⊥ = 4 -18 cm −1 (k ⊥ ρ s = 0.7 -4.2) show a pronounced increase of large-scale density fluctuations close to the ECRH radial deposition location at mid-radius, along with a reduction in phase velocity of large-scale density fluctuations. Measurements are compared with results from linear and non-linear flux-matched gyrokinetic (GK) simulations with the gyrokinetic code gene. Linear GK simulations show a reduction of phase velocity, indicating a pronounced change in the character of the dominant instability. Comparing measurement and non-linear GK simulation, as a central result, agreement is obtained in the shape of radial turbulence level profiles. However, the turbulence intensity is increasing with additional heating in the experiment, while gyrokinetic simulations show a decrease.

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“…4 and 5 the most unstable mode for ω n = 6, ω T e = 12, varying τ . Based on previous gyrokinetic mul- (15,20,30) for (H,D,T), we assume that the ETG contribution to the transport is negligible. In order to resolve TEM or ITG turbulence we restrict to k y ρ s ≤ 3.2.…”

Section: Linear Tem Simulationsmentioning

confidence: 99%

“…14,15 This numerical technique dynamically adjusts the spatial perpendicular hyperdiffusions of the simulation. In this way we are able to reduce the number of nodes in the perpendicular directions (N x and N y ) and to speed up GENE simulations a factor of 10-20 in some cases.…”

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confidence: 99%

Microturbulence study of the isotope effect

et al. 2015

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The influence of the ion mass on the dynamics of magnetized plasmas is an important challenge in fusion research. The discrepancies between the improvement of the magnetic confinement with the ion mass in tokamak experiments and diffusive turbulent transport predictions have remained unexplained for several decades. We refer to this phenomenon as the isotope effect. In this paper we study this effect with gyrokinetic theory using the GENE code. We find several sets of plasma parameters that correspond to low wavenumber turbulence for which the isotope effect is present, although the intensity is smaller than the experimental observations. We also relate these results to the zonal flow intensity of the system, which is characterized by the average shear flow rate.

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Applications of large eddy simulation methods to gyrokinetic turbulence

Cited by 25 publications

References 35 publications

Magnetic field pitch angle and perpendicular velocity measurements from multi-point time-delay estimation of poloidal correlation reflectometry

Magnetic field pitch angle and perpendicular velocity measurements from multi-point time-delay estimation of poloidal correlation reflectometry

Core turbulence behavior moving from ion-temperature-gradient regime towards trapped-electron-mode regime in the ASDEX Upgrade tokamak and comparison with gyrokinetic simulation

Microturbulence study of the isotope effect

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