Fast generation of Gaussian random fields for direct numerical simulations of stochastic transport

Palade, D. I.; Vlad, M.

doi:10.1007/s11222-021-10035-5

Cited by 10 publications

(28 citation statements)

References 45 publications

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“…We have shown [32] that the representation (12) provides fast convergence of the Eulerian statistics of the generated fields, as well as of the Lagrangian statistics of trajectories. In particular, it was proven that a convergence level with a few percents error can be achieved with N c ∼ 10 d and M ∼ 10 4 , where d = 4 for time dependent potentials and d = 3 for τ d → ∞.…”

Section: Dns Numerical Methods and Codementioning

confidence: 96%

“…The model is analysed using direct numerical simulations (DNS) [32] and the decorrelation trajectory method (DTM) [33].…”

Section: Theoretical Methodsmentioning

confidence: 99%

“…The numerical methods used in the DNS code are described and analyzed in [32]. A series of fast numerical generators of Gaussian random fields with given EC are proposed.…”

Section: Dns Numerical Methods and Codementioning

confidence: 99%

“…We use two theoretical methods for determining the pinch velocity and the transport coefficients, the direct numerical simulations (DNS) [32] and the decorrelation trajectory method (DTM) [33]. A three-dimensional DNS code for ion trajectories and for the calculation of the statistical Lagragian quantities was developed.…”

Section: Introductionmentioning

confidence: 99%

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Effects of the parallel acceleration on heavy impurity transport in turbulent tokamak plasmas

Vlad,

Palade,

Spineanu

2020

Preprint

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A process specific to the dynamics of the heavy impurities in turbulent tokamak plasmas is found and analysed. We show that the parallel stochastic acceleration is strongly coupled to the perpendicular transport and generates a radial pinch velocity. The interaction is produced with the hidden drifts, a quasi-coherent component of the motion that consists of a pair of average radial velocities in opposite directions. The parallel acceleration breaks this symmetry and yields a radial average velocity that can be in the inward or outward direction. The transport of the tungsten ions in three-dimensional turbulence is analysed in the frame of a test particle model using numerical simulations. The results show that the acceleration induced pinch can be important for W impurity transport in present days tokamaks and in ITER.

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Section: Dns Numerical Methods and Codementioning

confidence: 96%

“…The model is analysed using direct numerical simulations (DNS) [32] and the decorrelation trajectory method (DTM) [33].…”

Section: Theoretical Methodsmentioning

confidence: 99%

“…The numerical methods used in the DNS code are described and analyzed in [32]. A series of fast numerical generators of Gaussian random fields with given EC are proposed.…”

Section: Dns Numerical Methods and Codementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effects of the parallel acceleration on heavy impurity transport in turbulent tokamak plasmas

Vlad,

Palade,

Spineanu

2020

Preprint

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“…From a Lagrangian perspective, one can show that, under the assumption of scale-separation [4], the transport coefficients are related to statistical averages V(t) = d t x(t) , 2 D(t) = d t ( x 2 (t) − x(t) 2 ) over ensembles of trajectories {x(t)}. The latter are driven by the corresponding ensemble of stochastic velocity fields via ẋ(t) = v(x(t), t), known as a V-Langevin equation [12,13].…”

Section: Introductionmentioning

confidence: 99%

Scaling laws of two-dimensional incompressible turbulent transport

Palade¹,

Pomârjanschi²,

Ghită³

2023

Preprint

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The diffusive transport in two-dimensional incompressible turbulent fields is investigated with the aid of high-quality direct numerical simulations. Three classes of turbulence spectra that are able to capture both short and long-range time-space correlations and oscillating features are employed. We report novel scaling laws that depart from the γ = 7/10 paradigm of percolative exponents and are dependent on the features of turbulence. A simple relation between diffusion in the percolative and frozen regimes is found. The importance of discerning between differential and integral characteristic scales is emphasized.

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Effects of intermittency via non-Gaussianity on turbulent transport in magnetized plasmas

Palade

Pomârjanschi²

2022

J. Plasma Phys.

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We analyse how the turbulent transport of $\boldsymbol {E}\times \boldsymbol {B}$ type in magnetically confined plasmas is affected by the intermittent features of turbulence. The latter are modelled via the non-Gaussian distribution $P(\phi )$ of the turbulent electric potential $\phi$ . Our analysis is performed at an analytical level and confirmed numerically using two statistical approaches. We have found that the diffusion is inhibited linearly by intermittency, mainly via the kurtosis of the distribution $P(\phi )$ . The associated susceptibility for this linear process is shown to be dependent on the poloidal velocity $V_p$ and on the correlation time $\tau _c$ (or the Kubo number $K_\star$ , the ratio between $\tau _c$ and the specific time of flight $\tau _{{\rm fl}}$ ) with a maximum at $\tau _c\approx \tau _{{\rm fl}}$ ( $K_\star \approx 1$ ). Intermittency does not affect the scaling of diffusion with the Kubo number.

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Fast generation of Gaussian random fields for direct numerical simulations of stochastic transport

Cited by 10 publications

References 45 publications

Effects of the parallel acceleration on heavy impurity transport in turbulent tokamak plasmas

Effects of the parallel acceleration on heavy impurity transport in turbulent tokamak plasmas

Scaling laws of two-dimensional incompressible turbulent transport

Effects of intermittency via non-Gaussianity on turbulent transport in magnetized plasmas

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