Ion-scale turbulence in MAST: anomalous transport, subcritical transitions, and comparison to BES measurements
Ion-scale turbulence in MAST: anomalous transport, subcritical transitions, and comparison to BES measurements
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MAST 中的离子尺度湍流：异常输运、亚临界转变以及与 BES 测量的比较
DOI：
10.1088/1361-6587/aa8484
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发表时间：
2017
影响因子：
2.2
通讯作者：
W. Dorland
中科院分区：
文献类型：
--
作者：
F. V. Wyk;E. Highcock;A. Field;C. Roach;A. Schekochihin;F. I. Parra;W. Dorland
我们调查的影响，改变离子温度梯度（ITG）和环形平衡尺度剪切流的离子尺度的湍流在MAST的外核通过本地gyrokinetic模拟。我们表明，非线性模拟再现实验离子热通量和ITG和流动剪切的实验测量值位于接近湍流阈值。我们证明了该系统是亚临界存在的流动剪切，即，该系统在形式上对小扰动是稳定的，但在给定足够大的初始扰动时，该系统过渡到湍流状态。我们建议，过渡到亚临界湍流发生通过一个中间状态占主导地位的低数量的相干长寿命的结构，接近阈值，这增加了系统的数量从阈值到更强的湍流制度，直到他们填补了域和一个更传统的湍流出现。我们表明，湍流的属性是有效的函数的距离阈值，量化的离子热通量。我们使用MAST BES诊断我们的模拟和实验测量之间的相关长度，时间和幅度进行定量比较。我们发现合理的协议的相关性，最显着的相关时间，其中显着的差异被发现在以前的数值研究MAST湍流。
We investigate the effect of varying the ion temperature gradient (ITG) and toroidal equilibrium scale sheared flow on ion-scale turbulence in the outer core of MAST by means of local gyrokinetic simulations. We show that nonlinear simulations reproduce the experimental ion heat flux and that the experimentally measured values of the ITG and the flow shear lie close to the turbulence threshold. We demonstrate that the system is subcritical in the presence of flow shear, i.e., the system is formally stable to small perturbations, but transitions to a turbulent state given a large enough initial perturbation. We propose that the transition to subcritical turbulence occurs via an intermediate state dominated by low number of coherent long-lived structures, close to threshold, which increase in number as the system is taken away from the threshold into the more strongly turbulent regime, until they fill the domain and a more conventional turbulence emerges. We show that the properties of turbulence are effectively functions of the distance to threshold, as quantified by the ion heat flux. We make quantitative comparisons of correlation lengths, times, and amplitudes between our simulations and experimental measurements using the MAST BES diagnostic. We find reasonable agreement of the correlation properties, most notably of the correlation time, for which significant discrepancies were found in previous numerical studies of MAST turbulence.
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影响因子：
2.2
作者：
I. Abel;Michael Barnes;S. Cowley;W. Dorland;A. Schekochihin
通讯作者：
I. Abel;Michael Barnes;S. Cowley;W. Dorland;A. Schekochihin
MAST 中离子温度梯度对磁构型、旋转剪切和湍流热通量的局部依赖性
DOI：
10.48550/arxiv.1211.2883
发表时间：
2012
期刊：
arXiv e-prints
影响因子：
--
作者：
Ghim
通讯作者：
Ghim
影响因子：
2.2
作者：
Colyer, G. J.;Schekochihin, A. A.;Dorland, W.
通讯作者：
Dorland, W.
影响因子：
8.6
作者：
Barnes, M.;Parra, F. I.;Schekochihin, A. A.
通讯作者：
Schekochihin, A. A.