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Research of the interaction among different spatio-temporal scale turbulence and transport structure

不同时空尺度湍流与输运结构相互作用研究

基本信息

批准号：
15560721
负责人：
KISHIMOTO Yasuaki
金额：
$ 1.79万
依托单位：
Graduate School of Energy Science, Kyoto University (2004-2005)Japan Atomic Energy Agency (2003)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

项目摘要

Based on the idea that various prominent structures in thermonuclear fusion plasmas like tokamak are established resulting from complex interaction among different spatio-temporal scale fluctuations, we studied fundamental principles of the interaction in turbulent transport process. The main results are as follows :1) Based on theory and simulation using gyro-fluid model, we clarified the dynamics of zonal flows and its structures produced by nonlinear interaction of micro-scale electron temperature gradient (ETG) turbulence. We investigated a "partition law" between turbulent fluctuation and zonal fluctuation and found that the partition is controlled by magnetic shear. Specifically, we found that in weak and/or reversed magnetic shear plasmas a large portion of fluctuation energy is efficiently transferred to zonal fluctuation in high pressure gradient regime and then anomalousness of turbulent transport disappears.2) We studied the effects of the micro-scale ETG-driven zonal flows … More observed in the above process (1) on macro-scale ion temperature gradient (ITG) turbulent transport and found that an intermittent behavior is exhibited in the heat diffusivity near the ITG critical gradient. This may results from complex interplay among ITG turbulence, ITG-driven zonal flow and also micro-scale ETG-driven zonal flow. The result indicates that treating key physical processes with different spatio-temporal scales in wide wave number and frequency space simultaneously is important.3) In order to clarify the relation between secondary generated large scale convective structure and structure of maternal turbulence, we developed a modulational instability analysis and found that the convective structure is significantly influenced by the structure of turbulence. Namely, zonal flows are preferentially excited from radially elongated turbulence structure, whereas streamers are produced from poloidally elongated turbulence structure. Thus, the secondary large scale structure is found to be controlled by the structure of maternal turbulence.4) In order to characterize the transport dynamics where the turbulent component and zonal component are mixed, we investigated statistical quantities such as probability distribution function (PDF), fractal dimension, wavelet spectrum, bi-coherence, etc. We found that the fractal dimension is significantly reduced in plasmas dominated by zonal flows, suggesting that the suppressed transport is sustained by rather coherent process. Less

基于托卡马克等热核聚变等离子体中各种突出结构是由不同时空尺度涨落之间的复杂相互作用产生的思想，我们研究了湍流输运过程中相互作用的基本原理。主要研究结果如下：1)基于陀螺流体模型的理论和模拟，阐明了微尺度电子温度梯度(ETG)湍流非线性相互作用产生的层流动力学及其结构。我们研究了湍流涨落和纬向涨落之间的“分配法则”，发现分配是由磁剪切控制的。具体来说，我们发现在弱和/或反向磁剪切等离子体中，很大一部分涨落能量被有效地转移到高压梯度状态下的带状涨落，然后湍流输运的异常现象消失。2）我们研究了上述过程（1）中观察到的微尺度ETG驱动的带状流对宏观尺度离子温度梯度（ITG）湍流输运的影响，发现：在 ITG 临界梯度附近的热扩散率表现出间歇性行为。这可能是由于 ITG 湍流、ITG 驱动的纬向流以及微尺度 ETG 驱动的纬向流之间复杂的相互作用造成的。结果表明，同时处理宽波数和频率空间中不同时空尺度的关键物理过程具有重要意义。3）为了阐明次生大尺度对流结构与母体湍流结构之间的关系，我们进行了调制不稳定性分析，发现对流结构受湍流结构的显着影响。即，纬向流优先由径向拉长的湍流结构激发，而流注则由极向拉长的湍流结构产生。因此，发现次级大尺度结构是受母体湍流结构控制的。4）为了表征湍流成分和纬向成分混合的输运动力学，我们研究了概率分布函数（PDF）、分形维数、小波谱、双相干性等统计量。我们发现，在纬向流主导的等离子体中，分形维数显着降低，这表明被抑制的运输是通过相当连贯的过程维持的。较少的