Study of Similarity Low with Non-dimensional Numbers for Turbulent Transport

作为非均匀等离子体中湍流输运的模型，研究了交换湍流。这种不稳定性在磁约束等离子体中具有普遍性，与瑞利-泰勒不稳定性和贝纳德对流有相似之处。可以参考流体动力学中针对这些不稳定性获得的知识。磁流体动力学模型描述的交换湍流包括两个无量纲的特征数，瑞利数，Ra和普朗特数，Pr。这些无量纲数也用于分类的Benard对流。为了评估由于交换湍流引起的传输，采用无量纲数Nusselt数Nu。在这项研究中，普朗特数通常假设Pr=1。得到的结果如下：1.当Ra = <greater than or similar>10^4时，立交湍流的饱和度变得非定常，并呈现锯齿状振荡。2.当Ra为10^5时<greater than or similar>，剪切流分量超过了交换模驱动的涡旋分量，总涨落能的锯齿状振荡增强。3.对于Ra <greater than or similar>10^5，对应于湍流输运的努塞尔数间歇性地增加。随着Ra的增加，爆发处的Nu变大，爆发周期变长。然而，Nu的时间平均值不依赖于Ra。4.这种非线性交换模的行为与托卡马克或超导托卡马克H模中观察到的边缘局域模（ELM）是一致的

As a model for turbulent transport in inhomogeneous plasmas the interchange turbulence was studied. This instability is universal for magnetically confined plasma, and has similarity to Rayleigh-Taylor instability and Benard convection. It is possible to refer knowledge obtained for these instabilities within the fluid dynamics. The magnetohydrodynamic model for describing the interchange turbulence includes two non-dimensional characteristic numbers, Rayleigh number, Ra, and Prandtl number, Pr. These non-dimensional numbers are also used for classifying the Benard convection. For evaluating The transport due to the interchange turbulence, the non-dimensional number, Nusselt number, Nu, was employed. In this study the Prandtl number is usually assumed Pr=1. The obtained results are summarized in the following.1.For Ra <greater than or similar> 10^4, the saturation level of interchange turbulence becomes non-stationary and show a sawtooth-like oscillation. 2.For Ra <greater than or similar> 10^5, the shear flow componet exceeds the vortex componet driven by the interchange mode with the enhancement of the sawtooth-like oscillation of total fluctuation energy. 3.For Ra <greater than or similar> 10^5, the Nusselt number corresponding to the turbulent transport increases intermittently. With the increase of Ra, Nu at the burst becomes large and the period of burst becomes long. However, the time average of Nu does not depend on Ra. 4.The behavior of the nonlinear interchange mode seems consistent with the ELMs (Edge Localized Modes) observed in the H-mode of tokamak or ste