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

作为非均匀等离子体湍流输运模型，本文研究了交换湍流。这种不稳定性在磁约束等离子体中是普遍存在的，并且与瑞利-泰勒不稳定性和贝纳德对流相似。可以参考流体动力学中关于这些不稳定性的知识。描述交换湍流的磁流体动力学模型包括瑞利数Ra和普朗特数Pr两个无量纲特征数，这些无量纲数也用于贝纳德对流的分类。为了计算由交换湍流引起的输运，采用了无量纲数努塞尔数Nu。在本研究中，通常假设普朗特数Pr=1。所得结果总结如下：1。当Ra小于或接近bbb10 ^4时，交换湍流的饱和水平变得非平稳，呈现锯齿状振荡。2.当Ra <等于或接近bbb10 ^5时，随着总波动能量锯齿状振荡的增强，由交换模式驱动的剪切流分量超过了涡分量。3.当Ra小于或接近bbb10 ^5时，湍流输运对应的努塞尔数呈间歇性增加。随着Ra的增加，爆发时Nu变大，爆发周期变长。然而，Nu的时间平均值不依赖于Ra。非线性交换模的行为似乎与在托卡马克或磁体的h模中观察到的elm（边缘局域模式）一致

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