The Graduate University for Advanced Studies, SOKENDAI, Toki, Gifu, 509-5292, Japan.
National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan.
Sci Rep. 2023 Mar 16;13(1):2319. doi: 10.1038/s41598-023-29168-w.
A simplified model to estimate nonlinear turbulent transport only by linear calculations is proposed, where the turbulent heat diffusivity in tokamak ion temperature gradient(ITG) driven turbulence is reproduced for a wide parameter range including near- and far-marginal ITG stability. The optimal nonlinear functional relation(NFR) between the turbulent diffusivity, the turbulence intensity [Formula: see text], and the zonal-flow intensity [Formula: see text] is determined by means of mathematical optimization methods. Then, an extended modeling for [Formula: see text] and [Formula: see text] to incorporate the turbulence suppression effects and the temperature gradient dependence is carried out. The simplified transport model is expressed as a modified nonlinear function composed of the linear growth rate and the linear zonal-flow decay time. Good accuracy and wide applicability of the model are demonstrated, where the regression error of [Formula: see text] indicates improvement by a factor of about 1/4 in comparison to that in the previous works.
提出了一种仅通过线性计算来估计非线性湍流输运的简化模型，该模型再现了托卡马克离子温度梯度（ITG）驱动湍流中的湍流传热导率，涵盖了近边界和远边界 ITG 稳定性的广泛参数范围。通过数学优化方法确定了湍流传热导率、湍流强度[公式：见文本]和带状流强度[公式：见文本]之间的最优非线性函数关系（NFR）。然后，进行了[公式：见文本]和[公式：见文本]的扩展建模，以纳入湍流抑制效应和温度梯度依赖性。简化的输运模型表示为一个修改后的非线性函数，由线性增长率和线性带状流衰减时间组成。该模型具有很好的准确性和广泛的适用性，其中[公式：见文本]的回归误差表明与之前的工作相比提高了约 1/4。
