论文标题
对天体物理湍流的亚网格规模模型的A-Priori验证
A-priori Validation of Subgrid-scale Models for Astrophysical Turbulence
论文作者
论文摘要
我们对动量，能量和被动标量的湍流运输进行亚网格尺度（SGS）模型的A-Priori验证测试。为此，我们使用Lagrangian代码进行了两组高分辨率的流体动力学模拟：一个等温湍流盒，RMS马赫数为0.3、2和8，以及经典的风洞，其中冷云通过热介质逐渐由于流体不稳定而逐渐溶解。研究了两个SGS模型：在天体物理模拟中疯狂采用的涡流扩散率（ED）模型，以及由于Clark等人而引起的“梯度模型”。 （1979）。我们发现，这两个模型都可以很好地预测SGS项的大小（相关系数> 0.8）。但是，梯度模型在SGS项的方向和形状方面提供了出色的预测，而ED模型在两者的预测上都较差，这表明各向同性扩散是瞬时湍流转运的近似值较差。梯度模型的最佳拟合系数在动量传输的[0.16，0.21]范围内，而湍流的Schmidt数字和PRANDTL数字都接近统一，在[0.92，1.15]的范围内。
We perform a-priori validation tests of subgrid-scale (SGS) models for the turbulent transport of momentum, energy and passive scalars. To this end, we conduct two sets of high-resolution hydrodynamical simulations with a Lagrangian code: an isothermal turbulent box with rms Mach number of 0.3, 2 and 8, and the classical wind tunnel where a cold cloud traveling through a hot medium gradually dissolves due to fluid instabilities. Two SGS models are examined: the eddy diffusivity (ED) model wildly adopted in astrophysical simulations and the "gradient model" due to Clark et al. (1979). We find that both models predict the magnitude of the SGS terms equally well (correlation coefficient > 0.8). However, the gradient model provides excellent predictions on the orientation and shape of the SGS terms while the ED model predicts poorly on both, indicating that isotropic diffusion is a poor approximation of the instantaneous turbulent transport. The best-fit coefficient of the gradient model is in the range of [0.16, 0.21] for the momentum transport, and the turbulent Schmidt number and Prandtl number are both close to unity, in the range of [0.92, 1.15].
