Dust size distributions in coagulation/fragmentation equilibrium: numerical solutions and analytical fits
Dust size distributions in coagulation/fragmentation equilibrium: numerical solutions and analytical fits
复制标题
凝结/破碎平衡中的粉尘尺寸分布：数值解和分析拟合
DOI：
10.1051/0004-6361/201015228
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发表时间：
2010
影响因子：
6.5
通讯作者：
C. Dullemond
中科院分区：
文献类型：
--
作者：
T. Birnstiel;C. Ormel;C. Dullemond
上下文星周盘中的颗粒被认为是通过相互碰撞和随后的表面力粘附而生长的。许多涉及星周盘的研究领域，如辐射传输计算、盘化学、磁流体动力学模拟等，其结果在很大程度上依赖于未知的颗粒尺寸分布。目标。由于晶粒生长和破碎的详细计算都是数值上的挑战和计算昂贵的，我们的目标是找到简单的配方和分析解决方案的晶粒尺寸分布在拱星盘的情况下，晶粒生长是有限的破碎和径向漂移可以忽略不计。方法.我们推广了以前的自相似稳态晶粒分布的分析工作。进行数值模拟，以确定在何种条件下的晶粒尺寸分布可以理解的幂律分布的组合。一个物理动机拟合公式的晶粒尺寸分布推导出使用我们的分析预测和数值模拟。结果我们发现解析结果和数值解的Smoluchowski方程的简单形状的核函数之间的协议。更复杂和现实的情况下的结果可以拟合本文提出的物理动机的“黑匣子”配方。研究结果表明，粉尘分布的形状主要受气体表面密度（而不是粉尘与气体的比值）、湍流强度和温度的控制，并不服从MRN型分布。
Context. Grains in circumstellar disks are believed to grow by mutual collisions and subsequent sticking due to surface forces. Results of many fields of research involving circumstellar disks, such as radiative transfer calculations, disk chemistry, magneto-hydrodynamic simulations largely depend on the unknown grain size distribution. Aims. As detailed calculations of grain growth and fragmentation are both numerically challenging and computationally expensive, we aim to find simple recipes and analytical solutions for the grain size distribution in circumstellar disks for a scenario in which grain growth is limited by fragmentation and radial drift can be neglected. Methods. We generalize previous analytical work on self-similar steady-state grain distributions. Numerical simulations are carried out to identify under which conditions the grain size distributions can be understood in terms of a combination of power-law distributions. A physically motivated fitting formula for grain size distributions is derived using our analytical predictions and numerical simulations. Results. We find good agreement between analytical results and numerical solutions of the Smoluchowski equation for simple shapes of the kernel function. The results for more complicated and realistic cases can be fitted with a physically motivated "black box" recipe presented in this paper. Our results show that the shape of the dust distribution is mostly dominated by the gas surface density (not the dust-to-gas ratio), the turbulence strength and the temperature and does not obey an MRN type distribution.