Dust settling in local simulations of turbulent protoplanetary disks
Dust settling in local simulations of turbulent protoplanetary disks
复制标题
湍流原行星盘局部模拟中的尘埃沉降
DOI：
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发表时间：
2006
期刊：
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通讯作者：
J. Papaloizou
中科院分区：
文献类型：
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作者：
S. Fromang;S. Fromang;J. Papaloizou
目标。本文研究了MHD湍流对原行星盘中尘埃粒子动力学的影响。我们改变了颗粒的大小，并将尘埃的演变与湍流速度波动联系起来。方法：研究方法。我们使用两种基于有限差分技术的欧拉MHD程序进行了数值模拟：Zeus-3D和Nirvana。这些是包含垂直分层的局部剪切盒模拟。分别对具有中面死区的理想和非理想MHD进行了模拟。代码进行了扩展，将不同型号的粉尘作为额外的流体成分纳入其中。使用不同方法获得的结果之间获得了很好的一致性。结果。模拟表明，一层非常小的尘埃颗粒在整个圆盘的垂直范围内扩散开来。结果表明，用速度关联简单表示扩散系数的扩散方程所得到的简单描述与结果精确匹配。在5.2AU的标准太阳星云模型中，尘埃的沉降对于大小为1到10厘米的粒子开始变得明显，对于这种粒子，气体开始解耦。然而，对于10厘米大小的颗粒，即使在存在显著尺寸的中面死区的情况下，盘内的湍流运动也阻止了向非常薄的中面层的完全沉降。结论。这些结果表明，当存在MHD湍流时，会影响原行星盘中的尘埃动力学。我们发现，使用包含垂直沉降的平流扩散方程可以准确地模拟尘埃的演变和沉降。当几个局部轨道的时间已知时，扩散系数的值可以从湍流速度场中计算出来。
Aims. In this paper, we study the effect of MHD turbulence on the dynamics of dust particles in protoplanetary disks. We vary the size of the particles and relate the dust evolution to the turbulent velocity fluctuations. Methods. We performed numerical simulations using two Eulerian MHD codes, both based on finite difference techniques: ZEUS-3D and NIRVANA. These were local shearing box simulations incorporating vertical stratification. Both ideal and non ideal MHD simulations with midplane dead zones were carried out. The codes were extended to incorporate different models for the dust as an additional fluid component. Good agreement between results obtained using the different approaches was obtained. Results. The simulations show that a thin layer of very small dust particles is diffusively spread over the full vertical extent of the disk. We show that a simple description obtained using the diffusion equation with a diffusion coefficient simply expressed in terms of the velocity correlations accurately matches the results. Dust settling starts to become apparent for particle sizes of the order of 1 to 10 centimeters for which the gas begins to decouple in a standard solar nebula model at 5.2 AU. However, for particles which are 10 centimeters in size, complete settling toward a very thin midplane layer is prevented by turbulent motions within the disk, even in the presence of a midplane dead zone of significant size. Conclusions. These results indicate that, when present, MHD turbulence affects dust dynamics in protoplanetary disks. We find that the evolution and settling of the dust can be accurately modelled using an advection diffusion equation that incorporates vertical settling. The value of the diffusion coefficient can be calculated from the turbulent velocity field when that is known for a time of several local orbits.