Computation of 3D Hydrodynamic, Hydromagnetic and Dust-Laden Flows in Protoplanetary Disks and Their Roles in Planetesimal and Star Formation

本文的研究重点是围绕年轻恒星的原行星盘中的质量和角动量输运。“湍流”或“涡粘性”被用来解决各种问题，包括从盘向外输送角动量，使质量吸积到中央原恒星上，尘埃的积累产生微行星，以及它们作为增强粘性的能力，使微行星或行星在盘中径向迁移，远离它们形成的区域。然而，用“涡动粘度”计算角动量、尘埃、微行星和行星在盘内的输运率可能是不正确的。在这里，另一个过程的可持续性，磁流体动力学湍流（这是高度耗散）和它的transferrangular动量的能力，将作为磁盘的电离功能进行研究。此外，研究人员以前的工作表明，旋涡是有效的运输角动量。他的3D模型进一步表明，谷物可以被困在这些漩涡中并集中起来。使用两个新的代码，一个混合粒子/气体代码和其他在两相流代码，其中一个阶段是气体和其他的灰尘，灰尘的积累在磁盘的中平面，在一个磁盘内形成的涡流，并在涡流区的湍流将被检查。所有这些位置都被认为是尘埃集中的区域，然后经过凝聚或不稳定产生微行星。还将研究一个提议的方案，即原行星盘充满旋涡。在这个模型中，一个小的初始扰动会产生微弱的重力内波。这些波，在旋转，剪切分层流，创建涡流。这些涡旋不是稳定的，而是振荡的，产生了新的重力波，圆盘中充满了波和涡旋。这里使用的工具也适用于其他问题，包括木星大气的循环，模拟宽体飞机产生的尾涡，以及微粒在气候污染中的作用。这项工作的成果将通过公开讲座和通俗文章向公众传播。一名研究生将在流体流动的数值模拟方面得到支持和培训。

ABSTRACTThe research to be carried out here centers on the transportation of mass and angularmomentum in protoplanetary disks surrounding young stars. "Turbulence" or "eddyviscosities" have been invoked to solve a variety of problems, including the transport ofangular momentum outward from a disk to allow mass to accrete onto a central protostar,the accumulation of dust to produce planetesimals, and their ability to act as an enhancedviscosity which allows planetesimals or planets to migrate radially in the disk away fromthe regions in which they formed. However, computing the transport of angularmomentum, dust, planetesimals, and planets within a disk using transport rates from"eddy viscosities" may well be incorrect. Here, the sustainability of another process,magnetohydrodynamic turbulence (which is highly dissipative) and its ability to transportangular momentum, will be studied as a function of the disk's ionization. In addition, theinvestigator's previous work has shown that vortices are efficient at transporting angularmomentum. His 3D modeling further indicates that grains can be trapped in these vorticesand concentrated. Using two new codes, one a hybrid particle/gas code and the other atwo-phase flow code in which one phase is the gas and the other is the dust, theaccumulation of dust in the disk's mid-plane, in the vortices that form within a disk, andin the inter-eddy regions of the turbulence will be examined. All of these locations havebeen suggested to be regions where dust concentrates and then undergoes agglomerationor instability to produce planetesimals. A proposed scenario by which protoplanetarydisks fills with vortices will also be investigated. In this model a small, initialperturbation produces weak internal gravity waves. Those waves, in a rotating, shearingstratified flow, create vortices. The vortices are not steady, but oscillate, creating newgravity waves, and the disk fills with waves and vortices.The tools employed here are applicable to other problems as well, including thecirculation of Jupiter's atmosphere, modeling wake-vortices produced by wide bodyaircraft, and the role of particulates in climate pollution. The results of this work will bedisseminated to the public through public lectures and popular articles. A graduatestudent will be supported and trained in numerical modeling of fluid flows.