Dynamics and transport of magnetorotational instabilities in Taylor--Couette flows

泰勒-库埃特流中磁旋转不稳定性的动力学和输运

基本信息

批准号：
230979418
负责人：
Professor Dr. Marc Avila Canellas
金额：
--
依托单位：
Zentrum für angewandte Raumfahrttechnologie und Mikrogravitation (ZARM)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2013
资助国家：
德国
起止时间：
2012-12-31 至 2017-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/230979418?language=en
关键词：
Dynamics transport magnetorotational instabilities Taylor

项目摘要

Turbulent transport of gas is a necessary physical process to explain the rates at which matter accretes and solar systems form in astrophysical disks. However, angular momentum increases radially in such disks and hence gas motion is expected to be laminar according to the Rayleigh criterion for rotating fluids. The solution to this riddle is provided by the magnetorotational instability (MRI), which operates in disks provided that the gas is ionized. In the last two decades there has been a great deal of numerical studies studying the properties of the MRI. Simulations are usually performed using the shearing sheet approximation, which is a local model of an accretion disk. Recently, there has been considerable interest in obtaining the MRI in laboratory experiments. The canonical experiment for the MRI is the swirling flow of a liquid metal between two concentric and independently rotating cylinders with an imposed axial magnetic field. Linear stability studies of this problem have been carried out, and shown to be in reasonable agreement with experiment for helical magnetic fields. However, little is known of the nonlinear saturation, bifurcation scenario, transition to turbulence and transport properties of the MRI, which is crucial for accretion in disks.The main goal of this project is to provide a characterization of magnetorotational instabilities in flows between corotating cylinders in the nonlinear regime. The various flavors of the MRI, corresponding to different magnetic field configurations, will be contrasted with one another, and transport scaling will be computed and used to infer properties in the astrophysical context. The results will be extensively compared with properties of the same instability in the shearing sheet approximation, in which the imposed radially periodic boundary conditions are thought to play a key role in the nonlinear saturation and properties of the turbulent flow. The project will provide a wealth of data for benchmarking and especially for comparison with laboratory experiments that have already been performed or are either under way or planned.

气体的湍流传输是解释天体物理圆盘中物质吸积和太阳系形成速率的必要物理过程。然而，角动量在这种盘中径向增加，因此根据旋转流体的瑞利准则，气体运动预计为层流。磁旋转不稳定性（MRI）提供了这个谜题的答案，只要气体被电离，磁旋转不稳定性就会在圆盘中运行。在过去的二十年里，人们对 MRI 的特性进行了大量的数值研究。通常使用剪切片近似进行模拟，这是吸积盘的局部模型。最近，人们对在实验室实验中获得 MRI 产生了很大的兴趣。 MRI 的典型实验是液态金属在两个同心且独立旋转的圆柱体之间旋转流动，并施加轴向磁场。已经对该问题进行了线性稳定性研究，结果表明与螺旋磁场的实验结果相当一致。然而，人们对 MRI 的非线性饱和、分岔情况、湍流转变和输运特性知之甚少，而这些特性对于盘中的吸积至关重要。该项目的主要目标是提供同转圆柱体之间流动中磁转不稳定性的表征在非线性状态下。与不同磁场配置相对应的 MRI 的各种风格将相互对比，并且将计算传输缩放并用于推断天体物理背景中的属性。结果将与剪切板近似中相同不稳定性的特性进行广泛比较，其中施加的径向周期性边界条件被认为在非线性饱和和湍流特性中起着关键作用。该项目将为基准测试提供大量数据，特别是与已经进行、正在进行或计划进行的实验室实验进行比较。