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

气体的湍流传输是解释天体物理盘中物质吸积和太阳系形成速率的必要物理过程。然而，角动量径向增加，在这样的磁盘，因此气体运动预计是层流根据瑞利标准旋转流体。磁旋转不稳定性（MRI）提供了这个谜题的答案，它在气体被电离的情况下在圆盘中运行。在过去的二十年里，已经有大量的数值研究研究的MRI的属性。模拟通常使用剪切片近似，这是一个本地模型的吸积盘。最近，人们对在实验室实验中获得MRI产生了相当大的兴趣。MRI的典型实验是在两个同心且独立旋转的圆柱体之间的液体金属的旋流，其具有施加的轴向磁场。线性稳定性的研究，这个问题已经进行，并表明是在合理的协议与实验螺旋磁场。然而，很少有人知道的非线性饱和，分叉的情况下，过渡到湍流和运输性能的MRI，这是至关重要的吸积在disks.The主要目标是提供一个表征磁旋转不稳定性的非线性政权之间的流动共转圆柱。对应于不同磁场配置的各种MRI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下的属性。结果将被广泛地比较剪切片近似，其中施加的径向周期性边界条件被认为是发挥关键作用的非线性饱和和湍流特性的相同的不稳定性的属性。该项目将提供丰富的数据，用于制定基准，特别是与已经进行或正在进行或计划进行的实验室实验进行比较。

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.