Angular momentum transport in a stratified Taylor-Couette experiment with applications to accretion disks

分层泰勒-库埃特实验中的角动量传输及其在吸积盘中的应用

基本信息

批准号：
251213433
负责人：
Professor Dr.-Ing. Christoph Egbers
金额：
--
依托单位：
Leibniz-Institut für Astrophysik Potsdam (AIP)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2014
资助国家：
德国
起止时间：
2013-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/251213433?language=en
关键词：
Angular momentum transport stratified Taylor

项目摘要

Understanding the mechanisms that can result in an outward angular momentum transport is the central problem of planet formation, particularly in the theory of accretion disks. When a planet forms in a disk, angular momentum has to be carried away from the planet otherwise its rotation speed would be far too large. Only turbulence can achieve such a large angular momentum transport. For disks coupled to a magnetic field the Magneto Rotational Instability (MRI) leads to Magneto Hydrodynamic Turbulence and an associated momentum transport. However, accretion disks can be turbulent even in the absence of a magnetic field, e.g. in regions where the ionization fraction is low. In such regions, the disk cannot be unstable due to MRI and it is an important question to ask whether other instabilities can excite turbulence there. Among other candidates the Strato Rotational Instability (SRI) has attracted attention in recent years. The SRI is a purely hydrodynamic instability and much insight can be obtained from particularly designed laboratory experiments and numerical simulations in an axially-stratified Taylor-Couette (TC) setup. Here the stable axial stratification corresponds with the stratification of the disk while the disk's differential rotation can be approximated by rotating the inner and outer cylinder with different speed. We plan to investigate experimentally and numerically the instability and nonlinear saturation of temperature stratified TC flows in a finite height cylindrical gap and measure/calculate angular-momentum transport in the linear and nonlinear regime. The unstable flow transports angular momentum outwards and will therefore be relevant for astrophysical applications. We will consider different regimes and compare the experimental and numerical findings. In particular, we will measure (i) the transition curve over the full range of numerically feasible Reynolds numbers, (ii) the torque in the stable, unstable, and turbulent regime and we will consider the corresponding spatial patterns, and (iii) the transition to turbulence, the energy spectra in the transition and the turbulent regime, and we want to validate the existence of waves or wave turbulence. The study will give quantitative insight into problems of planet formation and accretion disks.

了解可能导致向外角动量传输的机制是行星形成的核心问题，尤其是在增生磁盘理论中。当行星在磁盘中形成时，必须将角动量从行星上移开，否则其旋转速度将太大。只有湍流才能实现如此大的角动量传输。对于与磁场耦合的磁盘，磁电旋转不稳定性（MRI）导致磁铁流体动力湍流和相关的动量转运。但是，即使没有磁场，也可能是湍流的，例如在电离分数低的区域中。在这样的区域，由于MRI，磁盘不能不稳定，这是一个重要的问题，要询问其他不稳定性是否可以刺激那里的湍流。在其他候选人中，Strato旋转不稳定（SRI）近年来引起了人们的关注。 SRI是一种纯粹的流体动力不稳定性，可以从特别设计的实验室实验和轴向分层的Taylor-Couette（TC）设置中获得很多洞察力。在这里，稳定的轴向分层与磁盘的分层相对应，而磁盘的差异旋转可以通过以不同的速度旋转内部和外部气缸来近似。我们计划在实验和数值上研究温度分层的TC流动在有限的高度圆柱间隙中的不稳定性和非线性饱和度，并测量/计算线性和非线性状态下的角度摩托符传输。不稳定的流动向外传递角动量，因此将与天体物理应用有关。我们将考虑不同的制度，并比较实验和数值发现。特别是，我们将测量（i）在数值可行的雷诺数中的整个范围内的过渡曲线，（ii）稳定，不稳定和湍流的扭矩，我们将考虑相应的空间模式，（iii）过渡到过渡和湍流中的能量光谱和湍流和湍流和湍流和湍流和湍流的过渡。该研究将对行星形成和增生磁盘的问题进行定量洞察力。