On hydrodynamic shear turbulence in Keplerian disks: Via transient growth to bypass transition
On hydrodynamic shear turbulence in Keplerian disks: Via transient growth to bypass transition
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关于开普勒圆盘中的流体动力剪切湍流：通过瞬态增长绕过转变
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
J. Lominadze
中科院分区：
文献类型：
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作者：
G. Chagelishvili;J. Zahn;A. Tevzadze;J. Lominadze
本文研究非磁化开普勒圆盘中的流体动力剪切湍流问题。最近出现了几篇关于这个问题的论文，关于可能的线性不稳定性，这可能是由于存在稳定的分层，或由圆柱旋转的偏差引起的。在这里，我们希望提请注意另一种途径的流体动力学湍流，这似乎是鲜为人知的天体物理学界，但在过去的十年中，流体动力学家进行了深入的讨论。在这种所谓的湍流发生的旁路概念中，扰动经历瞬态增长，并且如果它们最初具有有限的振幅，则它们可能达到足够大的振幅，以允许通过非线性相互作用的正反馈。这种瞬态增长本质上是线性的，因此它原则上不同于众所周知的非线性不稳定性。我们描述的类型的扰动，根据这个过程是最有可能导致湍流，即非轴对称涡模式扰动的二维限制。我们表明，明显抑制作用的科里奥利力的动态，这种涡扰动是由于压力扰动，大大减少，与目前的意见。我们强调开普勒磁盘和笛卡尔流的湍流过程的相似性，并得出结论，普遍怀疑的天体物理界的流体动力剪切湍流的发生在这样的磁盘是没有根据的。
This paper deals with the problem of hydrodynamic shear turbulence in non-magnetized Keplerian disks. Several papers have appeared recently on the subject, on possible linear instabilities which may be due to the presence of a stable stratification, or caused by deviations from cylindrical rotation. Here we wish to draw attention to another route to hydrodynamic turbulence, which seems to be little known by the astrophysical community, but which has been intensively discussed among fluid dynamicists during the past decade. In this so-called bypass concept for the onset of turbulence, perturbations undergo transient growth and if they have initially a finite amplitude they may reach an amplitude that is suciently large to allow positive feedback through nonlinear interactions. This transient growth is linear in nature, and thus it diers in principle from the well-known nonlinear instability. We describe the type of perturbations that according to this process are the most likely to lead to turbulence, namely non-axisymmetric vortex mode perturbations in the two dimensional limit. We show that the apparently inhibiting action of the Coriolis force on the dynamics of such vortical perturbations is substantially diminished due to the pressure perturbations, contrary to current opinion. We stress the similarity of the turbulent processes in Keplerian disks and in Cartesian flows and conclude that the prevalent skepticism of the astrophysical community about the occurrence of hydrodynamic shear turbulence in such disks is not founded.