The stratified Keplerian turbulence

  • Zhu, Xiaojue (Max Planck Institute)
  • Bhadra, Abhiroop (Max Planck Institute)

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Studies have revealed that Taylor-Couette flow within the Keplerian regime remains nonlinearly stable, even at high shear Reynolds numbers of up to $10^6$. Both numerical simulations and experimental observations have failed to identify any turbulence that is not attributable to interaction with axial boundaries (end plates). Consequently, there is growing evidence that the purely radial shear, may not be the sole driver of turbulence in accretion discs. The most widely accepted explanation now is the magnetorotational instability (MRI), which posits that a conducting fluid in differential rotation subjected to a magnetic field can be destabilized. However, this mechanism cannot operate in some cold and poorly ionized discs. In such cases, thermal effects, in the form of stratification in both the vertical and radial directions, may also play a key role in driving turbulence. Here, through extensive direct numerical simulations of quasi-Keplerian flow with radial stratification, we investigate the generation of turbulence and delineate the various flow regimes concerning the scaling relations of heat and angular momentum as a function of Reynolds number and Richardson number. These findings offer fresh insights into the physical constraints of angular momentum and heat transport in Keplerian turbulence.