A pure hydrodynamic instability in shear flows and its application to astrophysical accretion disks

TL;DR

This paper demonstrates that stochastic noise can induce pure hydrodynamic linear instability in shear flows, providing a novel explanation for turbulence observed in astrophysical accretion disks and laboratory experiments.

Contribution

It introduces the role of stochastic noise in destabilizing Rayleigh stable shear flows, offering the first solution to this longstanding problem.

Findings

Stochastic noise induces hydrodynamic instability in shear flows.

Explains turbulence in astrophysical accretion disks.

Aligns with experimental and simulation observations.

Abstract

We provide the possible resolution for the century old problem of hydrodynamic shear flows, which are apparently stable in linear analysis but shown to be turbulent in astrophysically observed data and experiments. This mismatch is noticed in a variety of systems, from laboratory to astrophysical flows. There are so many uncountable attempts made so far to resolve this mismatch, beginning with the early work of Kelvin, Rayleigh, and Reynolds towards the end of the nineteenth century. Here we show that the presence of stochastic noise, whose inevitable presence should not be neglected in the stability analysis of shear flows, leads to pure hydrodynamic linear instability therein. This explains the origin of turbulence, which has been observed/interpreted in astrophysical accretion disks, laboratory experiments and direct numerical simulations. This is, to the best of our knowledge, the first solution to the long standing problem of hydrodynamic instability of Rayleigh stable flows.