author={Sujit Kumar Nath and Banibrata Mukhopadhyay},
  journal={The Astrophysical Journal},
We provide a 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 toward the end of the nineteenth century. Here we show… 

Hydrodynamical transport of angular momentum in accretion disks in the presence of nonlinear perturbations due to noise

The origin of hydrodynamical instability and turbulence in the Keplerian accretion disk is a long-standing puzzle. The flow therein is linearly stable. Here we explore the evolution of perturbation

Hydrodynamical instability with noise in the Keplerian accretion discs: modified Landau equation

Origin of hydrodynamical instability and turbulence in the Keplerian accretion disc as well as similar laboratory shear flows, e.g. plane Couette flow, is a long-standing puzzle. These flows are

Origin of hydrodynamic instability from noise: From laboratory flow to accretion disk

We attempt to address the old problem of plane shear flows: the origin of turbulence and hence transport of angular momentum in accretion flows as well as laboratory flows, such as plane Couette

The competition between the hydrodynamic instability from noise and magnetorotational instability in the Keplerian disks

We venture for the comparison between growth rates for magnetorotational instability (MRI) and hydrodynamics instability in the presence of an extra force in the local Keplerian accretion flow. The

PT -symmetric spectral singularity and negative-frequency resonance

Vacuum consists of a bath of balanced and symmetric positive and negative frequency fluctuations. Media in relative motion or accelerated observers can break this symmetry and preferentially amplify

Spinning Black Holes, Spinning Flows and Spinors

Angular momentum is an indispensable quantity perhaps in describing all the astrophysical phenomena. This is because all the cosmic objects are expected to be rotating, however be the magnitude of



Bypass to Turbulence in Hydrodynamic Accretion: Lagrangian Analysis of Energy Growth

Despite observational evidence for cold neutral astrophysical accretion disks, the viscous process that may drive the accretion in such systems is not yet understood. While molecular viscosity is too

Stochastically driven instability in rotating shear flows

The origin of hydrodynamic turbulence in rotating shear flows is investigated, with particular emphasis on the flows whose angular velocity decreases but whose specific angular momentum increases

Magnetohydrodynamic stability of stochastically driven accretion flows.

It is found that such stochastically driven flows exhibit large temporal and spatial autocorrelations and cross-correlations of perturbation and, hence, large energy dissipations of perturgation, which generate instability.

Local Hydrodynamic Stability of Accretion Disks

We employ a variety of numerical simulations in the local shearing box system to investigate in greater depth the local hydrodynamic stability of Keplerian differential rotation. In particular, we

Bypass to Turbulence in Hydrodynamic Accretion Disks: An Eigenvalue Approach

Cold accretion disks with temperatures below ~3000 K are likely to be composed of highly neutral gas. The magnetorotational instability may cease to operate in such disks, so it is of interest to

On the relevance of subcritical hydrodynamic turbulence to accretion disk transport

Hydrodynamic unstratified Keplerian flows are known to be linearly stable at all Reynolds numbers, but may nevertheless become turbulent through nonlinear mechanisms. However, in the last ten years,

A hydrodynamic shear instability in stratified disks

We discuss the possibility that astrophysical accretion disks are dynamically unstable to non-axisymmetric distur- bances with characteristic scales much smaller than the vertical scale height. The

Particle dynamics in discs with turbulence generated by the vertical shear instability

Among the candidates for generating turbulence in accretion discs in situations with low intrinsic ionization the vertical shear instability (VSI) has become an interesting candidate, as it relies

Origin of nonlinearity and plausible turbulence by hydromagnetic transient growth in accretion disks: Faster growth rate than magnetorotational instability.

The results prove explicitly that the flows with a high Reynolds number (Re), which is the case for realistic astrophysical accretion disks, exhibit nonlinearity via TG of perturbation modes faster than that by modes producing MRI.

Stability and turbulent transport in Taylor-Couette flow from analysis of experimental data

This paper provides a prescription for the turbulent viscosity in rotating shear flows for use e.g. in geophysical and astrophysical contexts. This prescription is the result of the detailed analysis