arXiv subjects

Mrinal Jyoti Powdel

Publications and source records attributed to Mrinal Jyoti Powdel.

3 recordsLinked to original sources

arXiv2026

Dean-Kawasaki fluctuating hydrodynamics for backscattering hard rods

We study a system of backscattering hard rods in one dimension. Contrary to the usual ballistic hard rods, these hard rods flip the sign of their velocities with a rate $γ$. This leads to the decay of the odd moments of velocity while preserving the even moments: the number of conserved quantities in the system becomes half. The introduction of the flipping rate $γ$ is an integrability-breaking perturbation, and this leads to a change in the transport properties in the system. We show using a Dean-Kawasaki fluctuating hydrodynamic formulation that the unequal space-time correlation of the normal mode phase space densities attains a diffusive form at late times. Also, we show that for $t \gg 1/γ$, the two-time density-density correlation of mass densities spreads in a diffusive manner, and for $t \ll 1/γ$, the correlation spreads ballistically, for a background state given by the Boltzmann distribution. Our results present an elegant framework to study systems where integrability is broken by a stochastic noise.

cond-mat.stat-mech↗

arXiv2025

Uncertainty Growth in Stably Stratified Turbulence

We investigate uncertainty growth and chaotic dynamics in statistically steady, stably stratified three-dimensional turbulence. Using direct numerical simulations of the Boussinesq equations, we quantify the divergence of initially infinitesimal perturbations via twin simulations and decorrelator diagnostics. At short times, perturbations exhibit exponential growth, allowing us to define a (largest) Lyapunov exponent. We systematically examine how this exponent depends on stratification strength, quantified by the Brunt--Väisälä frequency and the Froude number, in a parameter regime relevant to oceanic flows. We find that increasing stratification leads to a monotonic reduction of the Lyapunov exponent, indicating suppressed chaoticity. Despite this reduction, uncertainty growth retains the universal temporal sequence observed in homogeneous isotropic turbulence -- initial decay, exponential growth, and saturation. The growth phase is characterized by self-similar decorrelator spectra, but exhibits strong anisotropy: uncertainty spreads much more slowly along the stratification direction than horizontally, with the disparity increasing with stratification strength. An analysis of the decorrelator evolution equation reveals that the suppression of chaos arises primarily from strain-mediated alignment dynamics rather than direct buoyancy coupling. Our results provide a quantitative characterization of predictability and uncertainty growth in stratified turbulence and highlight the utility of decorrelator-based methods for anisotropic geophysical flows.

physics.flu-dyn↗

arXiv2024

Conserved densities of hard rods: microscopic to hydrodynamic solutions

We consider a system of many hard rods moving in one dimension. As it is an integrable system, it possesses an extensive number of conserved quantities and its evolution on macroscopic scale can be described by generalised hydrodynamics. Using a microscopic approach, we compute the evolution of the conserved densities starting from non-equilibrium initial conditions of both quenched and annealed type. In addition to getting reduced to the Euler solutions of the hydrodynamics in the thermodynamic limit, the microscopic solutions can also capture effects of the Navier-Stokes terms and thus go beyond the Euler solutions. We demonstrate this feature from microscopic analysis and numerical solution of the Navier-Stokes equation in two problems -- first, tracer diffusion in a background of hard rods and second, the evolution from a domain wall initial condition in which the velocity distribution of the rods are different on the two sides of the interface. We supplement our analytical results using extensive numerical simulations.

cond-mat.stat-mech↗