Multi-particle-collision simulation of heat transfer in low-dimensional fluids

Abstract

Simulation of transport properties of confined, low-dimensional fluids can be performed efficiently by means of Multi-Particle Collision (MPC) dynamics with suitable thermal-wall boundary conditions. We illustrate the effectiveness of the method by studying dimensionality effects and size-dependence of thermal conduction, properties of crucial importance for understanding heat transfer at the micro-nanoscale. We provide a sound numerical evidence that the simple MPC fluid displays the features previously predicted from hydrodynamics of lattice systems: (1) in 1D, the thermal conductivity $κ$ diverges with the system size $L$ as $κ\sim L^{1/3}$ and its total heat current autocorrelation function $C(t)$ decays with the time $t$ as $C(t)\sim t^{-2/3}$; (2) in 2D, $κ$ diverges with $L$ as $κ\sim \mathrm{ln} (L)$ and its $C(t)$ decays with $t$ as $C(t)\sim t^{-1}$; (3) in 3D, its $κ$ is independent with $L$ and its $C(t)$ decays with $t$ as $C(t)\sim t^{-3/2}$. For weak interaction (the nearly integrable case) in 1D and 2D, there exists an intermediate regime of sizes where kinetic effects dominate and transport is diffusive before crossing over to expected anomalous regime. The crossover can be studied by decomposing the heat current in two contributions, which allows for a very accurate test of the predictions. In addition, we also show that upon increasing the aspect ratio of the system, there exists a dimensional crossover from 2D or 3D dimensional behavior to the 1D one. Finally, we show that an applied magnetic field renders the transport normal, indicating that pseudomomentum conservation is not sufficient for the anomalous heat conduction behavior to occur.