Lagrangian dynamics and heat transfer in porous media convection

TL;DR

This study uses pore-scale numerical simulations to analyze how porosity affects flow dynamics and heat transfer in porous media convection, revealing heterogeneous flow patterns and anomalous transport phenomena.

Contribution

It provides new insights into Lagrangian particle dynamics and heat transfer mechanisms in porous media, highlighting the impact of porosity on flow heterogeneity and transport properties.

Findings

Flow is highly heterogeneous with convection channels and stagnant regions.

Decreased porosity leads to anomalous long-time transport behavior.

Enhanced vertical velocity-temperature correlation improves heat transfer.

Abstract

We report a numerical study of Rayleigh--B\'enard convection through random porous media using pore-scale modelling, focusing on the Lagrangian dynamics of fluid particles and heat transfer for varied porosities $\phi$. Due to the interaction between the porous medium and the coherent flow structures, the flow is found to be highly heterogeneous, consisting of convection channels with strong flow strength and stagnant regions with low velocities. The modifications of flow field due to porous structure have a significant influence on the dynamics of fluid particles. Evaluation of the particle displacement along the trajectory reveals the emergence of anomalous transport for long times as $\phi$ is decreased, which is associated with the long-time correlation of Lagrangian velocity of the fluid. As porosity is decreased, the cross-correlation between the vertical velocity and temperature fluctuation is enhanced, which reveals a mechanism to enhance the heat transfer in porous media convection.