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arXiv · 2504.03545

Passive scalar dispersion along porous stratum with natural convection

Chenglong Hu·Ke Xu·Yantao Yang
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Abstract

We investigate horizontal dispersion of a passive scalar in a porous stratum with Rayleigh-Darcy convection initiated by a geothermal gradient. While increasing Rayleigh number ($Ra$) keeps enhancing convection, the horizontal dispersion coefficient ($\hat{D}$) only scales with Ra in a narrow range, and saturates at $Ra \gtrsim 2500$. We rationalize this two-stage behavior: at low Ra, passive scalar migrates through bulk circumflex; at high Ra, boundary micro-plume layer becomes the dominant scalar pathway. Theory gives saturate $\hat{D}$ value proportional to the Lewis number $Le$ and molecular diffusivity $D_0$.

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Chenglong Hu, Ke Xu, Yantao Yang. 2025-04-04. Passive scalar dispersion along porous stratum with natural convection. https://arxiv.org/abs/2504.03545

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