From Rayleigh-Bénard convection to porous-media convection: how porosity affects heat transfer and flow structure

Liu, S.; Jiang, L.; Chong, K.L.; Zhu, X.; Wan, Z.-H.; Verzicco, R.; Stevens, R.J.A.M.; Lohse, D.; Sun, C.

doi:10.1017/jfm.2020.309

Publication 64 · Thermal convection

From Rayleigh-Bénard convection to porous-media convection

S. Liu, L. Jiang, K.L. Chong, X. Zhu, Z.-H. Wan, R. Verzicco, R.J.A.M. Stevens, D. Lohse, C. Sun, J. Fluid Mech. 895, A18 (2020).

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Main finding

Moderate obstruction organizes convection and enhances heat transport before stronger blockage suppresses the flow in the simulated system. Transfer of the observed length-scale crossover to Darcy flow or three-dimensional systems remains a hypothesis.

Heat transport against porosity at two Rayleigh numbers, rising to a peak then falling — **How to read the figure.** Nusselt number normalised by its value in the unobstructed cell, against porosity, at two Rayleigh numbers. Transport rises above the unobstructed value as porosity falls, reaches a peak, then drops below it as the obstruction becomes stronger. Open the full-resolution figure. Figure 2. S. Liu et al. (2020). No separate licence is stated here; consult the original publication and credited source before reuse.

Why this matters

A moderate obstruction can organize transport before stronger blockage suppresses it.

Research context

Obstacles initially regularize temperature–velocity coupling and suppress counter-gradient transport, but their drag suppresses the flow at lower porosity. The crossover depends on the pore scale relative to the thermal boundary layer and is demonstrated only in the two-dimensional obstacle geometry studied here.

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