On the heat transfer fluctuations in concentrated emulsions with finite-size droplets under Rayleigh-Bénard thermal convection

In this study, we utilize numerical simulations at the mesoscale to investigate the heat transfer mechanism in Rayleigh-Bénard convection of emulsions with finite-size droplets, specifically focusing on the regime just above the transition from conduction to thermal convection. In this regime, we observe anomalous fluctuations in heat transfer, which are attributed to the collective motion of droplets [1]. Employing the lattice Boltzmann TLBfind code [2], we present a comprehensive understanding of the correlation between macroscopic heat transfer fluctuations and droplet statistics at the mesoscale. Notably, we systematically increase the droplet concentration and examine the emergence of these fluctuations, alongside the segregation of "extreme events" within the boundary layers. Additionally, we conduct a statistical analysis involving droplet displacements to characterize the spatial extension (S) and duration (T) of coherent droplet motion associated with these extreme events. Our findings reveal that a power-law behavior in the probability distribution function of S and T is observed only for very high droplet concentrations, indicative of an avalanche-like behavior [3].

References

[1] F. Pelusi et al, Soft Matter 17(13), 3709 - 3721 (2021).

[2] F. Pelusi et al, Comp. Phys. Comm. 273, 108259 (2022).

[3] F. Pelusi et al, submitted paper arXiv:2306.02404v1