Role of interfacial stabilization in the Rayleigh-Bénard convection of liquid-liquid dispersions

Abstract

Based on mesoscale lattice Boltzmann numerical simulations, we characterize the Rayleigh-Bénard (RB) convective dynamics of dispersions of liquid droplets in another liquid phase. Our numerical methodology allows us to modify the droplets' interfacial properties to mimic the presence of an emulsifier (e.g., a surfactant), resulting in a positive disjoining pressure that stabilizes the droplets against coalescence. To appreciate the effects of this interfacial stabilization on the RB convective dynamics, we carry out a comparative study between a proper emulsion, i.e., a system where the stabilization mechanism is present (stabilized liquid-liquid dispersion), and a system where the stabilization mechanism is absent (non-stabilized liquid-liquid dispersion). The study is conducted by systematically changing both the volume fraction, $\varphi$, and the Rayleigh number, Ra. We find that the morphology of the two systems is dramatically different due to the different interfacial properties. However, the two systems exhibit similar global heat transfer properties, expressed via the Nusselt number Nu. Significant differences in heat transfer emerge at smaller scales, which we analyze via the Nusselt number defined at mesoscales, Nu${}_{\mathrm{mes}}$. In particular, stabilized systems exhibit more intense mesoscale heat flux fluctuations due to the persistence of fluid velocity fluctuations down to small scales, which are instead dissipated in the interfacial dynamics of non-stabilized dispersions. For fixed Ra, the difference in mesoscale heat flux fluctuations depends non-trivially on $\varphi$, featuring a maximum in the range $0.1<\varphi <0.2$. Taken all together, our results highlight the role of interfacial physics in mesoscale convective heat transfer of complex fluids.

arXiv comment16 pages, 11 figures

References in corpus (27)

• Large scale dynamics in turbulent Rayleigh-Benard convection
• Yield Stress Materials in Soft Condensed Matter
• Thermal convection for large Prandtl numbers
• Generalized Lattice Boltzmann Method with multi-range pseudo-potential
• Radial boundary layer structure and Nusselt number in Rayleigh-Benard convection
• Flow reversals in thermally driven turbulence
• Convection in multiphase flows using Lattice Boltzmann methods
• Resolving the fine-scale structure in turbulent Rayleigh-Benard convection
• Mesoscopic lattice Boltzmann modeling of soft-glassy systems: theory and simulations
• Droplet size distribution in homogeneous isotropic turbulence
• Lagrangian temperature, velocity and local heat flux measurement in Rayleigh-Benard convection
• Heat transport in boiling turbulent Rayleigh-Bénard convection
• Spinodal decomposition in homogeneous and isotropic turbulence
• The emergence of supramolecular forces from lattice kinetic models of non ideal fluids: applications to the rheology of soft glassy meterials
• Heat transfer mechanisms in bubbly Rayleigh-Benard convection
• Hybrid Lattice Boltzmann/Finite Difference simulations of viscoelastic multicomponent flows in confined geometries
• Ductile-to-brittle transition and yielding in soft amorphous materials: perspectives and open questions
• Heat transfer in turbulent Rayleigh-Bénard convection within two immiscible fluid layers
• Enhancing Heat Transport in Multiphase Rayleigh-Bénard Turbulence by Changing the Plate-Liquid Contact Angles
• Metastability at the Yield-Stress Transition in Soft Glasses
• Rayleigh-Bénard convection of a model emulsion: anomalous heat-flux fluctuations and finite-size droplets effects
• Avalanche statistics during coarsening dynamics
• TLBfind: a Thermal Lattice Boltzmann code for concentrated emulsions with FINite-size Droplets
• Analysis of the heat transfer fluctuations in the Rayleigh-Bénard convection of concentrated emulsions with finite-size droplets
• On the impact of controlled wall roughness shape on the flow of a soft-material
• Build up of yield stress fluids via chaotic emulsification
• Intermittent thermal convection in jammed emulsions