Two-layer Thermally Driven Turbulence: Mechanisms for Interface Breakup

Abstract

It is commonly accepted that the breakup criteria of drops or bubbles in turbulence is governed by surface tension and inertia. However, also {\it{buoyancy}} can play an important role at breakup. In order to better understand this role, here we numerically study Rayleigh-Bénard convection for two immiscible fluid layers, in order to identify the effects of buoyancy on interface breakup. We explore the parameter space spanned by the Weber number $5\le We\le 5000$ (the ratio of inertia to surface tension) and the density ratio between the two fluids $0.001\le \Lambda \le 1$, at fixed Rayleigh number $Ra=10^8$ and Prandtl number $Pr=1$. At low $We$, the interface undulates due to plumes. When $We$ is larger than a critical value, the interface eventually breaks up. Depending on $\Lambda$, two breakup types are observed: The first type occurs at small $\Lambda \ll 1$ (e.g. air-water systems) when local filament thicknesses exceed the Hinze length scale. The second, strikingly different, type occurs at large $\Lambda$ with roughly $0.5<\Lambda \le 1$ (e.g. oil-water systems): The layers undergo a periodic overturning caused by buoyancy overwhelming surface tension. For both types the breakup criteria can be derived from force balance arguments and show good agreement with the numerical results.

arXiv comment13 pages, 7 figures

References in corpus (11)

• Large scale dynamics in turbulent Rayleigh-Benard convection
• Extended lifetime of respiratory droplets in a turbulent vapour puff and its implications on airborne disease transmission
• Comparison between two and three dimensional Rayleigh-Bénard convection
• Transition to the ultimate regime in two-dimensional Rayleigh-Bénard convection
• Turbulent thermal superstructures in Rayleigh-Bénard convection
• Droplet size distribution in homogeneous isotropic turbulence
• Droplet-turbulence interactions and quasi-equilibrium dynamics in turbulent emulsions
• Multiple states in turbulent large-aspect ratio thermal convection: What determines the number of convection rolls?
• Droplets in homogeneous shear turbulence
• Flow organization and heat transfer in turbulent wall sheared thermal convection
• Wall roughness induces asymptotic ultimate turbulence

Cited by in corpus (1)

• Regime transitions in thermally driven high-Rayleigh number vertical convection