Numerical study of double-diffusive sedimentation in thermally stratified fluid

Hung, Chen-Yen; Niu, Yang-Yao; Chou, Yu‐Min

doi:10.1017/jfm.2020.223

Cited by 6 publications

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References 60 publications

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“…8(c, d)] and exploring the effects of background temperature or salinity gradients on the particle-induced instabilities. 17,18,37,38 Problems involving complex fluids, such as fine tailings 39 , are also of practical interest and worthy of future investigations.…”

Section: Discussionmentioning

confidence: 99%

Evolution of Rayleigh−Taylor instability at the interface between a granular suspension and a clear fluid

2022

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We report the characteristics of Rayleigh-Taylor instabilities (RTI) occurring at the interface between a suspension of granular particles and a clear fluid. The time evolution of these instabilities is studied numerically using coupled lattice Boltzmann and discrete element methods with a focus on the overall growth rate (σ) of the instabilities and their average wave number (k). Special attention is paid to the effects of two parameters, the solid fraction (0.10{less than or equal to}φ{less than or equal to}0.40) of the granular suspension and the solid-to-fluid density ratio (1.5{less than or equal to}R{less than or equal to}2.7). Perturbations at the interface are observed to undergo a period of linear growth, the duration of which decreases with φ and scales with the particle shear time d/w∞, where d is the particle diameter and w∞ is the terminal velocity. For φ>0.10, the transition from linear to nonlinear growth occurs when the characteristic steepness of the perturbations is around 29%. At this transition, the average wave number is approximately 0.67d-1 for φ>0.10 and appears independent of R. For a given φ, the growth rate is found to be inversely proportional to the particle shear time, i.e., σ ∝(d/w∞)-1; at a given R, σ increases monotonically with φ, largely consistent with a linear stability analysis (LSA) in which the granular suspension is approximated as a continuum. These results reveal the relevance of the time scale d/w∞ to the evolution of interfacial granular RTI, highlight the various effects of φ and R on these instabilities, and demonstrate modest applicability of the continuum-based LSA for the particle-laden problem.

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