Journal article
How rotational vortices enhance transfers
Physics of fluids (1994), Vol.25(9), 093301
09/2013
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Abstract
Inspired by recent observations of granular flow, we examine how rotational vortices contribute to heat or mass transfer enhancement in a fluid. We use a tracer method to simulate both diffusion and advection in systems of differing intrinsic diffusivities D-0, vortex sizes R, vortex rotation frequencies f, and vortex lifetimes l. The results reveal that these systems exhibit an effective diffusive behavior, characterized by an effective diffusivity D-eff. A striking finding is the existence of two regimes, dichotomised by the Peclet number Pe = R(2)f/D-0. When the Peclet number is less than one, there is no transfer enhancement, D-eff = D-0. For higher values, vortices produce some transfer enhancement with a corresponding power law D-eff/D-0 approximate to Pe(n). The power n ranges from a lower bound of 0.5 for stationary vortices of lifetime infinity, to an upper bound of 1 for vortices of lifetimes shorter than half a rotation. This difference is attributed to two different internal mechanisms involving the coupling of diffusion and advection. These results could provide new insights on the transfer properties of fluid systems comprising rotational vortices, such as granular materials, suspensions, foams, and emulsions, as well as low Reynolds number stirred flows.
Details
- Title
- How rotational vortices enhance transfers
- Creators
- D. Griffani - University of SydneyP. Rognon - Aix-Marseille UniversityB. Metzger - Aix-Marseille UniversityI. Einav - University of Sydney
- Publication Details
- Physics of fluids (1994), Vol.25(9), 093301
- Publisher
- Amer Inst Physics
- Number of pages
- 8
- Identifiers
- 991013179793502368
- Copyright
- (C) 2013 AIP Publishing LLC.
- Academic Unit
- Faculty of Science and Engineering; Engineering
- Language
- English
- Resource Type
- Journal article