The configurations of a FENE bead-spring chain in transient rheological flows and in a turbulent flow

AIP Publishing - Tập 5 Số 4 - Trang 881-890 - 1993
H. Massah1, K. Kontomaris2, W. R. Schowalter3, Thomas J. Hanratty4
1♯2516 HSL, Department of Civil Engineering, University of Illinois, Urbana, Illinois 61801
2AMOCO Research Center, Naperville, Illinois 60566-7011
3♯119 RAL, Department of Chemical Engineering, University of Illinois, Urbana, Illinois 61801
4♯205 RAL, Department of Chemical Engineering, University of Illinois, Urbana, Illinois 61801

Tóm tắt

The changes in the configuration of a FENE bead-spring chain in a direct numerical simulation of turbulent channel flow and in some simple rheological flows are examined. Unraveling occurs both in uniaxial and shear flows, but the uniaxial flow is more effective. A vortex with a large rotation rate perpendicular to the principal strain of a uniaxial flow has only a minor retarding effect while a small rotation rate delays the unraveling substantially. In a turbulent flow, the chain unravels the most in the viscous sublayer, to about 90% of its fully extended length. It aligns at a 7° angle with the direction of mean flow. In the buffer zone, it unravels and coils up and takes different orientations at different times. Outside the wall region, the chain assumes a coiled configuration. The unraveling of the chain strongly depends on the relaxation time of the chain normalized with the wall shear rate, λ+. A value of λ+=10 exhibits strong unraveling while very weak unraveling is observed below λ+=1.

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Tài liệu tham khảo

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AIP Publishing

Tập 5 Số 4

881-890

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