Turbulent Rayleigh-Benard convection with polymers

Abstract eng:
We study the effects of polymers on heat transport in turbulent Rayleigh-B´enard convection using direct numerical simulations. We find that for small Weissenberg number, which is the ratio of the polymer relaxation time to the typical time scale of the flow, heat transport is reduced but for sufficiently large Weissenberg number, heat transport is enhanced. Our generalization of the classical boundary layer theory to flows with polymers has demonstrated that polymer stretching gives rise to a space-dependent effective viscosity. By carrying out the generalized boundary layer analysis using the effective viscosity profile computed from the numerical data, we provide a theoretical explanation of the observed transition of heat reduction to heat enhancement when Weissenberg number is increased.

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