Effect of particle injection on heat transfer in rotating Rayleigh-Bénard convection

P.R. Joshi, H. Rajaei, R.P.J. Kunnen, H.J.H. Clercx

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Abstract

The present study attempts to change the regime transitions and heat transfer properties in rotating Rayleigh-Benard convection by injecting 100 µm diameter particles in the flow. The particles start settling out of the fluid immediately after injection, and separate entirely from the fluid over a period of several hours. The particles deposit on the top and bottom surfaces, forming porous layers with non-ideal thermal properties, and, as expected, decrease the heat flux. The
reduction in heat transfer is a result of the inability of the layers to respond rapidly enough to fluid temperature fluctuations. However, in the rotation-dominated geostrophic regime, the heat transfer normalized by its non-rotating value is higher in presence of the particle layers than without them. Direct numerical simulations with ideal heat transfer walls indicate that the temperature
fluctuations in the bulk become slower under the damping effect of rotation, in contrast with those in the boundary layers which do not show any damping until the flow transitions to the geostrophic regime. In this regime, the dominant time scale of the near-wall fluid temperature fluctuations increases substantially as the rotation rate is increased. It is thus likely that the time response of
the particle layers in relation to that of the nearby fluid improves only in the geostrophic regime, which is reflected in a relatively larger heat transfer.
Original languageEnglish
Article number084301
Number of pages19
JournalPhysical Review Fluids
Volume1
Issue number8
DOIs
Publication statusPublished - 2016

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