Wed May 27th 2015
11:00 – 12:00
ZH286
Seminar Heat Transfer and Plume Dynamics in Highly Confined Rayleigh-Bénard Convection
Shi-Di Huang

Details:

The effects of geometrical confinement on turbulent Rayleigh-Bénard convection are investigated both experimentally and numerically. It is found that when the width of the convection cell is narrowed, the heat-transfer efficiency increases significantly (up to ~20% for the parameter range explored), despite the fact that the overall flow, i.e. the turbulent intensity, is reduced. This enhancement is brought about by the changes in the dynamics and morphology of the thermal plumes, which become more coherent and energetic as a result of confinement, thus are able to transport heat more efficiently. By examining the characterized scales of thermal plumes, a new paradigm for heat transport with universal behaviors is revealed. In this talk, I will show that the mean travelling spacing of the rod-like plumes defines the onset aspect ratio below which the convective flow enters the so-called plume-controlled regime. After the onset, the plume coherency is greatly increased and reaches an upper limit imposed by the system size and the sidewall boundary layers, and therefore an optimal aspect ratio exists, at which heat transfer enhancement is maximized. (This work is supported by the Hong Kong Research Grants Council under Grant No. CUHK 403712.)
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