Enhanced and reduced heat transport in turbulent thermal convection with polymer additives.
Enhanced and reduced heat transport in turbulent thermal convection with polymer additives.
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DOI：
10.1103/physreve.86.016325
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发表时间：
2011-11
期刊：
影响因子：
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通讯作者：
Ping Wei;R. Ni;K. Xia
中科院分区：
文献类型：
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作者：
Ping Wei;R. Ni;K. Xia
我们提出了一个实验研究的湍流Rayleigh-Bénard对流与聚合物添加剂中的两个对流池，一个具有光滑的顶部和底部的板和粗糙的顶部和底部的板。对于具有光滑板的电池，观察到测量的努塞尔数（Nu）的减少。此外，Nu降低的量随着聚合物浓度（c）的增加而增加，对于c = 120 ppm达到~12%，并且此后明显趋于平稳。然而，对于具有粗糙板的电池，当聚合物浓度大于120 ppm时，观察到Nu的增强（~4%）。当添加聚合物时，在相同单元中的增加的大规模循环（LSC）速度证实了Nu的这种增加。相比之下，光滑细胞中的LSC速度被发现基本上是相同的，有和没有聚合物。进一步发现，在光滑胞腔中，整体Nu的均方根值σ（Nu）和局部温度的均方根值σ（T）都表现出与Nu本身类似的对c的依赖性.与此相反，在粗糙胞腔中，σ（Nu）和σ（T）基本上与c无关.
We present an experimental study of turbulent Rayleigh-Bénard convection with polymer additives made in two convection cells, one with a smooth top and bottom plates and the other with a rough top and bottom plates. For the cell with smooth plates, a reduction of the measured Nusselt number (Nu) was observed. Furthermore, the amount of Nu reduction increases with increasing polymer concentration (c), reaching ~12% for c = 120 ppm and an apparent leveling off thereafter. For the cell with rough plates, however, an enhancement (~4%) of Nu was observed when the polymer concentration is greater than 120 ppm. This increase in Nu is corroborated by an increased large-scale circulation (LSC) velocity in the same cell when polymers are added. In contrast, the LSC velocity in the smooth cell is found to be essentially the same with and without polymers. It is further found that in the smooth cell the rms values of the global Nu, σ(Nu), and that of the local temperature, σ(T), both exhibit similar dependence on c as Nu itself. In contrast, σ(Nu) and σ(T) in the rough cell are found to be essentially independent of c.