Turbulent Bubble-Laden Channel Flow of Power-Law Fluids: A Direct Numerical Simulation Study
Turbulent Bubble-Laden Channel Flow of Power-Law Fluids: A Direct Numerical Simulation Study
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DOI：
10.3390/fluids6010040
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发表时间：
2021-01-01
期刊：
影响因子：
1.9
通讯作者：
Klein, Markus
中科院分区：
文献类型：
--
作者：
Braeuer, Felix;Trautner, Elias;Klein, Markus
本文研究了非牛顿流体行为对垂直槽道中含气泡湍流下降流流动统计特性的影响。对幂律指数分别为0.7（剪切变稀）、1（牛顿）和1.3（剪切增稠）的幂律流体在气相体积分数为6%时的液相流动进行了直接数值模拟研究。通过对应于摩擦雷诺数Re τ近似为127.3的恒定体积流率向下驱动流动。Eotvos数在Eo=0.3125和Eo=3.75之间变化，以研究准球形以及摆动气泡的影响，从而研究气泡变形性与液体体积的幂律行为的相互作用。得到的一阶和二阶流体统计，即，穿过通道的气体分数、平均速度和速度波动轮廓显示出响应于变化的幂律指数的明显趋势。此外，有人观察到，气泡的振荡增加，降低幂律指数。在通道的核心，气泡显着增加的耗散率，这与其在壁的行为，表现出类似的数量级的所有幂律指数。
The influence of non-Newtonian fluid behavior on the flow statistics of turbulent bubble-laden downflow in a vertical channel is investigated. A Direct Numerical Simulation (DNS) study is conducted for power-law fluids with power-law indexes of 0.7 (shear-thinning), 1 (Newtonian) and 1.3 (shear-thickening) in the liquid phase at a gas volume fraction of 6%. The flow is driven downward by a constant volumetric flow rate corresponding to a friction Reynolds number of Re tau approximate to 127.3. The Eotvos number is varied between Eo=0.3125 and Eo=3.75 in order to investigate the influence of quasi-spherical as well as wobbling bubbles and thus the interplay of the bubble deformability with the power-law behavior of the liquid bulk. The resulting first- and second-order fluid statistics, i.e., the gas fraction, mean velocity and velocity fluctuation profiles across the channel, show clear trends in reply to varying power-law indexes. In addition, it was observed that the bubble oscillations increase with decreasing power-law index. In the channel core, the bubbles significantly increase the dissipation rate, which, in contrast to its behavior at the wall, shows similar orders of magnitude for all power-law indexes.