Effect of aspect ratio on transverse diffusive broadening: A lattice Boltzmann study
Effect of aspect ratio on transverse diffusive broadening: A lattice Boltzmann study
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DOI：
10.1103/physreve.80.016304
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发表时间：
2009-07-01
影响因子：
2.4
通讯作者：
Raabe, D.
中科院分区：
文献类型：
--
作者：
Ayodele, S. G.;Varnik, F.;Raabe, D.
利用晶格玻尔兹曼方法研究了y型层流微混合器中两种并排流动的混相流体间扩散区的标度规律。晶格玻尔兹曼方法求解了耦合的三维流体力学和传质方程，并结合了与该问题相关的三维流动的固有特征。我们观察到不同的幂律状态发生在通道中心和靠近顶/底壁。扩散区的范围与通道中心轴向距离的平方根成正比。在顶部/底部壁上，我们发现在Ismagilov等人的实验中观察到的混合早期阶段的指数为1/3。理论物理。[j].科学通报，2004(2)。当距离入口较大时，靠近壁面的结垢指数变为1/2 [j - b]。萨蒙和A.阿贾里，J.阿普尔。物理学报，2009,27(2):481 - 481。在这里，我们重点研究了有限宽高比对扩散展宽的影响。有趣的是，我们发现无论通道的宽高比如何，缩放定律都是相同的。然而，表征顶/底壁加宽的指数1/3在下游恢复正常扩散行为的点在很大程度上取决于展弦比。我们提出了一种解释这一观察在侧面墙的剪切率。给出了对扩散展宽有不可忽略影响的宽高比范围的判据。
We study scaling laws characterizing the interdiffusive zone between two miscible fluids flowing side by side in a Y-shape laminar micromixer using the lattice Boltzmann method. The lattice Boltzmann method solves the coupled three-dimensional (3D) hydrodynamics and mass transfer equations and incorporates intrinsic features of 3D flows related to this problem. We observe the different power-law regimes occurring at the center of the channel and close to the top/bottom wall. The extent of the interdiffusive zone scales as the square root of the axial distance at the center of the channel. At the top/bottom wall, we find an exponent 1/3 at early stages of mixing as observed in the experiments of Ismagilov et al. [Appl. Phys. Lett. 76, 2376 (2000)]. At a larger distance from the entrance, the scaling exponent close to the walls changes to 1/2 [J.-B. Salmon and A. Adjari, J. Appl. Phys. 101, 074902 (2007)]. Here, we focus on the effect of the finite aspect ratio on diffusive broadening. Interestingly, we find the same scaling laws regardless of the channel's aspect ratio. However, the point at which the exponent 1/3 characterizing the broadening at the top/bottom wall reverts to the normal diffusive behavior downstream strongly depends on the aspect ratio. We propose an interpretation of this observation in terms of the shear rate at the side walls. A criterion for the range of aspect ratios with non-negligible effect on diffusive broadening is also provided.