基于三临界螺旋涡不稳定性的微流体混合
Enhanced Microfluidic Mixing via a Tricritical Spiral Vortex Instability
摘要：
实验测量和数值模拟的流体流动通过交叉槽装置的纵横比（深度：宽度）的范围内，0.4 <α < 3.87。对于低雷诺数Re，流动是对称的，并且从相反方向进入交叉槽的流体流之间存在尖锐的边界。当Re_c大于某一α值时，流场发生分叉（但仍为定常层流），并在出流通道中心轴附近形成螺旋涡结构。表征不稳定性的序参量按照六阶朗道势增长，并随着α的增加显示出从二阶到一阶的过渡。当α = 0.55时出现三临界点。螺旋涡流在流场中起到混合区域的作用，这种现象可以用来驱动微流体装置中的增强混合。
英文摘要：
Experimental measurements and numerical simulations are made on fluid flow through cross-slot devices with a range of aspect (depth:width) ratios, 0.4 < alpha < 3.87. For low Reynolds numbers Re, the flow is symmetric and a sharp boundary exists between fluid streams entering the cross-slot from opposite directions. Above an alpha-dependent critical value Re_c, the flow undergoes a symmetry-breaking bifurcation (though remains steady and laminar) and a spiral vortex structure develops about the central axis of the outflow channel. An order parameter characterizing the instability grows according to a sixth-order Landau potential, and shows a progression from second order to first order transitions as alpha increases. A tricritical point occurs for alpha ~ 0.55. The spiral vortex acts as a mixing region in the flow field and this phenomenon can be used to drive enhanced mixing in microfluidic devices.
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