High frequency oscillatory flow in micro channels
High frequency oscillatory flow in micro channels
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DOI：
10.1016/j.colsurfa.2014.03.062
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发表时间：
2014-10
期刊：
影响因子：
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通讯作者：
M. Karbaschi;A. Javadi;Dariush Bastani;Reinhard Miller
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文献类型：
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作者：
M. Karbaschi;A. Javadi;Dariush Bastani;Reinhard Miller
本文采用基于毛细压力技术的振荡滴泡分析仪（ODBA）对100 Hz以内的高频振荡流动进行了计算和实验研究。结合压力幅值实验数据，对CFD计算结果进行了验证。所产生的振荡流与随之产生的压力幅值之间相移的模拟结果也与实验数据吻合较好。在没有任何可压缩性和粘弹性效应和假设的情况下，振荡期间的复杂速度场是观测相移的主要原因。最大瞬时流量时刻的速度分布结果表明，在低频时叶尖内的规则抛物层流过渡到中高频时的复杂流动。对于最大压力幅值矩，观察到具有三重最大/最小速度区域的复杂形状。速度剖面形状的演变主要取决于频率和毛细尖端的大小，而不是体积振幅。结果与水动力松弛时间的概念有很好的相关性，但所提出的方法揭示了更多的细节。在尖端内部产生双抛物线状流动，可以定义为流体流过更小的管道或通道，这是观察到最大压力损失的主要原因，并且具有一定的相移到最大瞬时液体流量。
This paper deals with computational and experimental studies on the oscillatory flow at high frequencies up to 100 Hz performed with the Oscillating Drop and Bubble Analyzer (ODBA) setup based on the capillary pressure technique. The CFD results are validated considering pressure amplitude experimental data. The simulated results of phase shift between the generated oscillatory flow and the consequent pressure amplitudes show also good agreement with the experimental data. In absence of any compressibility and viscoelasticity effects and assumptions, a complex velocity field during oscillation is the main reason for the observation of a phase shift. The results of velocity profiles at the moment of maximum instant flow rate illustrate a transient of the regular parabolic laminar flow inside the tip at low frequencies to a complex flow profile at intermediate and high frequencies. For the moment of maximum pressure amplitude a complex shape with triple maximum/minimum velocity regions is observed. The evolution of the velocity profile shape depends significantly on the frequency and capillary tip size, however, not by the volume amplitude. The results are in good correlation with the concept of the hydrodynamic relaxation time, however, the presented approach reveals more details. The creation of a double parabolic-like flow inside the tip, which can be defined as fluid flow through much smaller tubes or channels is the main reason for observing a maximum pressure loss with a certain phase shift to the maximum instant liquid flow rate.