Numerical Study on the Characteristics of Boger Type Viscoelastic Fluid Flow in a Micro Cross-Slot under Sinusoidal Stimulation.
Numerical Study on the Characteristics of Boger Type Viscoelastic Fluid Flow in a Micro Cross-Slot under Sinusoidal Stimulation.
复制标题
正弦波激励下微十字槽内Boger型粘弹性流体流动特性数值研究
DOI：
10.3390/e22010064
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发表时间：
2020-01-03
期刊：
影响因子：
--
通讯作者：
Li FC
中科院分区：
文献类型：
--
作者：
Yuan C;Zhang HN;Chen LX;Zhao JL;Li XB;Li FC
十字槽几何形状在粘弹性流体非线性效应的研究中起着重要的作用。粘弹性流体在大通道深宽比（AR）微横缝中的流动可分为三种类型：对称流动、稳态非对称流动和恒速入口条件下的时间相关流动。然而，粘弹性流体在十字槽的流动模式时，在入口处施加刺激已经很少报道。本文通过对一个二维模型的数值模拟，研究了横缝流动在外部正弦激励下的响应。在定流速条件下，随着Weissenberg数Wi的增加，连续出现三种不同的流型。对于正弦变化的入口速度情况，当激励频率远离粘弹性流体的固有频率时，速度脉动场的频谱呈现出一个基频和多个谐波的特征。然而，当激励频率接近粘弹性流体的固有频率时，谐波频率消失。流态具有空间对称性，并随时间变化。结果表明，外部激励对粘弹性流体在二维微横缝通道中的流动形态产生影响，当激励频率接近流体的固有频率时，流体发生共振。
The cross-slot geometry plays an important role in the study of nonlinear effects of viscoelastic fluids. The flow of viscoelastic fluid in a micro cross-slot with a high channel aspect ratio (AR, the ratio of channel depth to width) can be divided into three types, which are symmetric flow, steady-state asymmetric flow and time-dependent flow under the inlet condition with a constant velocity. However, the flow pattern of a viscoelastic fluid in the cross-slot when a stimulation is applied at inlets has been rarely reported. In this paper, the response of cross-slot flow under an external sinusoidal stimulation is studied by numerical simulations of a two-dimensional model representing the geometry with a maximum limit of AR. For the cases under constant inlet velocity conditions, three different flow patterns occur successively with the increase of Weissenberg number (Wi). For the cases under sinusoidal varying inlet velocity conditions, when the stimulation frequency is far away from the natural frequency of a viscoelastic fluid, the frequency spectrum of velocity fluctuation field shows the characteristics of a fundamental frequency and several harmonics. However, the harmonic frequency disappears when the stimulation frequency is close to the natural frequency of the viscoelastic fluid. Besides, the flow pattern shows spatial symmetry and changes with time. In conclusion, the external stimulation has an effect on the flow pattern of viscoelastic fluid in the 2D micro cross-slot channel, and a resonance occurs when the stimulation frequency is close to the natural frequency of the fluid.
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