Department of Chemical Engineering, IIT Madras, Chennai 600036, India.
Phys Rev E. 2017 Sep;96(3-1):033117. doi: 10.1103/PhysRevE.96.033117. Epub 2017 Sep 29.
We propose an innovative mechanism for enhancing mixing in steady pressure driven flow of an electrolytic solution in a straight rectangular microchannel. A transverse electric field is used to generate an electroosmotic flow across the cross-section. The resulting flow field consists of a pair of helical vortices that transport fluid elements along the channel. We show, through numerical simulations, that chaotic advection may be induced by periodically varying the direction of the applied electric field along the channel length. This periodic electric field generates a longitudinally varying, three-dimensional steady flow, such that the streamlines in the first half of the repeating unit cell intersect those in the second half, when projected onto the cross-section. Mixing is qualitatively characterized by tracking passive particles and obtaining Poincaré maps. For quantification of the extent of mixing, Shannon entropy is calculated using particle advection of a binary mixture. The convection diffusion equation is also used to track the evolution of a scalar species and quantify the mixing efficiency as a function of the Péclet number.
我们提出了一种在直矩形微通道中稳定压力驱动的电解液混合的创新机制。横向电场用于在横截面上产生电渗流。所产生的流场由一对螺旋涡旋组成，它们沿着通道输送流体质点。通过数值模拟，我们表明可以通过沿通道长度周期性地改变施加电场的方向来诱导混沌对流。这种周期性的电场产生了一个沿纵向变化的三维稳定流，使得在重复单元的前一半中的流线与在后一半中的流线相交，当它们投影到横截面上时。通过跟踪被动粒子并获得庞加莱映射来定性地描述混合。为了量化混合的程度，使用二进制混合物的粒子平流来计算香农熵。还使用对流扩散方程来跟踪标量物种的演化，并将混合效率作为佩克莱数的函数进行量化。
