Numerical Simulation And Experimental Study Of Micromixers Based On Chaotic Convection

Miniaturization and integration are great tendency for microfluidic system with the rapid development of MEMS.More and more attentions of researchers in research organizations and universities all over the world on micromixer gave rise to recently in the field of biology,chemistry,medicine,fluid,electronics,materials and machinery.In this paper,computational fluid dynamics,micro fluid mechanics and chaos theory as the theoretical basis,design of three layered integrated passive micromixers and an active micromixer of inlet velocity fluctuation.Mixing mechanism,mixing effect were analyzed through numerical simulation and experimental study methods,specific research contents and the conclusions are as follows:Firstly,comprehensive reviews on the passive and active micromixers were conducted.The advantages and disadvantages(i.e.mixing efficiency)of various micromixers were analyzed.It is concluded that,most of the micromixer have a good mixing performance only at a higher Reynolds number(more than 10~100),and it is always problematical when at lower Reynolds numbers(0.01~10)because only diffusion between two fluids can be depended.This is why we attend to study novel chaotic micromixer.Secondly,the characteristics and assumptions of micromechanics were introduced on the basis of basic equations of fluid mechanics.And then the mixing mechanism of various fluids in microchannel are analyzed,the mixing index to measure mixing performance was drawn into.The effective approach to enhance mixing performance at lower Reynolds number was proposed based on mixing theory of microfluidic.That is,the mixing performance can be improved by increasing the interfacial area between two fluids caused by chaotic advection.Thirdly,three kinds of passive micromixers including Helical micromixer,Smale micromixer and Baker micromixer were constructed based on the theory of chaotic mixing.Numerical simulations for mixing mechanism,influence factors on the mixing performance and pressure drop were carried out.The results showed that the mixing effect of Baker was the best in the lower Reynolds number,Smale was the second,and the Helical was the worst.Moreover,an active micromixer with a contraction-expansion channel was designed to load a sinusoidal fluctuation inlet velocity.The mixing performance of such a micromixer was analyzed by numerical simulations after secondary development by Fluent-UDF.It's concluded that the phase difference of 180 °,speed ratio of 2,St number in 0.2~0.4 mixing effect is best.Finally,the experiments for micromixer were conducted to measure the mixing performance by building an experimental platform.The comparisons of experimental results and numerical results shows us good agreement,the validity of present numerical model is qualitatively verified.