The Study On The Flow Characteristics Of Maxwell Fluid With High Zeta Potential In Parallel And Annular Micropipes

With the rapid development of microelectronics technology,the research and ap-plication of microfluidic devices have gotten more and more attention from scholars.It has a very important application in the field of microelectronics and biosensors,such as lab on a chip(lab-on-a-chip)and so on.At the same time,the problem of microfluidic transport has gradually come into people 's field of vision.Microfluidic systems themselves have special microscale effects,and movement of fluids in them can be achieved by different means according to their different effects,and electroosmotic flow driven by an external electric field in them has the advantages of easy control and high efficiency,so they have been widely used in the fields of biology,energy,engineering,medicine,etc.In this thesis,the periodic electroosmotic flow of Maxwell fluids in parallel mi-crochannel and annular microchannel under high Zeta potential is studied,and three cases are considered,which are the parallel microchannel under external AC elec-tric field,the annular microchannel under external DC electric field and the annular microchannel under external AC electric fie ld,respectively.Firstly,the nonlinear Poisson Boltzmann equation,Cauchy momentum equation and generalized Maxwell constitutive equation are solved through the finite difference method,and the potential distribution and the corresponding velocity distribution are given.Secondly,based on selected parameters related to physical properties,the speed distribution profile im-ages are plotted and analyzed.Finally,the similarities and differences of the velocity distribution for Maxwell fluid under low Zeta potential and high Zeta potential are discussed.The results show that wall Zeta potential,the dimensionless electric width K,Zeta potential ratio ?,inner and outer radius ratio a,oscillating Reynolds number Re,and relaxation time ?1? have some influence on the flow velocity of the fluid.The specific results are as follows:(1)With the increase of Zeta potential on the wall,the Maxwell fluid velocity in the annular and parallel micropipes also increases.(2)With the increase of oscillatory Reynolds number,velocity profile of the periodic electroosmotic flow(EOF)vibrates rapidly and its amplitude decreases gradually;with the increase of relaxation time,the velocity profile of the periodic EOF vibrates more rapidly under the action of external DC electric field.(3)For the parallel microchan-nel under the action of AC electric field,pulsatile electroosmotic flow(PEOF)velocity distribution is completely symmetrical when the Zeta potential of the upper and lower plates are symmetrical,but the PEOF velocity distribution changes from completely symmetrical to completely antisymmetric when the Zeta potential of the upper and lower plates is antisymmetric.(4)For the circular microchannel under the action of AC electric field,when the inner radius approaches to the outer radius,it behaves like a parallel plate microchannel,so its velocity distribution is similar to that in the par-allel microchannel,but the velocity profile is not completely symmetrical.(5)When comparing the velocity distributions of Maxwell fluid under high Zeta potential and low Zeta potential,it is found that the velocity distribution trend is the same in both cases,but there is fluctuation for each value;the velocity for high Zeta potential is significantly higher than that for low Zeta potential near the pipe wall,and the larger the dimensionless electric width K,the smaller the fluctuation is near the pipe wall;as the oscillation Reynolds number Re increases,the velocity difference increases,and it shows an oscillating trend.