Numerical Simulation Of Mixing Characteristics Of Passive Micromixer

Microfluidic chip is a kind of the micro-analysis test equipment, which are combined with preparation, sampling, processing (filtering, dilution, mixing, Reaction) and separation of micro-sample, with micro-channel network structure and other functional modules produced by Micro-machining on several square centimeter size's substrates. Microfluidic chip has a great advantage of high speed, highly effective and the low consumption. Diffusion and mixing are effectively controlled can enhance the efficiency of chemistry and the biological analysis, which have the very vital significance in extensive application of microfluidic chip. Micromixer is an important component of microfluidic chip, performances of which are determined by mixed-ability of micromixer. There are many factors which affect the mixing of microfluidic, such as the inlet velocity, diffusion coefficient, depth-width ratio, and so on. In this thesis three type micromixer had been investigated by using CFD(computational fluid dynamics) methods, respectively.In the study of Y-shaped micromixer of straight channel, the inlet velocity and diffusion coefficient have tremendous influence on mixing of fluid. With the increase of inlet velocity and diffusion coefficient, the mixing effects of two kind of liquid gradually worsen. The inlet angle has a certain influence to the mixing, but affects is small. With the depth-width ratio increased, its mixing performance gradually increased, but when H/W>=1, variation of H/W has a small influence on Y-shaped micromixers' mixing performance.For the Z-shaped micro-channel micromixer by convective mass transfer, the inlet velocity has the very tremendous influence to the mixing, but the diffusion coefficient's impact is small to the mixing. Micromixer with S/W=2 structure can make the good mixing performance under each kind of speed condition. The smaller the angle of corner of Z-shaped micro-channel micromixer is, the higher the mixing performance is. With the depth-width ratio increased, its mixing performance gradually increased, but when H/W>=0.6, variation of H/W has no influence on Y-shaped micromixers' mixing performance.Internal ribbed micromixer had been investigated by using numerical simulation methods. The results showed that: the inlet velocity has the very tremendous influence to the mixing, but the diffusion coefficient's impact is small to the mixing. The bigger the W1 is, the bigger the vortex intensity is, the higher the mixing performance of Internal ribbed micromixer is. With the increase of P/W ratio, the micromixer mixing performance are improved. With the depth-width ratio increased, its mixing performance gradually increased, but when H/W>=0.6, variation of H/W has no influence on Y-shaped micromixers' mixing performance.Mixing performance of three type of micromixer had been compared. The results showed that: Mixing performance of internal ribbed micromixer is superior to the other two Micromixer. In the analysis of the pressure loss, the bigger Flow is, the bigger the pressure loss is. Pressure loss of internal ribbed micromixer is biggest among three type of micromixer, followed by the pressure loss of Z-shaped micro-channel micromixer.In a word, influence law of the structural parameters of three type of micromixer to liquid mixing had been investigated, which has an instructive significance to optimum design and application of micromixer.