Design Of Micromixer Based On Eulerian And Lagrangian Description

As a key component of microfluidic device, micromixer is widely applied inmicrofluidic systems. This thesis focuses on the topology optimization design ofmicromixer based on the improved optimization model. Especially, Eulerian andLagrangian description were used respectively to modeling and designing thecharacteristic layout of micromixers.Based on the results of previous studies, this thesis mainly focuses on furtherimprovement of the micromixer systematic design and evaluation methods：(1) Inorder to avoid the numerical unstable and permeable problem when usingincompressible NS-Darcy equations, a relaxation condition which makes thesolid-phase slightly compressible is proposed. It can effectively solve the infiltrationproblems in fluid topology optimization. Therefore, the mixing effect designed byEulerian description is improved obviously.(2) Combined with the Lagrangianmapping method and topology optimization, the design the micromixer underLagrangian description is implemented. The artificial diffusion was avoided whensolving the convection-diffusion equations numerically. And this research gives alower limit on the evaluation method of mixing.Finally, the slightly compressible Navier-Stokes equations are applied to designno-moving-parts micro-Tesla-type valves. Valve effect was significantly better thanthe previous structures. Optimized results demonstrate the better permeabilitycontrol of the improved model. A topology optimization model under Eulerian was established to design micromixer. And a benchmark example of three-dimensionalbend micromixer was given too. Through examples of straight pipe mixer, thevalidity of optimization model, which combines with slightly compressibleNavier-Stokes equations with Lagrangian mapping method for designingmicromixer, is proved.