| Summary: | 碩士 === 崑山科技大學 === 機械工程研究所 === 93 === The rheological formula of the particles dispersed in carrier fluid can be deduced from microstructure-based models. This type of formula offers a convenient means to relate particle properties to macroscopic flow behavior. Non-Newtonian fluids are fluids which do not exhibit linear relationship between stress and the rate of strain. Fluids including suspensions of DNA, proteins, blood cells and sorts of polymeric compounds used in the industry are non-Newtonian in their nature. This paper presents an analysis, which uses a rheological model of suspension of deformable particles, to study the effects of particle concentration on tube flows, especially for flows through narrow tubes.
The beginning of formulating rheological behavior of microscopically heterogeneous fluids dates back to the celebrated work of Einstein in 1906. The model used in this paper is coined as the modified Goddard and Miller model. The Goddard and Miller model can be regarded as a deformable particle version of the Einstein model. The modified Goddard and Miller model, proposed by Pal recently, add the consideration of the hydrodynamic interactions between particles. A small modification is also
proposed in this paper, which is to introduce a phenomenological parameter to account for the elastic behavior of fluid. The elastic property of a fluid is related to strain while the viscous property is related to strain rate.
Reduction of particle concentration may occur when a particle suspension entering a capillary, this is referred to as skimming effect. Increase of pressure gradient abates the skimming effect. After a bifurcation, uneven particle concentration distribution between two branch tubes of different diameters is expected.
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