Interfacial stability and deformation of two stratified power law fluids in plane poiseuille flow Part II. Interface deformation

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Abstract

A numerical analysis of two immiscible fluids in two coextrusion sheet-forming geometries having either straight or converging channel downstreams has been conducted. Numerical computations were carriedout for both Newtonian and power law flow for a range of viscosity and feed ratios at different Reynolds numbers using the finite element technique. Computations demonstrate that the more viscous fluid tends to push into the less viscous component. The dimensionless development length required for the interface to reach its final position is an increasing function of viscosity ratio and Reynolds number. Surface tension has a stabilizing effect which is more pronounced for the converging channel downstream geometry. Furthermore, a comparison of short- and longwave stability analyses with the present numerical results reveals that the normal stresses generated by the converging channel downstream play a major role in interfacial stability of multiphase flows. Moreover, the present results reveal some important trends that can be expected in coextrusion operations.

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