Flow and mixing analysis of a thixotropic fluid in a barrier-emb e dde d partitioned pipe mixer (BPPM): A numerical study

Abstract

Flow and mixing characteristics of a thixotropic fluid in a static mixer were numerically investigated in this study. We selected a barrier-embedded partitioned pipe mixer (BPPM) as the model static mixer, whose geometric design parameters are fixed for the simplicity of the analysis. The Moore structurekinetics model was employed to describe a thixotropic fluid, whose flow and mixing characteristics were systematically analyzed for cases with specific combinations of three dimensionless numbers: the apparent Reynolds number ( R e a ), thixotropy number ( Th ), and destruction parameter ( k d ). The structure parameter ( lambda) showed a highly reduced value near the barrier tip, where the highest shear deformation occurred. The average lambda dramatically decreased with Th as the fluid thixotropy becomes significant. k d is related to the standard deviation of lambda because it controls the magnitude of the material derivative of lambda. As R e a increased, more complex flow and mixing behaviors were observed, especially at a higher Th . From the qualitative and quantitative analyses of the Poincare section and flux-weighted intensity of segregation ( I d ), the mixing performance was seen to improve with Th in the counter-rotational BPPM, while a more complex trend of the degree of mixing was found in the co-rotational BPPM. This study provides a comprehensive understanding of thixotropic fluid mixing with an emphasis on the complex relationship between the flow characteristics and mixing performance. (c) 2021 Elsevier Ltd. All rights reserved.