NUMERICAL STUDY OF VISCOPLASTIC FLOW IN A T-BIFURCATION: IDENTIFICATION OF STAGNANT REGIONS

Abstract Identification of stagnant regions of viscoplastic fluid flows in production lines and equipment is of paramount importance owing to potential material degradation and process contamination. The present work introduces an assessment strategy to identify, classify and quantify unyielded regions with the objective of optimizing the flow conditions with the purpose of minimizing stagnant regions. Flow of Carbopol® 980 in a T-bifurcation channel is adopted to illustrate the procedure. The rheological behavior of Carbopol® 980 was simulated using the Herschel-Bulkley viscoplastic model regularized by Papanastasiou’s exponential approach. The analysis shows that three distinct types of stagnant unyielded regions take place in the bifurcation channel depending upon the Reynolds condition. Furthermore, the rheological characteristics of the fluid indicate the existence of an ideal Reynolds condition which allows the smallest flow stagnant area at the bifurcation zone.

摘要 由于存在材料降解与工艺污染的潜在风险，识别生产线及设备中粘塑性流体流动的滞流区域至关重要。本研究提出一种评估策略，用于识别、分类并量化未屈服区域，旨在优化流动条件以最小化滞流区域规模。本研究采用T型分叉通道内的卡波姆（Carbopol®）980流体流动来演示该方法流程。本研究采用帕帕纳斯塔西乌指数正则化的赫谢尔-布尔克利（Herschel-Bulkley）粘塑性模型，对卡波姆980的流变行为进行数值模拟。分析结果表明，根据雷诺条件的不同，分叉通道内会出现三种截然不同的滞流未屈服区域类型。此外，流体的流变特性表明存在一组理想雷诺条件，可使分叉区域内的流动滞流面积达到最小。