Abstract

Yield stress fluids exhibit a distinctive flow behavior characterized by a persistent resistance to flow until an external force surpasses their yield stress threshold. In this thesis, we investigate mixing characteristics of yield stress fluids within a magnetic mixer. The experimental apparatus comprises an acrylic rectangular mixing vessel and a high-capacity magnetic stirrer. Rheological properties of Carbopol gels were meticulously analyzed, and the yield stress was precisely determined by fitting the data with the Herschel Bulkley model. The study utilizes both Particle Image Velocimetry (PIV) and Dye Visualization techniques to comprehensively characterize the flow dynamics. Stirring characteristics, including velocity norm and cavern formation, were systematically investigated in both transient and periodic states. Notably, our experimental findings unveil a distinct trend: as the ratio of inertial forces to viscous forces increases, there is a noticeable shift in the growth rate of velocity norm and cavern area, indicative of the increasing dominance of inertial forces. Moreover, our research employing the Dye Visualization method demonstrates that the cavern's shape remains consistent regardless of the position of the rod. In contrast, PIV results reveal that at lower ratios of inertial to viscous forces, the rod's position significantly influences the cavern's shape.