Confined Swirling Flows of Aqueous Surfactant Solutions Due to a Rotating Disc in a Cylindrical Casing

In this study, confined swirling flows of an aqueous surfactant solution due to a rotating disc in a cylindrical casing were investigated using a sectional flow visualization technique and a two-component laser Doppler velocimetry (LDV) system. The concentrations of aqueous surfactant solutions (C₁₄TASal) are 0.4, 0.8, and 1.2 wt%. Rheological properties such as a shear viscosity and a first normal stress difference of the surfactant solution were measured with a rheometer. The patterns of the secondary flow were classified using the Reynolds and elastic numbers. We revealed that the projection formed near the center of the rotating disc was moving up and down at a constant frequency for C₁₄TASal 0.8 and 1.2 wt%, which has not been reported as far as we know. The effects of the Reynolds number, elastic number, and aspect ratio on the velocity profiles were clarified. It was also found that the region of rigid body rotation existed at the higher Reynolds number tested for C₁₄TASal 0.4 wt%.