Numerical Study on the Motion Characteristics of Bubble Chains in Shear-thinning Liquids Based on the Euler-Lagrange Method

Research on the motion behavior of bubble chains in non-Newtonian fluids is of great significance for understanding the gas-liquid two-phase flow laws in practical engineering. In this paper, the Euler-Lagrange method is extended to the analysis of gas/shear-thinning liquid two-phase flow by introducing the power-law model. Considering no direct inter-bubble contact in a bubble chain, the mesh size constraint of the Particle Centroid Method (PCM) is relaxed to capture more flow details around the bubbles, and the results indicate that satisfactory computational accuracy can still be achieved when the mesh size is decreased to 1.6 times the bubble diameter. On this basis, the effects of flow index, bubble diameter and release period on bubble rise velocity and trajectory deviation in bubble chains are explored, with underlying mechanical mechanisms elaborated. Relative to Newtonian fluids, shear-thinning fluids generate higher velocity gradients around chain bubbles, inducing obvious bubble deviation dominated by strong Saffman force. Such deviation is closely related to the bubble position in the wake region of the leading bubble. For bubbles staying in the upper part of the region or outside the wake, their lateral deviation is governed by the balance between Saffman force and transverse viscous drag force; in contrast, for bubbles inside the middle and lower wake region, the deviation is mainly controlled by asymmetric vortex structures in the ambient flow field.