Complex flow around a bubble rising in a non-Newtonian fluid

Area of Science:

• Fluid dynamics
• Non-Newtonian fluid mechanics
• Computational physics

Background:

• Understanding bubble dynamics in non-Newtonian fluids is crucial for various industrial processes.
• Complex rheological behaviors, like shear thinning, significantly alter fluid flow patterns.
• Experimental and numerical methods are essential for characterizing these intricate phenomena.

Purpose of the Study:

• To investigate the complex flow features of a rising bubble in a shear-thinning non-Newtonian fluid.
• To develop and validate a computational model for simulating such two-phase flows.
• To compare numerical predictions with experimental observations.

Main Methods:

• Experimental investigation using particle image velocimetry and birefringence modulation.
• Numerical modeling coupling a free-energy-based lattice Boltzmann scheme with a sixth-order Maxwell model.
• Simulation of a Newtonian low viscosity drop to represent a rising bubble.

Main Results:

• Observed complex flow features, including a negative wake behind the rising bubble.
• Successfully predicted the bubble's characteristic teardrop shape.
• Obtained detailed stress field distributions around the bubble.
• Numerical results showed satisfactory agreement with experimental data.

Conclusions:

• The coupled lattice Boltzmann and Maxwell model effectively captures complex bubble dynamics in non-Newtonian fluids.
• The study provides valuable insights into the interplay between fluid rheology and bubble deformation.
• Validated numerical approach can be used for further studies in complex fluid flows.