Taylor-vortex flow in shear-thinning fluids

Area of Science:

• Fluid dynamics
• Rheology
• Non-Newtonian fluid mechanics

Background:

• Taylor-Couette flow is a fundamental configuration for studying fluid dynamics.
• Understanding non-Newtonian fluid behavior, particularly shear-thinning, is crucial in various industrial applications.
• Viscosity variations significantly influence flow patterns.

Purpose of the Study:

• To investigate the influence of viscosity stratification and nonlinear viscosity variation on shear-thinning fluid flow in the Taylor-vortex regime.
• To provide a first-principles understanding of these effects on flow structure.
• To analyze nonlinear effects using high-order amplitude expansion and numerical computations.

Main Methods:

• Weakly nonlinear analysis using high-order amplitude expansion.
• Numerical computation employing the Carreau model for shear-thinning behavior.
• Systematic variation of rheological parameters in a wide gap configuration (η=0.4).

Main Results:

• Increased shear-thinning leads to vortex squeezing towards the inner wall and axial shifting towards outflow boundaries.
• Outflow regions strengthen, while inflow zones with low vorticity expand.
• The pseudo-Nusselt number decreases, indicating reduced torque compared to laminar flow.
• Higher harmonics become more significant and grow faster with increasing Reynolds number.

Conclusions:

• Shear-thinning significantly modifies the flow structure in Taylor-Couette systems.
• The observed changes in vortex dynamics and energy distribution have implications for transport phenomena.
• The study provides a detailed description of the viscosity field modification under shear-thinning conditions.