Inertial lift on a particle in a straight microchannel of Newtonian, power-law and Carreau-Yasuda fluids: A simulation study toward optimized particle separation

Direct three-dimensional Numerical Simulations (DNS) are performed to calculate the inertial lift forces on a single particle in a straight rectangular microchannel of Newtonian fluid and xanthan gum solutions. The shear-thinning behavior of xanthan gum solutions is demonstrated experimentally and represented mathematically using the power-law and Carreau-Yasuda models. Similar to Newtonian fluids, our simulations delineate the dominant region of shear gradient and wall-induced lift forces for power-law and Carreau-Yasuda fluids. The variable viscosity of non-Newtonian fluids allows us to better control the particle motion which seems promising in the inertial focusing method. Owing to their different formulations, power-law and Carreau-Yasuda models result in inconsistent lift forces. This incompatibility appears to intensify at higher concentrations of xanthan gum (higher shear-thinning characteristics) solutions and stems from the fact that the power-law viscosity considerably diverges from the experimental and Carreau-Yasuda viscosity in both low and high shear-rate re-gions. The power-law model is more sensitive to the Re number compared to the Carreau-Yasuda model, espe-cially for high concentrations of xanthan gum solutions. Furthermore, the results indicate the presence of two equilibrium positions for both Newtonian fluid and xanthan gum solutions in the microchannel cross-section. By increasing the Re number, the Newtonian and Carreau-Yasuda fluids push the particle equilibrium positions toward the center of the microchannel while the power-law model pushes the equilibrium positions toward the microchannel wall. Furthermore, both power-law and Carreau-Yasuda models indicate the shift of equilibrium positions to the microchannel wall by increasing the shear-thinning characteristics.

Automated summary

Direct three-dimensional Numerical Simulations (DNS) are used to study the inertial lift forces on a single particle in a straight rectangular microchannel filled with Newtonian fluid and xanthan gum solutions. The shear-thinning behavior of xanthan gum solutions is experimentally demonstrated and mathematically represented using power-law and Carreau-Yasuda models. The simulations reveal the dominant region of shear gradient and wall-induced lift forces for both power-law and Carreau-Yasuda fluids, similar to Newtonian fluids. The variable viscosity of non-Newtonian fluids allows for better control of particle motion, particularly in the inertial focusing method.