Asymptotic analysis of viscoelastic effects on dynamic contact angles at high shear rates

When a non-Newtonian liquid, such as a polymer solution, displaces air on a flat solid surface, the contact angle between the liquid-air and liquid-solid interfaces exhibits dynamic behavior that depends on the surface velocity and the fluid's rheological properties. Recent experimental data indicate that normal stress approaches a constant value at very high shear rates. In this study, we analyze the high-shear-rate behavior of the system by solving the equations of motion to obtain film profiles and dynamic contact angles, incorporating both shear thinning and normal stress effects. The rheological model is extended to reflect the asymptotic behavior of normal stresses, enabling accurate prediction of contact angles at high shear rates for the first time. Comparison with experimental measurements further allows estimation of the constant normal stress values in these systems.