Predictive model for non-Newtonian droplet impact on moving solid surfaces

We have developed a refined predictive model for the spreading dynamics of non-Newtonian droplets impacting both stationary and moving surfaces. Using numerical simulations, the key physical mechanisms, including inertial spreading, shear-thinning effects, and capillary stabilization, were identified and integrated into the model. The model extends classical Newtonian frameworks by incorporating the time-dependent and shear-rate-dependent rheological properties of non-Newtonian fluids. The numerical framework employs the volume of fluid method combined with dynamic contact angle modeling to resolve interface dynamics and wetting behavior. Comparisons with experimental data for shear-thinning droplets (e.g., Parafilm-M at We = 24 and We = 94) demonstrated strong agreement within a 3% margin of error, confirming the model's accuracy. Notably, the model successfully captures anisotropic spreading induced by surface motion, a phenomenon neglected in prior studies. Notably, the model accurately captured anisotropic spreading induced by surface motion, a phenomenon neglected in existing frameworks. The results highlight the model's robustness in generalizing across trained and untrained conditions, emphasizing its applicability for industrial processes such as inkjet printing, spray coating, and pharmaceutical droplet deposition. This work establishes a comprehensive framework for understanding and predicting the complex dynamics of non-Newtonian droplet impacts.