Dynamic characteristics of droplet impact on rotating blades

This study explores the breakup modes and splashing dynamics of droplets impacting a rotating blade using high-speed shadow imaging combined with advanced image processing techniques. Experiments cover a broad range of rotational Weber numbers (2 × 103 to 2 × 105), enabling systematic analysis of droplet deformation, secondary droplet generation, and splashing morphology. Three spreading modes—upper-surface spreading, lower-surface spreading, and droplet cutting—are identified, along with two primary post-impact outcomes: rebound and breakup. The transition between these regimes is rationalized using the tangential impact number, which provides a dimensionless criterion for predicting rebound–breakup behavior. The aerodynamic effect of rotor downwash on the liquid film and droplets is estimated, with estimated Froude numbers (Fr ≫ 1) indicating negligible gravitational influence. Empirical correlations reveal strong nonlinear influences of the dimensionless collision time and tangential Weber number on spreading diameter and secondary droplet size, with scaling laws established for both regimes. Secondary droplet fragmentation follows a gamma distribution, and splashing morphology depends strongly on collision mode, ranging from symmetric radial ejection to fan-shaped spreading. These findings deepen the physical understanding of droplet–rotor interactions under high-inertia conditions and provide a quantitative framework for modeling and optimizing processes involving icing, erosion, and gas–liquid two-phase flows in rotorcraft and rotating machinery.