Predicting the Collection Efficiency on a Generic Rotor Blade with a Three-Dimensional Eulerian Particle Solver

Ice accretion on helicopter rotor blades when flying through supercooled droplet clouds can severely affect aerodynamic properties and pose a significant threat to flight safety. In the design phase, manufacturers commonly use 2D or quasi-3D simulations to predict potential ice accretion, which are more economical than fully 3D approaches. However, these methods frequently encounter accuracy issues when predicting the precise amount of ice accretion because the 3D flow field significantly influences droplet trajectories and, as a result, impingement and accreted mass. For this study the Eulerian particle solver of the icing software DICEPS was upgraded from 2D to 3D using second-order schemes, ensuring numerical stability on unstructured mesh configurations. Validation of the 3D modifications was performed by comparing numerical results of the collection efficiency on a sphere with experimental data. Droplet trajectory calculations were then conducted on a NACA0012 rotor in hover flight using a rotating frame of reference, including centrifugal and Coriolis forces. Results indicated an expected increase in collection efficiency with increasing radial position and droplet Stokes number. In addition, the resolved 3D blade tip vortex of the preceding rotor blade resulted in a significant variance in collection efficiency for certain rotor radii. These findings highlight the importance of using full 3D simulations for accurate prediction of ice accretion on helicopter rotor blades and can aid in the development of improved design strategies for safe helicopter operations under icing conditions.