ONERA 3-DIMENSIONAL ICING MODEL

A three-dimensional icing model has been developed at ONERA to calcula te ice accretion shapes for aerodynamic components that can not be pre dicted using conventional two-dimensional codes. It is described, emph asizing the original parts with respect to the two-dimensional existin g models. The model includes Euler inviscid flow calculation. Droplet trajectories are calculated in a three-dimensional grid. The remesh on the Leading edge is adapted to follow aerodynamics singularities. The boundary layer is calculated using a mixing length formulation to mod el the wall roughness influence on convective heat transfer. Runback p aths are integrated. The heat balance is calculated in a grid created along the runback paths. The domain of validity of the three-dimension al icing code is described; compared with the two-dimensional model th is domain is wider, especially for high speeds. The three-dimensional model is shown to simulate well a uniform ice deposit on a three-dimen sional rotor blade tip. Then, a comparison of the three- and two-dimen sional codes on an infinite swept wing shows that the corrected two-di mensional code predicts the catch efficiency but not the ice shape. Fi nally, it is shown that the continuum flux hypothesis prevents the thr ee-dimensional model from simulating correctly the ''lobster tail'' ic e shape (nonuniform ice deposit).