PREDICTION OF ICE ACCRETION - COMPARISON BETWEEN THE 2D AND 3D CODES

A 2D and a 3D icing model have been developed. Both start with inviscid flow calculation followed by calculation of droplet trajectories. They derive the heat transfer coefficient from the thermal boundary layer calculation on a rough wall. In the 3D case, the runback paths are calculated from the wall streamlines. The heat and mass balance gives the accretion rate, from which, we deduce the ice shape. The catch efficiency coefficient, the heat transfer coefficient and the ice shapes are compared with experimental data. The 3D code is compared with the 2D on an infinite swept wing. We see that the corrected 2D code can predict the local catch efficiency but not the ice shape. Then the Messinger approach is discussed and the 3D ''lobster tail'' effect is explained through the shadow effect and a heat transfer gradient mechanism. A qualitative balistic model enables us to simulate this type of ice shape growth.