Blockage and Three-Dimensional Effects in Wind-Tunnel Testing of Ice Accretion over Wings

Wind-tunnel testing of ice accretion over aircraft wings is simulated numerically to investigate the effects of tunnel blockage and of the wall–wing interference at the wall–model juncture. The open-source OpenFOAM software is used to compute the flowfield and the trajectories of water droplets. The PoliMIce ice-prediction software is applied to solve the multiphase flow around the body surface and to compute the thickness of the iced layer. Blockage effects are investigated for diverse operating conditions. Similar to dry testing, wind-tunnel blockage is found to produce a variation of the apparent angle of attack of the airfoil with respect to the freestream. However, different from dry testing, the blockage correction is found to be a function of time, due to the continuous modification of the airfoil shape in time resulting from ice accretion. The wall–wing interference results in the occurrence of a shadow region where water droplets do not impinge. In the rime-ice regime, the shadow region is therefore free of ice. In the glaze-ice regime, instead, the liquid film over the wing moves toward the endwall and ice is formed in the shadow region.