Effect of blowing out on NACA0012 airfoil surface in order to prevent of ice accretion was studied numerically. Holes with regular pattern were generated over the leading edge of airfoil. Velocity of air injection, diameter, pitch of holes, and symmetrical angle of two rows about of cord line and arrangement of holes, diamond, and rectangle were varied. Shear-stress transport k-ω model was chosen to simulate the turbulence closure model, which makes better prediction for the case of pressure gradient over airfoils. Protective layer of air injections caused to prevent water droplets from the impact and strike to the airfoil surface. Results indicated that the diameter has the most effect on lowering of the ice accretion. In addition, pitch of the holes has the second most important role for reduction of ice weight. Reduction of 89% in the ice accretion in the presence of blowing out was achieved.

In order to prevent the ice-accretion on the airfoil surface, an experimental study was conducted to investigate effect of injecting surrounding air from the surface into the main flow. For this purpose, holes were created at the leading edge of the airfoil. Five parameters of diameter, pitch, angle of position, holes arrangement, and velocity of the outlet flow from the holes were sought. Using principles of experimental design by two-level fractional factorial method, required tests were designed and determined. Conducting tests, the results indicated the injection method significantly reduces weight of ice accreted on the surface. The highest amount of ice mass reduction in experiments reached 85% of the ice mass accreted on the simple airfoil. The diameter and pitch of holes had greatest effect on reducing the mass of ice accreted on the surface, followed by the injection airflow rate and the angle of alignment. Therefore, the injection of air at lower temperature than freezing point is as effective for ice accretion and saves energy rather than using hot-air injection. Moreover, the injected air from holes created a protective layer around the surface, which enhanced the process.