Objectives  In order to explore the hazards of propeller ventilation and to prevent that during the ship design stage, a study of CFD numerical simulation is carried out.

  Methods  The hydrodynamic performances of a propeller model with different immersion ratio and advance coefficients are calculated. The ventilation characteristics and the changes of propeller thrust and torque are analyzed. The changes of the non-constant loads of a blade are compared.

  Results  The results show that, for the immersion ratio h/D=1.0, the propeller has no ventilation, and its thrust and torque also have no significant change. For 0.6≤h/D<1.0, the propeller is affected by the free surface, and the thrust and torque have a certain reduction. For h/D<0.6, especially at lower advance coefficients, the propeller has a significant ventilation phenomenon and see a large decrease in the thrust and torque.

  Conclusions  The study shows that, it's possible the ventilation happens in small immersion ratios and at lower advance coefficients, accompanied with the thrust and torque descending rapidly and pulsing steeply.