Analysis of cavitation number and scale effect of hydrofoil cavitation initiation

  Objective  When the cavitation number drops to a certain critical value, the pressure at the leading edge of an underwater hydrofoil will decrease and cavitation will occur. In model test studies, it is difficult for a scale model hydrofoil to meet the Reynolds number of a real scale hydrofoil, so the critical cavitation number during cavitation initiation will be changed.

  Methods  To this end, with reference to the NACA 0012 rudder used in the standard KCS ship with a speed of 24 knots, the hydrofoil cavitation characteristics are numerically simulated in the paper using the SST k-ω turbulence model and Schnerr-Sauer (S-S) cavitation model based on STAR-CCM+ software. According to different scale models, the surface flow field and cavitation distribution of the hydrofoil are calculated by changing the environmental pressure of the hydrofoil at different attack angles. In this way, the critical cavitation number corresponding to cavitation initiation is obtained, and the influence mechanism of the scale effect on the critical cavitation number is analyzed.

  Results  Through the analysis of the calculation results, it is concluded that with the decrease in scale, the size of the critical cavitation number at the corresponding attack angle of the hydrofoil will decrease, indicating that the scale effect caused by the difference in the Reynolds number is intensified.

  Conclusion  Therefore, in model tests, in order to prevent the influence of the scale effect on the initial cavitation number, a hydrofoil of a smaller scale should not be selected.