桨叶剖面空泡形态发展特性研究

  目的  水下翼型空泡数下降到某个临界值后，翼型前缘位置的压强会降低而发生空化。在模型试验研究中，模型尺度翼型难以满足实尺度翼型的雷诺数，使得空化起始对应的空化数发生变化。  方法  为此，以航速为24 kn的标准KCS船采用的NACA 0012型船舵作为参照，基于STAR-CCM+软件，运用SST k-ω湍流模型和Schnerr-Sauer (S-S)空化模型对翼型空泡特性进行数值模拟。针对不同缩尺比模型，通过改变不同攻角时的翼型环境压强来计算翼型表面流场和空泡分布，得到空化起始对应的空化数，分析尺度效应对临界空化数的影响机理。  结果  结果表明，随着模型尺度的缩小，相应攻角下的翼型临界空化数也有一定程度的减小，说明雷诺数的差异会加剧尺度效应。  结论  因此，为防止尺度效应对起始空泡数的影响，模型试验中不宜选用较小尺度的翼型。

Research on characteristics of cavitation shape development on blade sections

  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.