螺旋桨空化崩溃性能图谱的多相流模拟

Multiphase flow simulation and propeller cavitation breakdown performance maps

为了提高螺旋桨空化性能多相流模拟的精度,采用改进数值模型对NSRDC4381螺旋桨的片空化形态和空化崩溃性能图谱进行了模拟与校验.数值模型由混合密度中显示包含非凝结性气核(NCG)质量分数和体积分数的混合物多相流模型,考虑湍流脉动影响的相变临界压力、NCG质量分数取7.8×10-4、NCG体积分数取1.0×10-6、气泡平均初始半径取1.5μm的改进Sauer空化模型,以及剪切应力输运(SST)湍流模型组成.结果表明:预报空化崩溃性能图谱与实验值符合很好;非设计进速系数下模拟空化形态与采用Sauer空化模型的结果一致,较实验值略偏小;中度和重度空化下,推力和力矩系数的预报精度明显高于采用Kunz空化模型的结果,严重空化时精度提升约16%;即使在高负载且严重空化的非设计工况下,预报推力和力矩系数误差分别为4.95%和2.28%,也在工程可控范围内,证明了所采用数值模型的有效性.该模型可进一步用于螺旋桨空化初生的数值判定.

In order to improve the multiphase viscous simulation precision of propeller cavitating per- formances, NSRDC4381 propellerr s sheet cavitation pattern and cavitating breakdown performance maps were conducted, using the mixture multiphase model which contained both of the non-condensa-ble gas （NCG） mass and volume fractions effects in the mixture density, the phase-changing threshold pressure accounting for the effect of turbulence, the improved Sauer cavitation model which got the NCG mass and volume fraction were7.8×10^-1and 1.0×10^-6 respectively and the bubble initial radi-us was 1.5 μm, and the modified shear stress transport turbulence model. The results show that predicted cavitation breakdown performance maps are fit very well with the experiment data. Under undesign condition, the simulated cavity pattern is under-estimate but similar to that in reference usingSauer cavitation model. Under moderated and severe cavitation conditions, thrust and torque coefficient prediction are obvious better than the reference using Kunz cavitation model, especially up to 16% for the severe condition. Even under the highly-loaded and severe cavitation condition, predictionerrors of thrust and torque coefficients are 4.95% and 2.28% respectively, which gives a qualification of the numerical models and can be used to predict the cavitation inception in the next step.