基于大涡模拟的波状前缘水翼空化抑制研究

为了降低空化造成的水动力性能损失，基于仿生学原理，参考座头鲸鳍肢剖面形状，将前缘波浪构型引入到水翼设计中，研究波状前缘水翼的非定常空化特性，并探究前缘参数改变对空化控制的效果和规律。选用NACA63₄-021水翼为基准模型，进行前缘参数化重构，设计出3种不同的波状水翼进行对比研究。采用大涡模拟（LES）方法对空化流场进行精细化数值模拟，针对基准水翼和不同波幅与波长参数下的波状水翼开展了空化周期、升阻力系数、压力脉动以及流向涡结构的对比分析。结果发现，波状水翼在抑制空化和降低压力脉动方面都取得了显著效果。其中，3种不同的波状水翼空化抑制率分别为15.7%、18.6%和27.9%，压力脉动幅值分别降低了55.3%、67.3%和74.6%。分析表明，波浪前缘的引入使得空化的分区效应更加凸显，空化从波谷处初生，增大波幅或减小波长都可以加强对空化的抑制效果，并可以提高升力系数以及显著降低水翼表面的压力脉动。前缘波浪构型还将诱发向下游发展的对转涡结构，不同前缘参数的波状水翼涡结构的演化是相似的，空泡发展与溃灭的整个过程对涡结构的发展也具有显著影响。

LES study of hydrofoil with wavy leading edge on cavitation suppression

In order to reduce the loss of hydrodynamic performance caused by cavitation, the wavy leading edge configuration is introduced into the hydrofoil design based on the bionics principle with reference to the profile shape of the flipper of a humpback whale. The unsteady cavitation characteristics of hydrofoil with wavy leading edge and the effect and law of cavitation control by changing leading edge parameters are studied. The NACA63₄-021 hydrofoil is selected as the reference model, the leading edge parametric reconstruction is carried out and three different corrugated hydrofoils are designed for comparative study. The large eddy simulation (LES) method is used to perform fine numerical simulation of cavitation flow field. The cavitation cycle, lift and drag coefficient, pressure fluctuation and vortex structure are compared for the baseline hydrofoil and the wavy hydrofoils under different wave amplitude and wavelength parameters. The results show that the wavy hydrofoils are effective in suppressing cavitation and reducing pressure fluctuation. The cavitation suppression rates of the three types of wavy hydrofoil are 15.7%, 18.6% and 27.9%, respectively. The pressure fluctuation amplitude is reduced by 55.3%, 67.3% and 74.6%, respectively. The analysis shows that the introduction of the wavy leading edge makes the compartmentalization effect of cavitation more prominent. Cavitation starts from the trough. The increase of amplitude or the decrease of wavelength can strengthen the control effect of cavitation. It also can improve the lift coefficient of the hydrofoil and significantly reduce the amplitude of pressure fluctuation on the surface of the hydrofoil. The wavy leading edge configuration also induces the counterrotating vortex structure that develops downstream. The evolution of the wavy hydrofoil vortex structure with different leading edge parameters is similar, and the whole process of cavitation development and collapse also has a significant impact on the development of the vortex structure.