亚格子模型对三维扭曲水翼空化现象的影响

Influence of subgrid-scale models on cavitation phenomenon around a 3D twisted hydrofoil

[目的]旨在探究三维扭曲水翼空化数值模拟中网格密度及亚格子模型的适应性问题。[方法]为此,使用大涡模拟(LES)方法和Schnerr-Sauer(S-S)空化模型对Delft Twist11N三维扭曲水翼的非定常空化流场进行数值模拟,重点研究3套不同密度的网格和WMLES,SL,WALE这3种亚格子模型对Delft Twist11N水翼空化演变过程、空化脱落频率及时均升阻力系数等的影响。[结果]结果表明:适当的网格加密形式既能够捕捉到较多的细小空泡脱落、马蹄形云空泡的初生与溃灭等非定常空化演变现象,又能够获得具有较高精度的空泡脱落频率、时均升阻力系数和时均压力分布。相较于WMLES和SL亚格子模型,WALE亚格子模型较好地捕捉到了片空泡及云空泡的演变,在预报空泡脱落频率、时均升阻力系数及压力系数方面精度较优。[结论]因此,推荐采用基于WALE亚格子模型的LES方法进行非定常云状空化的数值模拟。

[Objective]This paper aims to explore the suitability of mesh density and subgrid-scale model for the numerical simulation of three-dimensional twisted hydrofoil. [Methods]The large eddy simulation(LES) method and Schnerr-Sauer(S-S) cavitation model are used to simulate the unsteady cavitation flow of a Delft Twist11N three-dimensional twisted hydrofoil. Three sets of grid with different density and three types of different subgrid-scale models are mainly studied to identify the effects on the Twist11N hydrofoil cavitation evolution process, cavitation shedding frequency and time-averaged lift and drag coefficients.[Results]The results show that appropriate grid refinement can not only capture more unsteady cavitation evolution phenomena such as the shedding of smaller cavities and the inception and collapse of horse-shoe-shaped cloud cavities, but also obtain more exact cavity shedding frequency, time-averaged lift and drag coefficients, and time-averaged pressure distribution. Among the three subgrid-scale models, compared to the algebraic wallmodeled LES model(WMLES) and Smagorinsky-Lilly(SL) model, the wall-adapting local eddy-viscosity(WALE) model better captures the evolution of sheet and cloud cavitation, and has better accuracy in predicting the frequency of cavity shedding,time-averaged lift, drag and pressure coefficients.[Conclusion]It is recommended to adopt the LES method with the WALE subgrid-scale model for the numerical simulation of unsteady cloud cavitation.