厚覆冰导线升力突变机理及数值模拟研究

针对新月形厚覆冰导线的升力系数在风攻角15°附近存在突变的问题,分别采用基于k-ωSST湍流模型的雷诺时均法和大涡模拟(LES)的数值方法对新月形厚覆冰导线在风攻角10°~20°范围进行了模拟。通过对比两种数值方法计算得到的覆冰导线气动力系数、流场结构和表面风压,发现LES方法能够更好地捕捉新月形覆冰导线表面的小尺度涡结构,得到的覆冰导线气动力参数计算结果与风洞试验数据高度吻合;而k-ωSST湍流模型难以模拟壁面上小尺度涡,捕捉不到升力系数的突变。根据覆冰导线不同壁面区域的压力分布,发现上侧壁面处的涡结构影响整体流场,并在下侧壁面曲率、来流夹角和壁面切线方向共同作用下导致升力系数突变。LES的气动力参数模拟结果可为覆冰导线防舞提供参考。

CFD simulation on thick crescent-shape iced conductor and mechanism of sudden change in lift coefficients

To understand the sudden change in the lift coefficient of a thick crescent-shape iced conductor at a 15°angle of attack,numerical simulations were carried out using both the Reynolds Average Navier-Stokes(RANS)equations with the k-ωSST turbulence model and the large eddy simulation(LES),in a range of angles of attack from 10°to 20°,and the aerodynamic characteristics and flow fields were obtained.By comparing the aerodynamic coefficients,flow structures and surface wind pressure distributions computed from the two numerical methods,it is found that the LES performs better in modelling the small-scale vortex structures near the surface of the crescent-shape iced conductor.In addition,the LES results have higher accuracy and are highly consistent with the wind tunnel test data.However,the k-ωSST turbulence model fails to capture small-scale vortices on the surface as well as the sudden change in the lift coefficient.According to the pressure distribution on different surface areas of the iced conductor,it is found that the vortex structure on the upper wall affects the overall flow field,whereas the combined action of the lower wall surface curvature,the incoming flow angle and the wall tangent direction lead to the sudden change in the lift coefficient.The aerodynamic forces predicted from the LES results can provide a reference for anti-galloping measures of iced conductors.