Helical wires fitted on the surface of circular cylinders can suppress the Karman vortex shedding and reduce the vortex-induced vibration,but the exact control mechanism has not been clarified yet.Large eddy simulation method is adopted to investigate the flow field around a circular cylinder with three tripping wires at a subcritical Reynolds number (Re=4 × 104) in this paper.The effects of the wires on the aerodynamics of the circular cylinder are investigated.The relationships between the flow patterns,the pressure field and aerodynamic forces are discussed as well.It is revealed that the three wires have significant effects on the aerodynamics of the circular cylinder,with the maximum mean drag coefficient increasing about 32％ as comparison to a plain circular cylinder,and the maximum mean drag and lift coefficients increasing 50％ and 37％ compared to a cylinder with one single tripping wire.The Strouhal number decreases monotonically with the increase of the wire location angle β.Due to the impact of the tripping wires,the airflow tends to separate at the tripping wire position,which results in a wider width of the wake and a larger mean drag coefficient.When one tripping wire is located atβ=50°,the shear layer separated from the tripping wire will reattach to the surface of the cylinder to form one single separation bubble,which induces a local strong negative pressure on the surface and a high non zero mean lift on the circular cylinder.%在亚临界雷诺数下(Re=4×104),采用大涡模拟方法对带三根绊线圆柱绕流场进行了数值模拟,研究了圆柱表面风压分布、平均气动力和Strouhal数(St)随绊线位置角(β)的变化规律,分析了带绊线圆柱的流场流态与气动性能之间的相关性,探讨了分离泡对圆柱气动性能的影响机制.研究表明:三根绊线会对圆柱的气动性能造成很大影响,其最大平均阻力系数较带单根绊线圆柱与光圆柱分别提升了 32％及50％左右,最大平均升力系数则比单绊线圆柱高37％;带三绊线圆柱的St数低于光圆柱,并会随着β的增加单调递减;受绊线的影响,气流往往会在绊线位置提前分离,从而导致带三根绊线圆柱的尾流宽度较光圆柱更宽,并导致圆柱的阻力系数增大;绊线在β=50°附近时,在绊线分离的剪切层会再附到圆柱表面,形成单侧分离泡,这会导致圆柱表面出现局部强负压,并受到平均升力的作用.
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