摘要
采用大涡模拟方法对垂直于来流的圆盘(直径为40 mm,厚度为8 mm)后尾迹中的湍流特性进行了研究.流动雷诺数分别是1×10^4、1×10^5和2.5×10^5.发现当Re>1×10^4时流场的平均速度、雷诺应力和阻力系数等的分布受雷诺数影响较小,圆盘绕流产生的阻力主要取决于圆盘前后的压力差.通过分析流场的频谱特性,研究高雷诺数条件下圆盘尾迹中的湍流结构及不稳定机制,发现3个无量纲特征频率St≈0.028,St≈0.138~0.146和St≈1.437,分别对应于近尾迹中的回流区沿轴向脉动、驻定涡旋脱落和Kelvin-Helmholtz不稳定这3种不稳定性机制.
Large eddy simulations(LES)were performed to study the turbulent characteristics in the wake of a circular disk normal to the free air stream(the diameter of the disk is 40 mm,thickness is 8 mm).The Reynolds numbers are 1×10^4,1×10^5and 2.5×10^5 respectively.It was found that when Re>1×10^4,the distributions of mean velocity and Reynolds stress as well as drag coefficient vary little with Re.Drag coefficient is mainly contributed by the pressure difference between the front and rear of the disk.By means of power spectral density analysis,three most influential instability mechanisms are disclosed in the large scale structure of a disk’s near wake:a very low frequency(St≈0.028)corresponding to the recirculation bubble pulsation along an axis of symmetry;a natural frequency(St≈0.138~0.146)related to antisymmetric helical vortex shedding;and a high frequency(St≈1.437)associated with Kelvin-Helmholtz instability of the separated shear layer.
作者
谢忱
朱旻明
陈义良
XIE Chen;ZHU Minming;CHEN Yiliang(Department of Thermal Science and Energy Engineering, University of Science and Technology of China, Hefei 230027, China)
基金
国家自然科学基金(51576182)资助.
关键词
大涡模拟
圆盘
近尾迹
large eddy simulation
circular disk
near wake
