中文摘要：

采用大涡模拟方法研究了圆柱在Re=4.1×10 4下的绕流场,预测了圆柱表面的脉动压力平均值和RMS值,得到了与试验报道接近的阻力系数平均值和升力脉动RMS值,以及涡脱St数,表明了大涡模拟的有效性.揭示了圆柱涡脱的空间不同步和涡脱频率随时间的变化特征,以及涡脱能量的有限频率带宽分布;分析了圆柱表面θ=90°和θ=270°点脉动压力时程的统计特性,表明脉动压力的能量均集中在圆柱的漩涡脱落频率上.提出了基于θ=90°和θ=270°点脉动压力时程的互相关系数和RMS值,合理估算圆柱截面脉动升力RMS值的公式;基于圆柱表面脉动压力时程的相干性分析,揭示了圆柱升力和阻力产生的流动机理.

英文摘要：

Based on the large eddy simulations （LES） for flow around circular cylinder at Re=4.1× 104,the mean and root mean square （RMS） of fluctuating pressure on circular cylinder are presented,with the mean drag coefficient,fluctuating lift coefficient and particularly the vortex-shedding Strouhal number being in good agreement with available reports.It is found that the vortex shedding is not in phases along the spanwise direction,and also the shedding frequency feature may change with flow time,while the vortex-shedding energy is concentrated to a limited frequency band.Statistics show that the fluctuating pressure time series at θ=90° and θ=270° on the opposite side of the circular share the same features,and the pressure fluctuating energy is also concentrated to the vortex-shedding frequency.An equation,based on the correlation coefficients and RMS of the fluctuating pressure time series at θ=90° and θ=270°,is provided to estimate the sectional fluctuating lift on the cylinder.The flow mechanism involved in drag and lift on cylinder is discussed according to the coherence function of the fluctuating pressure between the upper and lower cylinder surface.