【摘要】 为研究声激励对圆射流流场结构的控制作用,采用大涡模拟方法计算相锁定全局声激励下的圆射流(Re=2 020)流场.计算得出的未加激励时射流的优势频率与实验符合得很好.从多角度描述声激励对射流速度场和涡量场的影响,分析流场对声激励响应的频率选择特性.通过速度场的平均值、均方根值,概率密度函数,偏度,峰度,以及动量厚度的分布,显示声激励引起速度场和混合特性的改变.涡量和Q准则揭示流场拟序结构的演化,发现激励控制流场的主导涡结构是希尔球涡.研究表明,声激励是流场控制非常准确和有效的手段,当激励频率在优势频率附近时影响尤其明显,很小的能量输入便可以引起流场结构的显著改变.更多还原

【Abstract】 To investigate flow field structures of a round jet controlled by acoustic excitation,large eddy simulation(LES)was performed to calculate a round jet(Re=2 020)under phase-locked global acoustic excitation.The control effects on the velocity and vorticity fields were described in various perspectives,and the frequency selectivity of jet response was analyzed.The preferred model frequency of unmodulated jet agreed well with the experiments.The mean and root mean square(RMS)velocity,probability density functions(PDF),skewness,kurtosis and momentum thickness were used to explore the modification of velocity fluctuation and mixing properties. Vortical structures were illustrated by Q criterion and instantaneous vorticity.The key vortex structure in the modulated cases was identified as Hill’s sphere vortex.It is concluded that acoustic excitation can effectively control the flow field.Especially when the modulation frequency is near the preferred mode,a small amount of modulation energy input can cause significant change in flow structures.更多还原