自激振荡型气动喷嘴的实验及数值模拟研究

Experimental and Numerical Simulation of Self-excited Oscillation Pneumatic Nozzle

设计并加工了一种自激振荡型气动喷嘴,通过开展实验研究,探讨了该喷嘴的无量纲结构参数长径比、腔径比以及运行参数对自激振荡效果的影响。运用延迟分离涡模拟方法,对自激振荡型喷嘴的内外流场进行了非定常数值模拟研究,揭示了自激振荡脉冲射流的产生机理。结果表明:内置特定空腔结构的气动喷嘴可以实现出口压力的高频振荡,实验工况范围的最优参数组合为长径比、腔径比,振荡频率达104数量级,振荡的标准差离散系数的范围为0.02~0.36。非定常计算结果表明,喷嘴空腔内锐边结构对高速射流剪切,造成不稳定涡系周期性产生、迁移和湮灭是喷嘴内外流场压力振荡产生的根源。

A self-excited oscillation pneumatic nozzle was designed and manufactured.And the effects of dimensionless structure parameters,such as length-diameter ratio,cavity-diameter ratio,and operation parameters on the self-excited oscillation are discussed through experiments.Based on Delayed Detached-Eddy Simulation(DDES),unsteady numerical simulation was carried out,and the mechanism of self-excited oscillation pulsed jet was revealed.The results indicate that the high frequency oscillation of outlet pressure can be achieved by the pneumatic nozzle with a specific cavity structure.The optimum dimensionless structure parameter ratio in the experimental range is obtained,which length-diameter ratio is,cavity-diameter ratio is,oscillation frequency is 104 orders of magnitude,and standard deviation dispersion coefficient is 0.02~0.36.The unsteady calculation results show that the high-speed jet is sheared by the sharp edge structure in the nozzle cavity,causing periodic generation,migration and annihilation of unstable vortices,which is the source of oscillation of pressure inside and outside the nozzle.