中文摘要：

采用大涡模拟（LES）方法模拟亚声速旋拧射流,着重考察温度效应对旋拧射流近场流动演化过程、湍流脉动空间发展和远场噪声的影响。线性稳定性分析表明,旋拧射流中提高射流中心温度会增加剪切层的扰动增长率;数值结果显示,加热会促进剪切层中大尺度结构的产生及相互作用,促使流动更快进入湍流状态,并缩短射流势核区的长度。在初始层流发展阶段,加热会提高中心线上的流向速度脉动峰值,但是对剪切层中的流向速度脉动峰值几乎没有影响;在湍流发展阶段,提高射流中心温度会提高流向速度脉动衰减率,并降低脉动幅值。此外,在非等温射流中,密度脉动幅值要远高于等温射流。在30°方位角附近,等温射流的总声压级幅值最高,冷射流的噪声幅值最低。方位角大于50°时,加热使总声压级降低,且随着方位角幅值的增大,降低越明显;而冷却则会提高总的声压级幅值。

英文摘要：

Large eddy simulation（LES）is performed for investigating temperature effects in subsonic swirling jets.The effects on the flow development and far-field noise are discussed in detail.The results of linear stability theory show that the growth rates of the shear layers are raised as the core temperature increases;the LES results show that heating promotes the interactions of large-scale structures,makes the flows develop into turbulence more quickly and shortens jet potential cores.At the laminar stage,heating raises the peak of axial velocities fluctuations in center lines;however,it has negligible influence on the peak values in shear layers.At the turbulent stage,as the core temperature increases,the levels of velocity fluctuations become lower and the decay rates become higher.Additionally,it is found that the density fluctuations in nonisothermal jets are much higher than those in isothermal jets.At polar angles near 30°,the overall sound pressure level of the hot jet is lower than that in the isothermal jet and higher than that in the cold jet.However,when polar angle is larger than 50°,heating reduces the sound pressure level and the reduction becomes much larger as polar angle increases.While,the sound pressure level increases slightly in the cold jet.