高速冲击射流中的涡结构和冲击单音

Vortex structure and impinging tone in high-speed impinging jet

冲击射流广泛应用于短距、垂直起降飞行器(STOVL)等航空航天领域,然而却伴随着流场与噪声等诸多方面的问题,需要深入研究其流动特性和噪声机理,特别是二者之间的关联。采用PIV(粒子图像测速)技术对高速冲击射流的流场结构和涡结构进行深入研究,探讨流场与声场的相关性,发现冲击单音的存在与否及强弱与涡结构的存在与否及强弱大小相对应,且冲击单音随压比、冲击距离、喷嘴唇厚等参数变化的规律也与涡结构与这些因素的变化规律相一致,因此涡结构和冲击单音具有很强的相关性;并且螺旋模态与对称模态对应不同频率的冲击单音,在同一工况下可能存在两种流动模态共存的情况,此时冲击单音也具有多频率特性。因此抑制大尺度涡结构的发展是降低冲击单音的重要环节,可为冲击射流的降噪研究奠定涡声理论基础。

Impinging jets are widely existed in many engineering fields, such as a short takeoff and vertical landing （STOVL） aircraft, as well as air nozzle etc. The flow characteristics and noise produced in the impingement process have been paid more attentions. In this paper, vortex structures and flow patterns are studied by PIV （Particle Image Velocimetry） technology. The relationship between flow field and acoustic filed is obtained. It found that the existence and intensity of the vortex structure varied with different pressure ratio, impinging distance and nozzle lip thickness were similar to the impinging tone did. There are different impinging tone frequencies corresponding to helical and synunetric flow pattern. So it is an effective way to reduce impinging tone by controlling large-scale vortex structure.