Abstract:

Two-dimensional high-speed particle image velocimetry was used to study horizontal-confronted twogroup-layered impinging turbulent flow fields. Flow structures of two sets of nozzles were analyzed under conditions of different Re, nozzle diameter, upper and lower radial jets. The velocity field was decomposed by POD to extract large scale energy-carrying structure. The results show that low-order intrinsic mode features a large-scale vortex structure with obvious vortex structures in flow field and energy of transient flow field mainly concentrates in the first-order mode. Flow characteristics of whole flow field is easily described such that modal reconstruction of pulsating field could accurately reestablish vortex structures in the flow field. Under condition of L=3d, asymmetric flow field energy was higher than that of symmetric flow filed, low order modal energy was increased with increasing nozzle Re, but was first increased then decreased with the increase of nozzle diameter. Under condition of 10 mm diameter, first order mode energy was the highest and vorticity was the maximum.

Key words: double stratified impinging stream, two-dimensional high-speed particle image velocimetry, intrinsic mode, vortex structure, energy

摘要：

利用二维高速粒子图像测速技术研究双组分层水平对置撞击流湍流场，考察了双组喷嘴在不同Re、不同直径及上下径向射流不同工况下的流动结构，对速度场进行POD分解，提取流场中含能大尺度结构。结果表明，低阶本征模态拥有大尺度涡旋结构，流场涡旋结构明显，瞬时流场能量主要集中在一阶模态，易于描述整个流场的流动特征，脉动场的模态重构可以准确还原流场中的涡结构。L=3d工况下，不对称流场能量高于对称流场；低阶模态能量随喷嘴Re的增大而增大，而随喷嘴直径增大呈先递增后递减的趋势，直径d=10 mm的工况下所对应的一阶模态能量最高，涡强最大。

关键词: 双组分层撞击流, 二维高速粒子图像测速技术, 本征模态, 涡旋结构, 能量