基于PIV技术的单圆孔脉冲射流流场特征

对稳态射流及脉冲射流冲击靶板时的流场特性结构进行了探索和分析。采用高频粒子图像测速技术,在射流管口到冲击靶板间距为6倍管径的条件下,对稳态射流进口雷诺数为6 000的稳态射流及脉冲频率为20 Hz的脉冲射流进行了实验测量,得到了射流核心区、壁面射流区及滞止区内的速度分布。研究发现:①由于射流剪切作用的影响,脉冲射流核心区的最大轴向脉动速度为稳态射流的3倍。②滞止区内,由于射流的剪切作用和壁面的滞止作用,导致了脉冲射流轴向速度梯度最大为稳态射流的2倍,同时,滞止区内的最大脉动速度是稳态射流脉动速度的3倍。③脉冲射流对壁面的卷吸以及旋涡的产生和传播过程,破坏了壁面射流区稳定的速度边界层。相比稳态射流,脉冲射流的流场增加了湍流相干结构的含能并产生周期性的大尺度卷吸涡。

Flow field characteristics of single round hole pulsed jet based on PIV technology

The flow field characteristic structure of steady and pulsed jet impinging on the target plate was investigated. High frequency particle image velocity measurement technology was used to measure a steady jet and a pulsed jet with a frequency of 20 Hz. Besides, the distance between the jet nozzle and the target plate was 6 times the diameter of the nozzle, and the steady jet inlet Reynolds number was 6 000 for both steady and pulsed jet flows. The experiment obtained velocity distribution of the core jet zone, the wall jet zone, and the stagnation zone. The results show that: (1) due to the shear action of the jet, maximum axial fluctuation velocity in the core jet zone of the pulsed jet was nearly three times that of the steady jet. (2) In the stagnation zone, the maximum gradient of the axial velocity of the pulsed jet was approximately twice that of the steady jet, which resulted from the shear action of the jet and the stagnation action of the wall. Furthermore, the maximum fluctuation velocity in the stagnation zone was nearly three times that of the steady jet. (3) The entrainment of the pulsed jet and the propagation of the vortex led to the destruction of the velocity boundary layer in the wall jet region. Compared with the steady jet, the flow field of the pulsed jet increased the energy of the turbulent coherent structure and generated periodic large-scale vortex.