湍流边界层内不同粒径颗粒行为的PIV实验研究

PIV experimental study on behavior of particle with different size in turbulent boundary layer

为探究不同粒径颗粒在湍流边界层中的运动规律,采用粒子图像测速技术(PIV)对颗粒在平板湍流边界层内运动行为进行研究,分析同一来流速度条件下速度剖面、湍流度、雷诺应力统计量。运用新象限分裂法和空间相位平均法提取"喷射"和"扫掠"事件的脉动速度、雷诺应力二维空间拓扑形态。发现:颗粒速度剖面无太大差别,大颗粒湍流度和雷诺应力比小颗粒大,颗粒流向湍流度均大于法向湍流度;大颗粒脉动速度及喷射数目大于小颗粒,小颗粒喷射数目小于扫掠事件,说明大颗粒与周围流体动量交换更强烈,能量输运更强,在化工生产及污水处理方面更具前景。

To explore the motion rule of particles with different size in turbulent boundary layer,Particle Image Velocimetry(PIV)is applied to study the behavior of particle in the turbulent boundary layer.The velocity profile,turbulence and Reynolds stress statistics under the same flow velocity are analyzed.The new quadrant method and phase-average method are used to extract the two-dimensional spatial topology of the fluctuation velocity and the Reynolds stress for the“ejection”and“sweep”events.The results show that there is not much difference in particle velocity profile.The turbulence and Reynolds stress of large particles are larger than those of small particle,and the particle flow turbulence is greater than normal turbulence.The fluctuation velocity and number of ejection events of large particle are larger than small particles′,and the number of ejection events for small particles is smaller than the sweeping events,which indicates that the momentum exchange between large particles and the surrounding fluid is stronger,and the energy transport is stronger.Large particles is more promising in chemical production and sewage treatment.