摘要
运用二维激光多普勒测速仪,测定了运动气泡近界面的动力学特性,其中包括时均特性及湍流场结构.实验表明,尾涡区的时均流速呈非均匀分布,湍流场由双结构组成,即由完全随机的湍流涡及规律性的相干涡构成,这种双结构现象在尾涡的中心及边缘部又有所变化,其相关函数、谱密度函数及统计尺度亦随不同的部位而变化.泡前区受尾涡区周期性Karman涡脱落的影响,呈现相同频率的周期波动.这种特性存在于切向及法向速度中.
It is commonly recognized that micro behavior near the interface have considerable significance in the understanding of the mass transfer mechanism in two phase processes. In this work, two dimensional laser doppler anemometer technique has been employed to investigate the hydrodynamics and turbulent structure near the interface of a moving bubble. In our experiment, a bubble was fixed in a specially designed gas-liquid channel with the liquid phase flowing down from top to bottom so as to keep the bubble stationary.
It was discovered that in the center of the bubble wake near interface the tangential velocity exhibited large scale coherent structure caused by Karman vortex shedding and the normal velocity showed more stochastic behavior than the tangential. In the edge of the bubble wake, both tangential and normal velocity consisted of the large scale coherent and stochastic vortex. The time averaged normal velocity near rear interface diminished from center to edge of the wake, but the tangential one showed only a little change. The integral scales near rear interface changed appreciably, having maxima in the center of wake and minima in the edge with micro scales remained unchanged. Near the frontal interface, both the tangential and the
normal velocities presented regular vibration with the same frequency as the Karman vortex shedding in the bubble wake, while the integral and the micro scales exhibited the same behavior as in the rear interface.
The present study on the turbulent behaviors near interface may provide some basic information for understanding the mass transfer mechanism and efficiency in two phase processes.
出处
《化工学报》
EI
CAS
CSCD
北大核心
1992年第5期570-576,共7页
CIESC Journal
基金
国家自然科学基金项目
关键词
气泡
速度场
激光多普勒
界面
测量
bubble, velocity field, laser doppler anemometer
