高雷诺数下管内垂直降膜瞬时厚度空间分布及波动特性

Spatial Distribution and Wave Characteristics of Falling Liquid Film in Scrubbing-Cooling Tube under High Reynolds Numbers

研究了高雷诺数条件下(Rel=2.04×104)洗涤冷却管内下降液膜的空间分布及波动特性。采用超声波多普勒测速仪对不同轴向和周向位置的下降液膜瞬时厚度进行了无接触测量。结果表明:在高雷诺数条件下,管内液膜处于高湍动状态,液膜表面波动剧烈,平均参数无法准确描述液膜空间分布及波动特性。随着轴向和周向距离的增加,膜表面波动幅度及大波频率减少,小波频率增加。轴向上,液膜瞬时厚度概论密度分布函数(PDF)曲线波峰高度随轴向距离增加而增高;周向上,PDF曲线呈单峰-双峰-单峰分布。

Spatial distribution and wave characteristics of falling liquid film in scrubbing-cooling tube under Reynolds number of2.04×10^4were investigated.The instantaneous thickness of the falling film at different axial and circumferential directions was measured non-intrusively by Ultrasonic Doppler Velocimetry.The results show that the liquid film in the tube is under extreme turbulent state and the wave fluctuates violently at high Reynolds numbers.Therefore,the spatial distribution and wave characteristics cannot precisely predicted by average parameters.Moreover,the amplitude and large-wave frequency decrease and the small-wave frequency increases with the increase of axial and circumferential distances.The wave height of Probability Density Function of instantaneous thickness increases with the increase of axial distance,and the curve shows unimodal-doublet-unimodal distribution in the circumferential direction.