片状液体

任何粒度测试设备测得的非球形颗粒的粒径都是等效粒径。棒状和片状颗粒是两种比较典型的非球形颗粒，本文研究这两种颗粒在激光粒度仪中的等效粒径。论文四－－立论和计算模型，是本文的第一部分，主要介绍激光粒度测量系统，棒状和片状颗粒光散射问题的近似处理方法，以及相应的数学推导。

In this work the influence of the internal flow field on the liquid film was investigated. A strategy for reliablePIV measurements inside of nozzle channels with a height of only a few hundred micrometers and at flowvelocities of several m/s has been developed. These PIV measurements provided 2 dimensional snapshots of thevelocity field inside the nozzle as well as velocity- and fluctuation-profiles across the channel. The developmentof the channel flow could be observed along the channel length at laminar and partly turbulent flow conditions.Disturbances were introduced to the flow field by inserting a wire into the channel flow. PIV measurementsshowed the resulting change of the nozzle flow (in the wake of the wire and without wire, respectively). Theresulting effects on the free liquid film were observed using back-lit photographs and perpendicular lightsectionsthrough the film surface. In the case of the undisturbed nozzle, velocity fluctuations occurred mainly inthe boundary layer and the fluctuations in main streamwise direction were dominant. The free liquid film of thisnozzle was smooth at the exit and only at higher Re numbers the growth of surface waves could be observedfurther downstream. The nozzle with inserted wire showed a high level of velocity fluctuation in the center of theflow. Here, the fluctuations normal to the walls were of the same magnitude as the fluctuations in streamwisedirection. The liquid film of this nozzle was roughened directly below the nozzle exit, even at low Re numbers.The high level fluctuations normal to the wall are assumed to play the dominant role in this process. Thesemeasurements demonstrate the influence of the internal flow field on the liquid sheet. The results of the presentwork agree well with recent experiments of Heukelbach and Tropea [1] and supplement the existingexperimental data which for example can be used as input or validation of numerical simulations.

任何粒度测试设备测得的非球形颗粒的粒径都是等效粒径。棒状和片状颗粒是两种比较典型的非球形颗粒，本文研究这两种颗粒在激光粒度仪中的等效粒径。论文五是本文的第二部分－－有关结论，该部分结合激光粒度仪的光能数据分析方法，用模拟计算的方法推算出各种径厚比的片状颗粒和各种长径比的棒状颗粒的等效粒径（分布），从中分析、总结出结论。