Faculty of Electrical and Computer Engineering, Laboratory for Measurement and Sensor System Technique, TU Dresden, 01069 Dresden, Germany.
Institute of Fluid Dynamics, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstrasse 400, 01328 Dresden, Germany.
Phys Rev E. 2018 Jan;97(1-1):013113. doi: 10.1103/PhysRevE.97.013113.
The flow field of moving foams is relevant for basic research and for the optimization of industrial processes such as froth flotation. However, no adequate measurement technique exists for the local velocity distribution inside the foam bulk. We have investigated the ultrasound Doppler velocimetry (UDV), providing the first two-dimensional, non-invasive velocity measurement technique with an adequate spatial (10mm) and temporal resolution (2.5Hz) that is applicable to medium scale foam flows. The measurement object is dry aqueous foam flowing upward in a rectangular channel. An array of ultrasound transducers is mounted within the channel, sending pulses along the main flow axis, and receiving echoes from the foam bulk. This results in a temporally and spatially resolved, planar velocity field up to a measurement depth of 200mm, which is approximately one order of magnitude larger than those of optical techniques. A comparison with optical reference measurements of the surface velocity of the foam allows to validate the UDV results. At 2.5Hz frame rate an uncertainty below 15 percent and an axial spatial resolution better than 10mm is found. Therefore, UDV is a suitable tool for monitoring of industrial processes as well as the scientific investigation of three-dimensional foam flows on medium scales.
动泡沫的流场与基础研究和工业过程的优化有关，例如泡沫浮选。然而，目前尚不存在适用于泡沫体内部局部速度分布的适当测量技术。我们研究了超声多普勒测速法（UDV），这是首次提供具有适当空间（10mm）和时间分辨率（2.5Hz）的二维、非侵入式速度测量技术，适用于中规模泡沫流动。测量对象是在矩形通道中向上流动的干燥水基泡沫。一组超声换能器安装在通道内，沿着主流轴发送脉冲，并从泡沫体接收回波。这导致了一个时间和空间分辨率高达 200mm 的平面速度场，比光学技术的测量范围大一个数量级。与泡沫表面速度的光学参考测量进行比较，验证了 UDV 的结果。在 2.5Hz 的帧率下，发现不确定性低于 15%，轴向空间分辨率优于 10mm。因此，UDV 是监测工业过程以及在中规模上研究三维泡沫流动的理想工具。
