Ultrasonic measurements of the velocity distribution inside foam

The flowing behavior of liquid foam and froth is not yet well investigated. One reason for that is, that adequate measurement techniques are scarcely available. Also, industrial foam applications could be improved by monitoring the foam flow in the process.

In this work, the ultrasound Doppler velocimetry is used to measure the velocity distribution inside liquid foam. (Nauber et al. “Ultrasonic measurements of the bulk flow field in foams.”, Physical Review E, vol. 97 (1), pp 013113, 2018). To that end, an array of five ultrasound transducers is positioned inside a foam channel. One transducer sends pulses into the foam and the others receive the echoes. Sound pulses are reflected at moving particles and air-liquid interfaces. The echoes reveal the longitudinal velocity distribution along the beam axis. Multiplexing of the array allows for 2D-1C measurement.