Measurement of foam flow using Ultrasound Doppler Velocimetry + Froth dynamics by Neutron Imaging

The flowing behavior of liquid foam and froth is only scarcely investigated. One reason for that is, that no adequate measurement technique exists. Also, industrial flotation applications could be improved by monitoring the froth flow in the process.

In this work, the Ultrasound Doppler Velocimetry has been used to measure the velocity distribution inside liquid foam. To that end, an array of ultrasound transducers sends pulses into the foam and receiving the echoes. Sound pulses are reflected at moving particles and air-liquid interfaces. The echoes reveal the longitudinal velocity distribution on the beam axis. Multiplexing of the array allows for 2D-1C measurement.

Comparing with optical measurement it is demonstrated, that the velocity uncertainty at 2.5 Hz frame rate is below 15 percent and the spatial resolution better than 10 mm. These parameters allow for on-line monitoring of industrial processes as well as scientific investigation of three-dimensional froth and foam flows.