Measurement of the liquid fraction of foam by conductive wire-mesh sensor.

The liquid fraction (Φ) of foam is an important quantity in engineering process control and essentially to interpret foam rheology. Currently available methods are either complex laboratory-based techniques or cannot provide spatial resolution. Therefore, in this work in-situ measurement of the liquid fraction from foam's electrical conductivity [Feitosa, 2005] was studied by employing conductive wire-mesh sensor (WMS) [Prasser, 1998]. Two arrays of wires are placed inside the foam (figure 1) and at each crossing point the local liquid fraction is determined. This approach offers 2D measurement of liquid fraction distribution (figure 1) with very high frame rate. The measurements were validated by simultaneous measurement of liquid fraction by neutron radiography (NR) [Heitkam, 2018].
An systematic dependency between WMS readings and the true liquid fraction from NR is found (figure 1). However, WMS overestimates the liquid fraction systematically, which could be an effect of the liquid bridge formation between the wires.