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Issue 8, 2020
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X-ray particle tracking velocimetry in liquid foam flow

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In this work, we introduce a novel approach to measure the flow velocity of liquid foam by tracking custom-tailored 3D-printed tracers in X-ray radiography. In contrast to optical observations of foam flow in flat cells, the measurement depth equals 100 mm in the X-ray beam direction. Light-weight tracers of millimetric size and tetrapod-inspired shape are additively manufactured from stainless steel powder by selective laser melting. Matching with the foam structure and bubble size, these tracers follow the foam flow. An X-ray beam passes through the radiotransparent foam channel and is detected by an X-ray image intensifier. The X-ray transmission images show the two-dimensional projections of the radiopaque tracers. Utilizing particle tracking velocimetry algorithms, the tracer trajectories are measured with both high spatial (0.2 mm) and temporal (25 fps) resolution. Fine and coarse liquid foam flow of different velocities are studied in a partly curved channel with rectangular cross section. The simultaneous time-resolved measurements of the tracers’ translational motion and their intrinsic rotation reveal both the local velocity and vorticity of the foam flow. In the semi-circular curved channel section, the rigid-body-like flow pattern is investigated. Moreover, a relaxation of the foam structure in the transition zone between straight and curved section is observed.

Graphical abstract: X-ray particle tracking velocimetry in liquid foam flow

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Article information

28 Oct 2019
16 Jan 2020
First published
04 Feb 2020

Soft Matter, 2020,16, 2093-2103
Article type

X-ray particle tracking velocimetry in liquid foam flow

T. Lappan, A. Franz, H. Schwab, U. Kühn, S. Eckert, K. Eckert and S. Heitkam, Soft Matter, 2020, 16, 2093
DOI: 10.1039/C9SM02140J

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