Author(s): Yulia Akutina; Pengning Sun; Olivier Eiff
Linked Author(s): Olivier Eiff
Keywords: No Keywords
Abstract: In order to perform optical flow measurements around solid bodies, refractive-index matching (RIM) techniques are often employed: RI of a transparent object is matched with that of the working fluid. The solid becomes invisible" and a full optical access inside or behind the body is made possible free of distortions. In this work, we study the use of polymer THV since it has close RI to water allowing readily available sodium chloride (table salt) to be added to water in order to reach the necessary refractive index. For validation, an experimental flow set-up with a patch of THV tubes was prepared to allow the flow to be measured by two independent particle image velocimetry (PIV) systems. One camera views the flow at the edge of the patch through the patch while the other camera has a free optical path to the same measurement plane. Comparing the results from the two measurement systems gives an estimate of the measurement errors. A mathematical model of light refraction is employed to analyse the PIV errors and their dependence on the tubes' geometry. An optimal PIV box size to the tube thickness ratio is proposed.
Year: 2022