Non-intrusive measurement of complex free surfaces using Laser Induced Fluorescence and stereo imaging

A quasi three-dimensional stereo-camera measurement technique has been devised that is able to measure liquid free surface profiles, by scanning a light sheet. The technique will be applied to study the variability of impact pressure observed during wave impact in a newly developed experimental set-up. The set-up imposes severe optical (single window) and accessibility (autoclave) constraints. The devised measurement technique is required to measure liquid free surface profiles over a domain of (X,Y,Z) = (100, 100,100) mm domain with an accuracy of 1 mm. The performance of the devised measurement technique is evaluated using a convential side-view measurement (Buckley et al 2017) in the water tunnel of the Laboratory for Aero- and Hydrodynamics at the Delft University of Technology. A free surface profile is generated by flow over a bump geometry (Gui et al 2014), which provides a repeatable and increasingly complex free surface profile. The free surface profile is determined for three different cases over a domain of (X,Y,Z) = (170, 100, 62) mm with an averaged systematic error of 2.7 ± 1.2 mm. The observed error is systematic and implies that the edge detection procedure is not robust enough. In future work the systems measurement frequency and edge detection procedure will be improved.