LAUSR

In this work, we extend a planar laser-induced fluorescence method for free surface measurements to a three-dimensional domain using a stereo-camera system, a scanning light sheet, and a modified self-calibration procedure. The stereo-camera set-up enables a versatile measurement domain with self-calibration, improved accuracy, and redundancy (e.g., possibility to overcome occlusions). Fluid properties are not significantly altered by the fluorescent dye, which results in a non-intrusive measurement technique. The technique is validated by determining the free surface of a hydraulic flow over an obstacle and circular waves generated after droplet impact. Free surface waves can be accurately determined over a height of $$L=100$$ L = 100  mm in a large two-dimensional domain ( $$y(x,z) = 120\times 62$$ y ( x , z ) = 120 × 62  mm $$^2$$ 2 ), with sufficient accuracy to determine small amplitude variations ( $$\eta \approx 0.2$$ η ≈ 0.2  mm). The temporal resolution ( $${\varDelta }t = 19$$ Δ t = 19  ms) is only limited by the available scanning equipment ( $$f = 1$$ f = 1  kHz rate). For other applications, this domain can be scaled as needed. Graphic abstract