Scanning stereo-PLIF method for free surface measurements in large 3D domains

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 $L=100$ mm in a large two-dimensional domain ($y(x,z)=120\times 62$ mm${}^2$), with sufficient accuracy to determine small amplitude variations ($\eta \approx 0.2$ mm). The temporal resolution ($\Delta t=19$ ms) is only limited by the available scanning equipment ($f=1$ kHz rate). For other applications, this domain can be scaled as needed.