Surface wave spectrum in boxed free-surface turbulence*

In the present study free surface turbulence (FST) is explored in a canonical FST facility based on a non-intrusive optical diagnostic for reconstruction of liquid-gas interfaces in the 3D space and time with one single laser plane and camera. 

The 3D interfacial topography is acquired based on a robust ray tracing algorithm by imaging from the gas phase a 2D, vertical grid written directly in the liquid phase. The nature of the grid and its orientation allow to adapt the technique in various spatio-temporal scales, perform the profilometry simultaneously with velocimetry, simplify the experimental set up and extend the applicability of the refraction-based profilometers to both small and steep waves. The images can be processed both as individual and time resolved events; the latter case provides up to 30% more points in steep FS regions.

The FST facility design principles are similar to the ones in traditional “boxed turbulence” configurations; symmetrically placed agitators disrupt the flow in an open cylindrical chamber. FS-wall interactions are minimized with a passive wave breaker. Data from this facility, wave spectra and more details about the algorithm will be presented at the conference.