Short note

The MST issue “Non-intrusive measuring techniques for free-surface flows” brings together papers that were originally presented at the 38th IAHR World Congress in Panama in a session promoted by the IAHR Experimental Methods and Instrumentation committee.

The selected papers propose advances on hardware and software to broaden the range of methods available to measure key flow variables and parameters in free-surface flows. In the case of velocimetry, this includes established methods such as PIV or PTV but also optical flow methods. Innovative proposals for visualization, optical access and image enhancement have been proposed to measure flow depths and transported quantities expressing sediment transport and solute concentrations. Laser-based methods have been used to reconstruct bed morphology while advances in photogrammetry and 3D scanning have allowed to reconstruct detailed geometries of channels and free-surface. 

By focusing on non-intrusive techniques, the selected papers for the issue are on the forefront of measuring techniques for free-surface flows. I hope this issue will be recognized as a significant contribution to field of measurement science providing methods that, ultimately, will improve our ability to gather empirical evidence and to advance knowledge on the physics of free-surface flows. 

Rui M,L. Ferreira

Chair of the Experimental Methods and Instrumentation of IAHR