PIV is the modern standard for measuring velocity fields in turbulent and complex flows. In PIV, patches of particles are tracked as they cross flow sections illuminated by lasers.

PLIF profilometry is a standard approach.  A two-dimensional profile of an interface is identified with a laser plane and camera imaging from the air side.

Time-resolved PIV for interface shear

Main publications

MA ANDRE and PM BARDET.  Free surface over a horizontal shear layer: vorticity generation and air entrainment mechanisms. Journal of Fluid Mechanics. 813:1007-1044, https://doi.org/10.1017/jfm.2016.822 (2017).

MA ANDRE and PM BARDET.  Viscous stress distribution over a wavy gas–liquid interface. International Journal of Multiphase Flow. 88:1-10, https://doi.org/10.1016/j.ijmultiphaseflow.2016.07.004 (2017).

Fine pattern generation for profilometry

In an iteration of the PLIF profilometry, the laser sheet is changed to a structured illumination sheet.  Ray tracing enables to reconstruct the interface in 3D in front of the structured laser sheet.

Main publications

E FLOROU, C FORT, MA ANDRE, M HABUKAWA, and PM BARDET. Surface reconstruction in three‑dimensional space using structured illumination. Experiments in Fluids. 64:70, https://doi.org/10.1007/s00348-023-03608-9 (2023).

C FORT, MA ANDRE, H PAZHAND, and PM BARDET. Talbot-effect structured illumination: pattern generation and application to long-distance μ-MTV. Experiments in Fluids. 61(2):1-21, https://doi.org/10.1007/s00348-019-2870-7 (2020).