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   Home > Instabilities, Waves and Turbulence > Measurement by FS-SS of a liquid interface

Measurement by Free-Surface Synthetic Schlieren of the topography of a liquid interface

F. Moisy, M. Rabaud

We have developed an optical method for the measurement of the instantaneous topography of the interface between two transparent fluids, named Free-Surface Synthetic Schlieren, or FS-SS (Moisy et al, 2009). This method is based on the analysis of the refracted image of a random dot pattern visualized through the interface. The apparent displacement field between the refracted image and a reference image obtained when the surface is flat is determined using a Digital Image Correlation algorithm. A numerical integration of this displacement field, based on a least square inversion of the gradient operator, is used for the reconstruction of the instantaneous surface height, allowing for an excellent spatial resolution with a low computational cost. The main limitation of the method, namely the ray crossing (caustics) due to strong curvature and/or large surface-pattern distance, is discussed.

A tutorial for implementing a FS-SS system under Windows is available here.

A plane wave generated by an oscillating plate.

Wake pattern generated by the translation of a small obstacle (comparison experiment / numerics).

Movie of the circular wave created by the impact of a drop (Acquisition rate 100 Hz).

Movie of the spreading of a silicon oil drop on a transparent substrate.

3D reconstruction of a cross-wave, generated by the vertical oscillation of a fully immersed wavemaker. What are cross-waves?.


  • Surface deformations and wave generation by wind blowing over a viscous liquid
    A. Paquier, F. Moisy, and M. Rabaud, Phys. Fluids 27, 122103 (2015)
    [Abstract | PDF]
  • Crosswaves induced by the vertical oscillation of a fully immersed vertical plate
    F. Moisy, G.-J. Michon, M. Rabaud, E. Sultan, Phys. Fluids 24, 022110 (2012).
    [Abstract | PDF | movies]
  • Estimation des corrections non-linéaires dans la méthode FS-SS de mesure optique de la surface d’un liquide transparent
    M. Rabaud, F. Moisy, 20ème Congrès Français de Mécanique, 29 août - 2 septembre 2011, Besançon.
  • Unpredictable tunneling of a classical wave-particle association
    A. Eddi, E. Fort, F. Moisy, Y. Couder, Phys. Rev. Lett. 102, 240401 (2009).
  • A Synthetic Schlieren method for the measurement of the topography of a liquid interface
    F. Moisy, M. Rabaud, K. Salsac, Exp. in Fluids 46 (6), 1021-1036 (2009).
  • Measurement by Digital Image Correlation of the topography of a liquid interface
    F. Moisy, M. Rabaud, E. Pinsolle, ISFV13 - 13th International Symposium on Flow Visualization, and FLUVISU12 - 12th French Congress on Visualization in Fluid Mechanics, Paper #326, July 1-4, 2008, Nice (2008).
  • Optical measurement of ship waves by Digital Image Correlation
    M. Rabaud, F. Moisy, International Conference on Innovation in High Performance Sailing Yachts, 29-30 May 2008, Lorient, France, ISBN 978-1-905040-46-9e, pages 23-25 (2008).
  • Mesure de la déformation d’une surface libre par analyse du déplacement apparent d’un motif aléatoire de points
    M. Rabaud, F. Moisy and J. Rolland, Congrès Français de Mécanique (2007).

Last modification: April 28 2016, 01:23:05.