Gaële Perret

Dual-wavelength digital holography for 3D particle image velocimetry: experimental validation

A multi-exposure digital in-line hologram of a particle field is recorded by two successive pulses of different wavelengths. During the reconstruction step, each recording can be independently analyzed by selecting a given wavelength. This procedure enables avoiding the superimposition of particle images that may be close to each other.

Simultaneous 3D location and size measurement of bubbles and sand particles in a flow using interferometric particle imaging.

We present a system to characterize a triphasic flow in a 3D volume (air bubbles and solid irregular particles in water) using only one CCD sensor. A cylindrical interferometric out-of-focus imaging setup is used to determine simultaneously the 3D position and the size of bubbles and irregular sand particles in a flow. The 3D position of the particles is deduced from the ellipticity of their out-of-focus image. The size of bubbles is deduced from analysis of interference fringes. The characteristics of irregular sand particles are obtained from analysis of their speckle-like pattern. Experiments are confirmed by simulations.

3D-shape recognition and size measurement of irregular rough particles using multi-views interferometric out-of-focus imaging.

We realize simplified-tomography experiments on irregular rough particles using interferometric out-of-focus imaging. Using two angles of view, we determine the global 3D-shape, the dimensions, and the 3D-orientation of irregular rough particles whose morphologies belong to families such as sticks, plates, and crosses.

Dual Wavelength Digital Holography for 3D Particle Image Velocimetry: Application to Vortex Dynamics

The two wavelengths multi-exposure method is applied to study vortices generated by interaction between a swell and an immerged plate. However, in such flows, the range of velocities to be measured is large. We show that a well-chosen pulse sequence enables to achieve velocity measurements both in the core and in the periphery of the vortex.

Digital in-line Holography for Particle Diagnostics in Flows

Due to the simplicity of its optical configuration, in-line holography offers an attractive way to particle characterization. This configuration opens the way to onboard measurement systems. Several applications for flows studies are presented such as near-wall velocity measurements, bubbles and droplets sizing.