LEGI - UMR 5519

Title: Digital In-line holography in dispersed two-phase flows.

Contact : Nathanaël Machicoane

Abstract: 3D optical measurements meets a great success in Fluid mechanics, in particular with the recent progress of 3D Particle Tracking Velocimetry. Digital In-line holography is an elegant and performant alternative way to investigate two-phase flows in 3 dimensions, based on a rather simple optical set-up, composed of a low-power laser light source and a single camera.

3D information on a two-phase flow is deduced from a single hologram through a numerical reconstruction process. The reconstruction methods can be classified into two groups. The classical reconstruction methods are based on back-propagation of the light intensity. More advanced methods are based on an inverse problem approach. These methods require a priori knowledge on the diffracting objects (the particles in the flow), in the form of a parametric diffraction model or by introducing additional physical constraints. In return, these methods generally demonstrate a greater accuracy, for particle location along the optical axis and particle size in particular.

This seminar will provide an opportunity to recall the basics of holography, to evaluate the potential and the limitations of the technique for two-phase flow investigation with the help of some examples. Particular attention will be given to the tracking of evaporating droplets in turbulence, developed at LMFA in the last few years.