Digital holography is applied to the visualization of viscoelastic flows due to the presence of polymers with high molecular weight in the studied liquids.
The experiment is carried out on a filament stretching device of the CABER (Capillary Breakup Extensional Rheometer) type. It is a geometry where a viscoelastic filament is stretched between two plates in a controlled manner. For certain concentrations of polymers, we observe the appearance of small drops (or beads) moving on the filament. The figure below shows the reconstructed hologram of a zone of the filament.
This optical device is very simple: the flow is illuminated by a laser beam and the holographic figure produced by the filament is directly recorded on a camera without an imaging lens (lensless imaging system). By reconstructing the hologram plane by plane, it is possible to focus on each image. It thus becomes possible to characterize finely:
without prior knowledge of the 3D position of the objects.
More details on the following movie:
M. Kozulic,M. Mirzaei, G. Godard, D. Lebrun, O. Crumeyrolle, MC. Renoult. 3D monitoring of a pearling instability. APS Division of Fluid Dynamics, 2019, Portland, United States. ⟨hal-02418339⟩ V0034, 72th Annual Meeting of the APS Division of Fluid Dynamics (November 23, 2019 — November 26, 2019). DOI: https://doi.org/10.1103/APS.DFD.2019.GFM.V0034