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Home page > Séminaires > Séminaires 2022 > MSC Internal Seminar. October 17th 2022. 11:30. Camille Le Scao : "A front propagation model of leaf growth" and Guillaume Ricard "Transition from wave turbulence to acoustic-like shock wave regime".

MSC Internal Seminar. October 17th 2022. 11:30. Camille Le Scao : "A front propagation model of leaf growth" and Guillaume Ricard "Transition from wave turbulence to acoustic-like shock wave regime"

Sauf mention contraire, les séminaires et les soutenances se déroulent à 11h30 en salle 454A du bâtiment Condorcet.


Monday October 17th 11h30. Room 454. Two talks of 30 min, Camille Le Scao then Guillaume Ricard.

A front propagation model of leaf growth

Camille Le Scao

PhD under the supervision of Stéphane Douady and Julien Derr.

Leaves are photosynthetic organs with a diversity of shapes and complex vascular networks. During morphogenesis, two modes of growth are distinguished, peripheral and global. In order to explain the peripheral development, we propose a numerical model of growth by interface propagation describing the dynamics of the vein network as a function of the initial shape of the front and the spacing of the veins.In the case of a single lobe growth, we find an unstable central vein, whose position oscillates in the middle of the lobe. Its dynamics can be modeled by an iterated function whose geometry explains the instability. On the contrary in nature the central vein presents very stable oscillations. It is therefore necessary to modify the model and introduce a feedback loop. In a second model where the growth of the front is dependent on the position of the veins, we find two lobes by edge effect and an oscillation of the growth front, similar to an optical mode. This basic model can be modified to study the global growth.


Transition from wave turbulence to acoustic-like shock wave regime

Guillaume Ricard

PhD under the supervision of Eric Falcon.

Wave turbulence is a statistical state in which numerous random weakly nonlinear waves interact with each other. It leads to an energy cascade from large scales down to small scales driven by resonant interactions between waves. This state is first evidenced experimentally in a one dimensional canal for dispersive gravity-capillary waves on the surface of mercury. Then by using a ferrofluid and a high external magnetic field, we managed to experimentally create a transition from dispersive wave turbulence to a nondispersive regime involving coherent structures which are found to be shock waves. These structures are characterized by a significant steepening with a discontinuity and correspond to singularities in their second order derivative. Because of the discontinuities, shock waves then transfer energy at every scales instantly and become thus the main process to cascade energy over scales.


Contact : Équipe séminaires / Seminar team - Published on / Publié le 13 octobre 2022


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