arXiv subjects

Médéric Argentina

Publications and source records attributed to Médéric Argentina.

4 recordsLinked to original sources

arXiv2026

Quantifying the liquid flow between a soap film and a vertical meniscus

Fluid exchange between a soap film and its bounding menisci governs film drainage and stability, with direct implications for the lifetime of surface bubbles and liquid foams. Despite recent advances, a quantitative characterization of this coupling, associated with the phenomenon of marginal regeneration, remains incomplete. The volumetric flux per unit length of contact follows a well-established scaling law involving geometrical parameters such as the film height and the meniscus radius of curvature. However, the dimensionless prefactor of this relation - the flux coefficient - remains difficult to determine for vertical menisci because of the complex and intermittent flows occurring at the film-meniscus interface. Here, we quantify this flux into the meniscus generated by inserting a solid plate into a vertical soap film. We consider both vertical and inclined plates and further investigate the effects of plate inclination, height, and width. Focusing on the dynamics of the growth of the meniscus driven by liquid supplied by the film, we analyze both steady and transient regimes resulting from the interplay between capillary pressure, gravity, and liquid exchange. Combining experiments, numerical simulations, and theoretical modelling, we determine the flux coefficient using three independent methods and show that it remains constant over the range of parameters explored.

physics.flu-dyn↗

arXiv2025

Undulatory underwater swimming: Linking vortex dynamics, thrust, and wake structure with a biorobotic fish

Flapping-based propulsive systems rely on fluid-structure interactions to produce thrust. At intermediate and high Reynolds numbers, vortex formation and organization in the wake of such systems are crucial for the generation of a propulsive force. In this work, we experimentally investigate the wake produced by a tethered robotic fish immersed in a water tunnel. By systematically varying the amplitude and frequency of the fish tail as well as the free-stream speed, we are able to observe and characterize different vortex streets as a function of the Strouhal number. The produced wakes are three-dimensional and exhibit a classical V-shape, mainly with two oblique trains of vortex rings convecting outward. Using two-dimensional Particle Image Velocimetry (PIV) in the mid-span plane behind the fish and through extensive data processing of the velocity and vorticity fields, we demonstrate the strong couplings at place between vortex dynamics, thrust production and wake structure. We first measure the evolution of the vortex velocity with the Strouhal number, and model it using a momentum balance equation directly related to thrust production. We then focus on the wake structure, such as wake angle as well as vortex ring orientation, diameter and vorticity. The wake structure is modelled in a simple geometrical framework where the vortex ring velocity is composed of the free-stream speed and the ring self-advecting speed. This framework is tested and validated by our experimental measurements as well as literature data collapsing on master curves, highlighting a universal behavior dominated by the Strouhal number. This allows us to establish a comprehensive understanding of how the wake structure varies with this number and, thus, thrust production.

physics.flu-dyn↗

arXiv2024

Curvature-driven transport of thin Bingham fluid layers in airway bifurcations

The mucus on the bronchial wall forms a thin layer of non-Newtonian fluid. One of the roles of mucus is to protect the lungs by capturing inhaled pollutants. It is transported by mucocilliary clearance toward the tracheo-pharyngeal bifurcation, where it is eliminated. Due to the corrugation of its interface with air, the mucus layer is subject to surface tension forces that interact with its rheology. It is still not clear whether these forces can affect mucus displacement and, if they can, under what conditions and how this displacement can occur. In this work, we model the mucus as a thin Bingham fluid layer located on the wall of idealized, multi-scaled airway bifurcations. We analyze the resulting physical system using lubrication theory and 3D simulations. The theoretical analysis allows us to characterize the nonlinear behavior of the system and determine the geometric conditions under which the Bingham fluid can be moved by surface tension. 3D simulations are then used to quantify the effects in idealized airway bifurcations on a range of scales corresponding to those of bronchial bifurcations. Our results suggest that surface tension effects can displace overly thick mucus layers in airway bifurcations, a typical situation in obstructive lung pathologies (asthma, BPCO, cystic fobrosis, etc.). Moreover, our results indicate that this movement can disrupt mucociliary clearance and the homogeneity of the layer thickness, thus increasing the risk of lung infection.

physics.flu-dyn↗

arXiv2017

Dynamics of elastically strained islands in presence of an anisotropic surface energy

The equilibrium solutions and coarsening dynamics of strained semi-conductor islands are investigated analytically and numerically. We develop an analytical model to study the effect of surface energy anisotropy on the dynamics coarsening of islands. We propose a simple model to explain the effect of this anisotropy on the coarsening time. We find that the anisotropy slows down the coarsening. This effect is rationalised using a quasi-analytical description of the island profile.

cond-mat.soft↗