Publications

2025

• Free surface topography of capillary flows using spatiotemporal phase shifting profilometry
  
  • de Miramon Hélie
  • Sarlin Wladimir
  • Huerre Axel
  • Cobelli Pablo
  • Séon Thomas
  • Josserand Christophe
  , 2025. We present a novel experimental technique to characterize the free surface of capillary flows adapted from the Spatio-Temporal Phase Shifting Profilometry (ST-PSP) method introduced by Ri et al. (Journal of Optics, 2019) for solid bodies. The present study is focused on various regimes of capillary flows over inclined surfaces, including drops, rivulets, meanders, and braided films. A calibration process is carried out using a solid wedge to determine the optical distances required for the phase-to-height relationship. The optimal dye concentration necessary for accurately reconstructing the free surface of a dyed water flow is explored. The ST-PSP method is then applied to profile different liquid flows and objects, achieving large signal-to-noise ratios across all experiments. Notably, the analysis of a sessile droplet shows a promising correlation between the ST-PSP results and side-view visualizations, as evidenced by the accurate recovery of its apparent contact angle. Furthermore, free surface reconstructions of rivulet flows exhibit good agreement with the theoretical predictions of Duffy and Moffatt (The Chemical Engineering Journal and the Biochemical Engineering Journal, 1995). These results suggest that the ST-PSP method is highly effective for obtaining accurate height maps of capillary flows and objects, making it a valuable tool for validating theoretical models in the future. (10.1007/s00348-025-04006-z)
  DOI : 10.1007/s00348-025-04006-z
• Incoherent Diffraction Imaging with a Pseudo-Thermal Light Source
  
  • Claveria Pablo San Miguel
  • Antunes Sesbastião
  • Biesterfeld Peer
  • Fernandes Matilde
  • Garcia Matilde
  • Nunes Matilde
  • Fernandez Lucas Ansia
  • Williams Gareth
  • Froehlich Sven
  • Theidel David
  • Mosel Philip
  • Fsaifes Ihsan
  • Trabattoni Andrea
  • Piccardo Marco
  • Chanteloup Jean-Christophe
  • Kovacev Milutin
  • Merdji Hamed
  • Fajardo Marta
  Optica Open, 2025. Incoherent Diffraction Imaging - IDI - is a diffraction-based imaging technique that has been recently proposed to exploit the partial coherence of incoherently scattered light to retrieve structural information from the scattering centers. Similar to the stellar intensity interferometry of Hanbury Brown and Twiss, the signal builds up on the second-order spatial correlations of the emitted light. The complex spatial distribution of the target is thereby encoded in the spatial intensity fluctuations of the scattered light. The first experimental realisations of this imaging technique have been realised using the fluorescence excited by an ultra-short X-ray pulse at Free Electron Laser (FEL) facilities. Here, we propose an alternative set-up based on a table-top Pseudo-Thermal Light Source. This set-up allows us to explore IDI under a wide range of physically relevant conditions as well as to benchmark numerical and analytical models currently used to determine the imaging capabilities of this technique. (10.48550/arXiv.2501.05417)
  DOI : 10.48550/arXiv.2501.05417
• Steady-state plasma model of an iodine-fueled Hall thruster
  
  • Chabert Pascal
  • Bourdon Anne
  • Esteves Benjamin
  • Lafleur Trevor
  Journal of Applied Physics, American Institute of Physics, 2025, 138 (4), pp.043303. A time-independent, one-dimensional plasma model is proposed and used to investigate the characteristics and performance of iodine-fueled Hall thrusters. The model accounts for radial plasma-wall losses and includes major iodine collisional reaction processes such as molecular dissociation. Thruster performance is found to be comparable to that obtained with xenon, although iodine allows extension of the operating range to lower mass flow rates and discharge voltages. The model predicts an appreciable fraction of molecular ions (I2+) within the thruster plume that depends on the discharge voltage and propellant mass flow rate and that contributes significantly to the thrust. In contrast to xenon, electron impact dissociation of iodine leads to the unique formation of two distinct ionization zones within the thruster: a region closer to the anode associated with the ionization of molecular iodine and a downstream region associated with the ionization of atomic iodine. (10.1063/5.0263183)
  DOI : 10.1063/5.0263183
• Modeling polycyclic aromatic hydrocarbons (PAH) and liquid organic hydrogen carriers (LOHC) with the SAFT-γ Mie group-contribution equation of state
  
  • Velásquez Sarmiento Edgar
  • Paricaud Patrice
  , 2025.
• Bridging multifluid and drift-diffusion models for bounded plasmas
  
  • Gangemi G M
  • Alvarez Laguna Alejandro
  • Massot M.
  • Hillewaert K.
  • Magin T.
  Physics of Plasmas, American Institute of Physics, 2025, 32 (2), pp.023502. Fluid models represent a valid alternative to kinetic approaches in simulating low-temperature discharges: a well-designed strategy must be able to combine the ability to predict a smooth transition from the quasineutral bulk to the sheath, where a space charge is built at a reasonable computational cost. These approaches belong to two families: multifluid models, where momenta of each species are modeled separately, and drift-diffusion models, where the dynamics of particles is dependent only on the gradient of particle concentration and on the electric force. It is shown that an equivalence between the two models exists and that it corresponds to a threshold Knudsen number, in the order of the square root of the electron-to-ion mass ratio; for an argon isothermal discharge, this value is given by a neutral background pressure Pn≳1000 Pa. This equivalence allows us to derive two analytical formulas for a priori estimation of the sheath width: the first one does not need any additional hypothesis but relies only on the natural transition from the quasineutral bulk to the sheath; the second approach improves the prediction by imposing a threshold value for the charge separation. The new analytical expressions provide better estimations of the floating sheath dimension in collisions-dominated regimes when tested against two models from the literature. (10.1063/5.0240640)
  DOI : 10.1063/5.0240640
• Refining the modeling strategy for anomalous electron transport in fluid simulations of Hall thrusters via insights from PIC simulations
  
  • Petronio Federico
  • Alvarez Laguna Alejandro
  • Guillon Martin Jacques
  • Bourdon Anne
  • Chabert Pascal
  Physics of Plasmas, American Institute of Physics, 2025, 32 (7), pp.073513. Modeling anomalous transport in fluid simulations is a fundamental challenge for developing efficient and robust fluid simulation tools for Hall thrusters. This paper investigates optimal strategies for modeling anomalous transport in such simulations. Using the particle-in-cell (PIC) benchmark (BM) setup of Charoy et al., we demonstrate that various terms in the electron momentum equation can be readily identified. In particular, we show that the assumption of expressing the rate of change of the electron momentum due to instability as proportional to the momentum itself does not hold under these simulation conditions. Subsequently, we present two fluid simulations that replicate the conditions of the PIC BM setup. The first employs the conventional empirical anomalous collision frequency approach. While this model provides generally satisfactory results, it fails to capture specific plasma characteristics. The second fluid model adopts a data-driven approach to represent the anomalous force terms in the momentum equation. This approach furnishes significantly improved results, suggesting that although the anomalous collisionality framework provides meaningful outcomes, it can be effectively replaced by more advanced techniques. (10.1063/5.0274535)
  DOI : 10.1063/5.0274535
• Une innovation institutionnelle
  
  • Colin Laure
  Le Libellio d'AEGIS, Libellio d'AEGIS, 2025, 21 (2), pp.39-45.