162,941 research outputs found
Analytical and numerical stability analysis of Soret-driven convection in a horizontal porous layer
No full textWe present an analytical and numerical stability analysis of Soret-driven convection in a porous cavity saturated by a binary fluid. Both the mechanical equilibrium solution and the monocellular flow obtained for particular ranges of the physical parameters of the problem are considered. The porous cavity, bounded by horizontal infinite or finite boundaries, is heated from below or from above. The two horizontal plates are maintained at different constant temperatures while no mass flux is imposed. The influence of the governing parameters and more particularly the role of the separation ratio, characterizing the Soret effect and the normalized porosity, are investigated theoretically and numerically. From the linear stability analysis, we find that the equilibrium solution loses its stability via a stationary bifurcation or a Hopf bifurcation depending on the separation ratio and the normalized porosity of the medium. The role of the porosity is important, when it decreases, the stability of the equilibrium solution is reinforced. For a cell heated from below, the equilibrium solution loses its stability via a stationary bifurcation when the separation ratio >0(Le,), while for 0, while a stationary or an oscillatory bifurcation occurs if mono the monocellular flow loses stability via a Hopf bifurcation. As the Rayleigh number increases, the resulting oscillatory solution evolves to a stationary multicellular flow. For a cell heated from above and <0, the monocellular flow remains linearly stable. We verified numerically that this problem admits other stable multicellular stationary solutions for this range of parameters
Jacques-Louis Soret
No full textJACQUES-LOUIS SORET
Jacques-Louis Soret ( - )
Cover ( - )
Exlibris: Bibliothek der Sekundogenitur des Grossherzoglich Sächsischen Hauses ( - )
Portrait: Jacques-Louis Soret ( - )
Titelseite (1)
Notice sur la vie et les travaux de J.-L. Soret (3)
Appendice (36
Sur la polarisation rotatoire du quartz
No full textJ.-L. Soret et Edouard SarasinSonderdruck aus: Archives des sciences de la Bibliothèque universell
Analytical and numerical stability analysis of Soret-driven convection in a horizontal porous layer: the effect of conducting bounding plates
No full textThe aim of this study was to investigate the effect of conducting boundaries on the onset of convection in a binary fluid-saturated porous layer. The isotropic saturated porous layer is bounded by two impermeable but thermally conducting plates, subjected to a constant heat flux. These plates have identical conductivity. Moreover, the conductivity of the plates is generally different from the porous layer conductivity. The overall layer is of large extent in both horizontal directions. The problem is governed by seven dimensionless parameters, namely the normalized porosity of the medium ε, the ratio of plates over the porous layer thickness δ and their relative thermal conductivities ratio d, the separation ratio δ, the Lewis number Le and thermal Rayleigh number Ra. In this work, an analytical and numerical stability analysis is performed. The equilibrium solution is found to lose its stability via a stationary bifurcation or a Hopf bifurcation depending on the values of the dimensionless parameters. For the long-wavelength mode, the critical Rayleigh number is obtained as Racs=12(1+2dδ )/[1+ψ (2dδLe+Le+1)] and kcs=0 for ψ> ψ uni> 0. This work extends an earlier paper by Mojtabi and Rees (2011 Int. J. Heat Mass Transfer 54 293-301) who considered a configuration where the porous layer is saturated by a pure fluid
[Report to Chief J. E. Curry, by an unknown author #1]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
[Report to Chief J. E. Curry, by an unknown author #2]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
Effect of solid thermal conductivity and particle-particle contact on effective thermodiffusion coefficient in porous media
No full textTransient mass transfer associated to a thermal gradient through a saturated porous medium is studied experimentally and theoretically to determine the effect of solid thermal conductivity and particle-particle contact on thermodiffusion processes. In this study, the theoretical volume averaging model developed in a previous study has been adopted to determine the effective transport coefficients in the case of particle-particle contact configurations. The theoretical results revealed that the effective thermodiffusion coefficient is independent of the thermal conductivity ratio for pure diffusive cases. In all cases, even if the effective thermal conductivity depends on the particle-particle contact, the effective thermodiffusion coefficient remains independent of the solid phase connectivity. We also found that the porosity can change the impact of dispersion effects on the thermodiffusion coefficients. For large values of the thermal conductivity contrast, dispersion effects are negligible and the effective thermal conductivity coefficients are the same as the ones for the pure diffusion case. Experimental results obtained for the purely diffusive case, using a special two-bulb apparatus, confirm the theoretical results. These results also show that, for non-consolidated porous media made of spheres, the thermal conductivity ratio has no significant influence on the thermodiffusion process for pure diffusion. Finally, the particle-particle contact also does not show a considerable influence on the thermodiffusion process
Evidence of large nonlinear magnetic effects in the paramagnetic phase of GaFeO3
No full textMagnetic susceptibility and magnetization measurements have been performed on a polycrystalline sample of GaFeO3 and compared with X-band electronic spin resonance (ESR) experiments. The persistence of nonlinear effects in the presence of relatively low external fields is observed far above the ferrimagnetic transition. The temperature evolution of the ESR spectra indicates the increase of spin-spin interactions accompanied by significant changes in the internal field as the nonlinear regime becomes more important. This suggests the existence of ferrimagnetic short-range spin correlations induced by the external field over a wide temperature range above the magnetic ordering transition
Soret fishnet metalens antenna.
No full textAt the expense of frequency narrowing, binary amplitude-only diffractive optical elements emulate refractive lenses without the need of large profiles. Unfortunately, they also present larger Fresnel reflection loss than conventional lenses. This is usually tackled by implementing unattractive cumbersome designs. Here we demonstrate that simplicity is not at odds with performance and we show how the fishnet metamaterial can improve the radiation pattern of a Soret lens. The building block of this advanced Soret lens is the fishnet metamaterial operating in the near-zero refractive index regime with one of the edge layers designed with alternating opaque and transparent concentric rings made of subwavelength holes. The hybrid Soret fishnet metalens retains all the merits of classical Soret lenses such as low profile, low cost and ease of manufacturing. It is designed for the W-band of the millimeter-waves range with a subwavelength focal length FL = 1.58 mm (0.5λ0) aiming at a compact antenna or radar systems. The focal properties of the lens along with its radiation characteristics in a lens antenna configuration have been studied numerically and confirmed experimentally, showing a gain improvement of ~2 dB with respect to a fishnet Soret lens without the fishnet metamaterial
DATA: hydrogen and ammonia flame speeds from different Soret diffusion models
No full textUnstretched laminar flame speeds (sL0) of hydrogen-air and ammonia/hydrogen-air flames
Each file contains a table with the raw flame speed data presented in the paper
T. Zirwes, A. Kronenburg, "Assessment of Approximate Soret Diffusion
Models for Hydrogen and Ammonia Combustion", Flow, Turbulence and Combustion (2025), https://doi.org/10.1007/s10494-025-00680-5
Each table is structured as follows:
The file name contains information about the fuel composition (either pure hydrogen, "H2", or ammonia/hydrogen at a 60/40 blend by volume, "60-NH3-40-H2"), the unburnt gas temperature (either 300K or 500K), the pressure (either 1atm or 5atm) and the reaction mechanism (Stagni et al. [1] for the ammonia-hydrogen flames and Li et al. [2], Burke et al [3] or Boivin et al [4] for pure hydrogen flames).
The columns contain:
Column 1: Equivalence ratio
Column 2: sL0 from the multicomponent model without Soret diffusion (m/s)
Column 3: sL0 from the multicomponent model with Soret diffusion (m/s)
Column 4: sL0 from the mixture-averaged model with the Chaptman&Cowling Soret model (m/s)
Column 5: sL0 from the mixture-averaged model with the Bartlett Soret model (m/s)
Column 6: sL0 from the mixture-averaged model with the Hirschfelder&Warnatz Soret model activated only for H and H2 (m/s)
[1] A. Stagni, S. Arunthanayothin, M. Dehue, O. Herbinet, F. Battin-Leclerc, P. Bréquigny, C. Mounaïm-Rousselle, T. Faravelli, "Low-and intermediate temperature ammonia/hydrogen oxidation in a flow reactor: Experiments and a
wide-range kinetic modeling", Chem. Eng. J. 471 (2023)
[2] J. Li, Z. Zhao, A. Kazakov, F.L. Dryer, "An updated comprehensive kinetic model of hydrogen combustion", Int. J. Chemical Kinetics 36, 566-575 (2004)
[3] M.P. Burke, M. Chaos, Y. Ju, F.L. Dryer, S.J. Klippenstein, "Comprehensive H2/O2 kinetic model for high-pressure combustion", Int. J. Chem. Kinetics 44(7), 444-474 (2012)
[4] P. Boivin, "Reduced-kinetic mechanisms for hydrogen and syngas combustion including autoignition", Phd, Universidad Carlos III de Madrid (2011)
</p
- …
