Characterization of Bubble Shapes in Non‐Newtonian Fluids by Parametric Equations

Based on experiments with single air bubbles rising in stagnant non-Newtonian fluids, an innovative model containing the aspect ratio (E) and two parameters (alpha, beta) was proposed and proved to be capable of characterizing the bubble shape from spherical/ellipsoidal to prolate/oblate-tear with good accuracy. Several impacts on bubble deformation were investigated, involving the rheological properties of the fluids and different forces exerted on the bubble, which were quantified by multiple dimensionless numbers (e.g., Reynolds, Eotvos, and Deborah number). Within a wide range, the empirical correlations were obtained for parameter beta, and between alpha and beta. Together with the shape model, a complete system was set up for bubble shape characterization and prediction that will provide new ideas for future studies on bubble hydrodynamics

Attenuation of road dust emissions caused by industrial vehicle traffic

International audienc

Numerical investigation of swirling flow in cylindrical cyclones

International audienceThis paper constitutes a preliminary study of the two-phase flow in a Gas-Liquid Cylindrical Cyclone (GLCC 1) separator. A GLCC consists in a vertical pipe with a downward inclined tangential inlet. The incoming flow forms a swirling motion producing a centrifugal force. The gas and liquid are thus separated due to both centrifugal and gravity forces. Therefore the separation efficiency is higher than for conventional vessel type separators, allowing more compactness. In this study, the aim is to better understand the swirling hydrodynamics of this separator via CFD simulations. Therefore, the single-phase hydrodynamics is calculated for swirling flows generated by means of tangential injection(s) in a straight pipe. Geometry and flow conditions are chosen according to the experimental study of Erdal (2001a), who performed local measurements of the axial and tangential velocities. BANS, URANS and LES simulations are carried out using different turbulence models and different near wall treatments. Among the Reynolds Averaged Navier-Stokes (RANS) models, the high-Reynolds realizable kappa-epsilon model performs the best for predicting the local mean axial and tangential velocities. Its results are as good as the LES ones when the fluid is injected through only one inlet, while LES predicted flow is closer to the experimental one for two inlets. Numerical results also show that, contrary to the common approximation of the literature, the radial velocity magnitude is not negligible. The vortex core precession is well predicted by the simulations, which show that its direction is the opposite of the swirl one. We think that the growth of the turbulence kinetic energy in the core of the flow is directly linked to this phenomenon. Finally computations are conducted to investigate the effect of the inlet geometry on the cyclone hydrodynamics. According to simulations, the rectangular inlet performs better than a circular one, since it reduces the vortex distortion, which is supposed to improve the separation efficiency

Estimation of the atmospheric corrosion on metal containers in industrial waste disposal

Solid industrial waste are often stored in metal containers filled with concrete, and placed in well-aerated warehouses. Depending on meteorological conditions, atmospheric corrosion can induce severe material damages to the metal casing, and this damage has to be predicted to achieve safe storage. This work provides a first estimation of the corrosivity of the local atmosphere adjacent to the walls of the container through a realistic modeling of heat transfer phenomena which was developed for this purpose. Subsequent simulations of condensation/evaporation of the water vapor in the atmosphere were carried out. Atmospheric corrosion rates and material losses are easily deduced. For handling realistic data and comparison, two different meteorological contexts were chosen: (1) an oceanic and damp atmosphere and (2) a drier storage location. Some conclusions were also made for the storage configuration in order to reduce the extent of corrosion phenomena