On the dynamics and breakup of a bubble immersed in a turbulent flow
Article dans une revue avec comité de lecture
Experimental investigations of the dynamics of a deformable bubble rising in a uniform turbulent flow are reported. The turbulence is characterized by fast PIV. Time-resolved evolutions of bubble translation, rotation and deformation are determined by three-dimensional shape recognition from three perpendicular camera views. The bubble dynamics involves three mechanisms fairly decoupled: (i) average shape is imposed by the mean motion of the bubble relative to liquid; (ii) wake instability generates almost periodic oscillations of velocity and orientation; (iii) turbulence causes random deformations that sometimes lead to breakup. The deformation dynamics is radically different from that observed in the absence of a significant sliding motion due to buoyancy. Large deformations that lead to breakup are not axisymmetric and correspond to elongations in the horizontal direction. The timescale of decay of shape oscillations is of the same order as their natural frequency f2, so that breakup always results from the interaction with a single turbulent eddy. This overdamping causes the statistics of large deformations and the statistics of breakup identical to the statistics of turbulence. The bubble response time f2 however controls the duration of individual breakup events.
Showing items related by title, author, creator and subject.
Article dans une revue avec comité de lectureZAARAOUI, Abdelkader; RAVELET, Florent; MARGNAT, Florent; KHELLADI, Sofiane (Elsevier, 2013)A prototype device for measuring the volumetric flow-rate by counting vortices has been designed and realized. It consists of a square-section pipe in which are placed a two-dimensional bluff body and a strain gauge force ...
A Comparative Study of Mixed Resolved–Unresolved CFD-DEM and Unresolved CFD-DEM Methods for the Solution of Particle-Laden Liquid Flows Article dans une revue avec comité de lectureKURUNERU, Sahan Trushad Wickramasooriya; MARECHAL, Ewen; DELIGANT, Michael; SAURET, Emilie; KHELLADI, Sofiane; RAVELET, Florent; SAHA, Suvash Chandra; GU, Yuantong (Springer Verlag, 2018)The exorbitant economic and environmental cost associated with fouling propels the need to develop advanced numerical methods to accurately decipher the underlying phenomena of fouling and multiphase fluid transport. The ...
Effects of axial rectangular groove on turbulent Taylor-Couette flow from analysis of experimental data Article dans une revue avec comité de lectureSODJAVI, Kodjovi; RAVELET, Florent; BAKIR, Farid (Elsevier, 2018)The relationship between a rough or structured surface topology and its hydraulic resistance was analysed in the case of fully turbulent Taylor-Couette flow at fixed radii ratio η = 0.9375 and for Reynolds numbers Re i ...
Experimental investigation of an actively controlled automotive cooling fan using steady air injection in the leakage gap Article dans une revue avec comité de lectureAZZAM, Tarik; PARIDAENS, Richard; RAVELET, Florent; KHELLADI, Sofiane; OUALLI, Hamid; BAKIR, Farid (SAGE Publications, 2017)In an axial fan, a leakage flow driven by a pressure gradient between the pressure side and the suction side occurs in the gap between the shroud and the casing. This leakage flow is in the opposite direction to the main ...
Influence of design parameters on the global performances of low-speed counter-rotating axial-flow fans Communication avec acteWANG, Juan; RAVELET, Florent; BAKIR, Farid (2014)The present work aims at experimentally investigating the effects of some parameters on the performances of a counter-rotating stage, and on the instationary flow between the rotors. Three counter-rotating fans, which have ...