Giovedì 28 novembre alle ore 14.30, presso la sala riunioni al secondo piano dell’edificio MO27, la Dott.ssa Alienor Riviere (Università Sorbonne) terrà il seminario dal titolo: "Bubble deformations and breakup in a turbulent flow".

Abstract:

In turbulent flows, bubble fate is controlled by the ratio between inertia and capillarity, namely the Weber number. There exists a critical Weber number which separates, in average, breaking from non-breaking bubbles. However, this limit is only defined in a statistical sense as it can happen that an a priori stable bubble encounters a large velocity or pressure fluctuation and breaks. In addition, real flows are rarely homogeneous and stationary. 

Using numerical simulations, we aim at quantifying the probability for a bubble to break in a given time window. To do so, we first study bubble deformations in a simplified flow geometry representative of the local flow geometry around bubbles: the uniaxial straining flow. 

We show that most of the dynamics can be reproduced by a 1D non linear oscillator on the oblate-prolate deformation mode. 

We then extend these results to a turbulent flow, by running direct numerical simulations of a single bubble in an homogeneous and isotropic turbulent flow. Similarly, we show that a 1D model is sufficient to describe most of bubble deformations, as well as predicting bubble lifetime.