Professor Véronique Roig
Institut de Mécanique des Fluides de Toulouse, Université de Toulouse

10:45 AM - Conference Room

Abstract :

Bubbly flows are present in a lot of industrial applications. In bubble columns for chemical engineering the performance is often linked to the efficient mixing of the reagents dissolved in the liquid phase. In such flows, where strong two-way coupling between phases is present, the agitation induced by the bubbles in the liquid phase is complex to analyze and the elementary mechanisms for mixing have not been studied a lot.
In this talk, we will discuss recent results about the generic problem of the mixing of a low-diffusive dye in the agitation induced in the liquid phase by a homogeneous swarm of high-Re bubbles rising in a liquid otherwise at rest.
We will show that it is important to analyze the mixing, as the bubble-induced agitation resulting from wakes interactions, considering that the fluctuating motion of the liquid is a combination of two types of agitation: (i) an agitation induced by the mean wakes of the bubbles that is controlled by the random positioning of the bubbles and (ii) a turbulent agitation resulting from Navier-Stokes instability.
Mixing has been studied in our team in various experiments defined to contrast the various involved mechanisms: (i) mixing in a 3D bubble swarm, (ii) mixing in a bubble swarm confined in a Hele-Shaw cell and (iii) in a flow crossing a random array of fixed spheres. Generic results that have been obtained and that provide a better understanding of the specific mechanisms in bubbly flows will be discussed.

Mixing in 3D bubble swarm, in a confined Hele-Shaw cell, in a random array of spheres
 

Location : von Karman Institute, Chaussée de Waterloo 72, 1640 Rhode-St-Genèse, Conference Room