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Accueil > Evénements Scientifiques > Conf’luences > Conf’luences 2011 > Conf’luence J. Gordillo le 9 juin

Conf’luence J. Gordillo le 9 juin

30 mai 2011

Slender body theory for tip streaming : the formation of emulsions composed by micron-sized drops
Jeudi 9 juin à 10h30
Amphithéâtre Nougaro
J. Gordillo, Université de Séville

Résumé :
In the present talk we show that submicron sized drops can be generated through a coflow of two immiscible streams at Re=0 when the capillary number based on the outer flow properties exceeds a certain threshold value of order unity. A tiny and long jet which subsequently breaks into drops is formed when the capillary number is above the threshold and whenever the inner to outer flow rate ratio is sufficiently small. The breakup of such jets into drops occurs through a capillary instability. The shapes of the jets for any values of the viscosity ratio, capillary number and flow rate ratio is very well predicted thanks to a slender body theory. Moreover, the sizes of the drops can be predicted by a stability analysis which is an extension of the classical work of Tomotika. We also show that concentrated emulsions composed by drops with sizes below 5 micron showing a crystal-like structure, can be efficiently produced in this way. However, since the method is not valid for the generation of monodisperse bubbles, we present an alternative procedure that makes use of a strong favourable pressure gradient to generate monodisperse bubbles with sizes down to 5 microns that can be applied as contrast agents.

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