Droplets formation in turbulent mixing of two immiscible fluids in a new type of static mixer T. Lemenand a , D. Della Valle b , Y. Zellouf a , H. Peerhossaini a,* a Thermofluids and Complex Flows Research Group, Laboratoire de Thermocin etique CNRS UMR 6607,  Ecole Polytechnique de l’Universit e de Nantes, rue Christian Pauc, B.P. 50609, Nantes Cedex 3, 44306, France b  Ecole Nationale d’Ing enieurs des Techniques des Industries Agricoles et Alimentaires, rue de la G eraudi  ere, B.P. 82225, Nantes 44322, France Received 28 January 2002; received in revised form 29 January 2003 Abstract The emulsification process in a static mixer high-efficiency vortex in turbulent flow is investigated. This new type of mixer generates coherent large-scale structures, enhancing momentum transfer in the bulk flow and hence providing favourable conditions for phase dispersion. The generation of the emulsion is de- scribed via a classical size-distribution function characterised by the Sauter diameter and a dispersion factor. Ó 2003 Elsevier Science Ltd. All rights reserved. Keywords: Emulsification; Encapsulation; Dispersion; Granulometry; Optical microscopy; Sauter diameter; Size distribution; Static mixer; Two-phase flow 1. Introduction The use of static mixers in the manufacture of emulsions or dispersions of immiscible fluids has received much attention over the last two decades thanks to recent progress in the hydrodynamics and the mixing performance of these systems. Process control and monitoring have been im- proved as well, especially in the chemical, petrochemical, food and cosmetics industries. Only a few manufacturers offer such equipment (Sulzer, Kenics, Optimix,...), however, and it is com- monly agreed that novel hardware is greatly needed to handle specific new processes. The objective of this study is to characterise the emulsification process achieved with a new static mixer commonly called HEV (high-efficiency vortex). The HEV design is based on curved International Journal of Multiphase Flow 29 (2003) 813–840 www.elsevier.com/locate/ijmulflow * Corresponding author. Tel.: +33-2-4068-3142; fax: +33-2-4068-3141. E-mail address: hassan.peerhossaini@polytech.univ-nantes.fr (H. Peerhossaini). 0301-9322/03/$ - see front matter Ó 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0301-9322(03)00032-6