Colloids and Surfaces A: Physicochem. Eng. Aspects 386 (2011) 107–115 Contents lists available at ScienceDirect Colloids and Surfaces A: Physicochemical and Engineering Aspects jo ur nal homep a ge: www.elsevier.com/locate/colsurfa A computational fluid dynamics model using the volume of fluid method for describing the dynamics of spreading of Newtonian fluids Hocine Alla a , Somia Freifer a , Thibault Roques-Carmes b,∗ a Département de Physique, Faculté des Sciences, Université des Sciences et de la Technologie d’Oran (USTO-MB), BP 1505 El M’Naouar Bir el Djir 31000, Oran, Algeria b Laboratoire Réactions et Génie des Procédés, UPR 3349 CNRS, Nancy-University, 1 rue Grandville, BP 20451, 54001 Nancy Cedex, France a r t i c l e i n f o Article history: Received 5 April 2011 Received in revised form 6 July 2011 Accepted 7 July 2011 Available online 28 July 2011 Keywords: Spreading Dynamics Surfactant Simulation CFD Volume of fluid a b s t r a c t A numerical study is performed to describe the dynamics of drop spreading of glycerol–water mixtures with and without surfactant on hydrophilic glass surfaces. A computational fluid dynamics model (CFD), based on the volume of fluid technique (VOF), with piecewise linear interface calculations method (PLIC) for interface reconstruction, is applied to simulate the time evolution of spreading drops on solid surfaces (drop base radius and contact angle). Surface tension and wall adhesion phenomenon are included in the computational model. Numerical simulations with two-dimensional domains are sufficient to reproduce the key qualitative features observed in the experiments. The CFD simulations are quantitatively com- pared with previously published experimental results. The influence of different factors, such as viscosity, drop volume and non-ionic alkyl (8–16) glucoside (Plantacare 2000) surfactant concentration on the tem- poral evolution of the drop base radius is systematically investigated. More than 25 simulations have been performed in order to obtain detailed quantitative comparison and clear trends. We have shown, using several independent experiments, that the calculated results compare very well with experimental data for a large range of viscosity (0.02–1.15 Pa s), drop volume (8–60 L) and in the presence of surfactant. The accuracy of the model demonstrates that the influence of the physical–chemical properties of the liquid such as viscosity, volume and surface tension can be successfully simulated. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The dynamics of spreading is a very active area of research, not only for academic reasons, but also because many industrial and materials processing operations require the spreading of liq- uid on a solid. Although wetting has been studied for many years [1,2], many fundamental problems remain open, especially those related to the motion kinetics of the contact-line, particularly in the presence of surfactant [3,4]. However, significant advances have been made in the understanding of the factors that determine the rate at which solids may be wetted by pure liquids. Two princi- pal approaches are used to describe the dynamics of spontaneous spreading: the hydrodynamic [5–8] and the molecular-kinetic model [9,10]. The main difference between the models is the mode of energy dissipation. In the hydrodynamic model, the dissipa- tion of energy is controlled by the displacements of the molecules in the wedge-like region neighboring the contact-line, while the molecular-kinetic model emphasizes dissipation due to friction at the three-phase contact-line. The molecular-kinetic theory is ∗ Corresponding author. Tel.: +33 3 83 17 50 89; fax: +33 3 83 37 81 20. E-mail address: thibault.roques-carmes@ensic.inpl-nancy.fr (T. Roques-Carmes). well suited for describing the high velocity and large contact angle regime while the final stage of wetting is accurately described by the hydrodynamic model [11]. Each model can be described by a power law determining the time evolution of the drop base radius R(t) of the form R = K × t m . The power law exponents m are precisely identified for each regime [12,13]. However, only approx- imate expressions are available for the pre-exponential factor K [12,13]. In the general case, a succession of several different spread- ing regimes occurs during the time course of a drop [14,15]. Namely, a fast early-time stage characterized by a linear time-dependence of the base radius; (2) a molecular-kinetic stage at which the dom- inant contribution to dissipation comes from attachment of fluid molecules to a solid; (3) a kinetic stage at which the hydrodynamic dissipation dominates; and lastly, (4) an exponential relaxation to the equilibrium state. The different spreading regimes are linked one another by an intermediate regime which cannot be described by a power law [12,14]. Thus the present day ability to predict the dynamics of wetting and to model processes that are dependent on wetting is still significantly restricted [13]. It becomes then necessary to develop a numerical model in order to simulate the complex hydrodynamics of wetting. Sev- eral numerical methods of computational fluid dynamics (CFD) are available to simulate free-surface flows (flows with moving inter- faces). The volume of fluid technique (VOF) is one of the most 0927-7757/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfa.2011.07.006