Computational Modeling of Isothermal Flow Patterns: Effect of Surface Wettability at Different Scales
Natan Padoin1; Alan Zago de Souza1; Cíntia Soares1
1 Universidade Federal de Santa Catarina
doi:10.20906/CPS/CILAMCE2015-0512
Resumo
Surfaces can be classified as wettable or nonwettable, depending if the angle of a liquid phase poured on it is smaller or greater than 90º, respectively, at the triple line among the gas-liquid-solid phases. This parameter has strong influence on multiphase flow in channels, especially at reduced scales. As a matter of fact, while at the macroscale the surface to volume ratio is small and, thus, the influence of the bulk properties is significant, when microscale flow is considered the influence of the solid-fluid interface at the walls should not be neglected, as it can even represent the main phenomenon involved. In this scale, the contact angle may influence the flow pattern developed in the channel (e.g., stratified, slug, bubble, etc.), which, by its turn, exert strong influence on the pressure drop and the interfacial area available for heat and mass transfer, for instance. Therefore, the contact angle can be, at least indirectly, a key parameter in the design and analysis of these systems. The numerical simulation of the wettability effect on multiphase flow is a complex task. Several computational methods based on CFD techniques have been applied to take into account the influence of the contact angle on the flow. In fact, the frontiers of validity of specifying a static contact angle and the requirement of a dynamic contact angle as well as the feasibility of the non-slip boundary condition at the triple line are matter of intense debate in the current literature. This makes the numerical evaluation of the contact angle effect on multiphase flow an interesting topic for deep investigation, considering the abundance of numerical methods and advanced computational resources available nowadays. Based on this scenario, the aim of this study was to apply commercial CFD packages, e.g. ANSYS Fluent (finite volume method) and COMSOL Multiphysics (finite elements method), to the evaluation of the effect of contact angle on multiphase flow in a multi-scale approach. Experimental data was collected from the
Palavras-chave: Surface wettability; CFD; Contact angle; Multiphase flow