# Modelling and implementation of surface tension effects into CFD wall film module

Baleta, Jakov and Vujanović, Milan and Duić, Neven and Pachler, Klaus (2014) Modelling and implementation of surface tension effects into CFD wall film module. = Modelling and implementation of surface tension effects into CFD wall film module. In: 1st South East European Conference on Sustainable Development of Energy, Water and Environment Systems - SEE SDEWES Ohrid 2014, 29.06.-03.07.2014., Ohrid, Makedonija.

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## Abstract

The behaviour of a shear-driven thin liquid wall film is of interest in many engineering applications. Numerical simulations are becoming valuable tool for detailed understanding of complex flow characteristics and transport phenomena appearing in such kind of multiphase flows, since experimental measurements are infeasible or too expensive. Given assumptions regarding thin liquid films, Navier-Stokes equations are converted to wall film governing equations which are modelled with a 2D finite volume method in the AVL Fire wall film module. The main limitations of a continuous finite volume approach of the film model are at boundary edges of the liquid phase - the approximation of constant film height over the control volume does not permit accurate reconstruction of interface characteristics. This scattering of liquid film causes high numerical diffusion and an overestimation of evaporation, which is proportional to the area of contact with gas. In order to overcome those issues, mathematical model for description of surface tension effects was developed and implemented into CFD code. Although in literature can be found alternative approaches, such as volume of fluid method (VOF), level set methods etc., Eulerian based description of wall film used in Fire enables incorporation of surface tension effects in pressure term of liquid wall film momentum equation as the simplest and most efficient way taking into account computational resources. After implementation of the above described mathematical model, next step was validation through selected case for which there is analytical description. Improved model of liquid wall film behaviour developed within this paper is important contribution in continuous process where constant improvement of accuracy of the physical models used in CFD is conditio sine qua non in order to comply with the ever increasing requirements of the industry.

Item Type: Conference or Workshop Item (Lecture) wall film, computational fluid dynamics, surface tension, droplet spreading, capillary force TECHNICAL SCIENCE > Mechanical Engineering 500 Department of Energy, Power Engineering and Environment > 510 Power Engineering and Energy Management Chair No No 06 Apr 2016 09:39 27 Apr 2016 09:35 http://repozitorij.fsb.hr/id/eprint/5439

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