VOF simulations of the contact angle dynamics during the drop spreading: Standard models and a new wetting force model

Article English OPEN
Malgarinos, I. ; Nikolopoulos, N. ; Marengo, M. ; Antonini, C. ; Gavaises, M. (2014)

Introduction\ud In this study,a novel numerical implementation for the adhesion of liquid droplets impacting normally on solid dry surfaces is presented. The advantage of this new approach, compared to the majority of existing models, is that the dynamic contact angle forming during the surface wetting process is not inserted as a boundary condition, but is derived implicitly by the induced fluid flow characteristics (interface shape) and the adhesion physics of the gas-liquid-surface interface (triple line), starting only from the advancing and receding equilibrium contact angles. These angles are required in order to define the wetting properties of liquid phases when interacting with a solid surface. \ud \ud Methodology\ud The physical model is implemented as a source term in the momentum equation of a Navier-Stokes CFD flow solver as an "adhesion-like" force which acts at the triple-phase contact line as a result of capillary interactions between the liquid drop and the solid substrate. The numerical simulations capture the liquid-air interface movement by considering the volume of fluid (VOF) method and utilizing an automatic local grid refinement technique in order to increase the accuracy of the predictions at the area of interest, and simultaneously minimize numerical diffusion of the interface. \ud \ud Results\ud The proposed model is validated against previously reported experimental data of normal impingement of water droplets on dry surfaces at room temperature. A wide range of impact velocities, i.e. Weber numbers from as low as 0.2 up to 117, both for hydrophilic (θadv = 10° - 70°) and hydrophobic (θadv = 105° - 120°) surfaces, has been examined. Predictions include in addition to droplet spreading dynamics, the estimation of the dynamic contact angle; the latter is found in reasonable agreement against available experimental measurements. \ud \ud Conclusion\ud It is thus concluded that theimplementation of this model is an effective approach for overcoming the need of a pre-defined dynamic contact angle law, frequently adopted as an approximate boundary condition for such simulations. Clearly, this model is mostly influential during the spreading phase for the cases of low We number impacts (We <80) since for high impact velocities, inertia dominates significantly over capillary forces in the initial phase of spreading.
  • References (10)

    Kim, J., Spray cooling heat transfer: The state of the art. International Journal of Heat and Fluid Flow, 2007. 28(4): p. 753-767.

    Kandlikar, S.G. and A.V. Bapat, Evaluation of Jet Impingement, Spray and Microchannel Chip Cooling Options for High Heat Flux Removal. Heat Transfer Engineering, 2007. 28(11): p. 911-923.

    Han, Z., Z. Xu, and N. Trigui, Spray/wall interaction models for multidimensional engine simulation. International Journal of Engine Research, 2000. 1(1): p. 127-146.

    Zhao, F., M.C. Lai, and D.L. Harrington, Automotive spark-ignited direct-injection gasoline engines. Progress in Energy and Combustion Science, 1999. 25(5): p. 437-562.

    Pasandideh-Fard, M., et al., Splat shapes in a thermal spray coating process: Simulations and experiments. Journal of Thermal Spray Technology, 2002. 11(2): p. 206-217.

    NASA technical paper ; 210031., ed. N.G.R. Center2000, [Cleveland, Ohio] : [Springfield, Va: National Aeronautics and Space Administration, Glenn Research Center ; National Technical Information Service, distributor.

    Langmuir, 2013. 29(52): p. 16045-16050.

    Faustini, M., et al., Hydrophobic, Antireflective, Self-Cleaning, and Antifogging Sol−Gel Coatings: An Example of Multifunctional Nanostructured Materials for Photovoltaic Cells. Chemistry of Materials, 2010. 22(15): p. 4406-4413.

    Young, T., An Essay on the Cohesion of Fluids. Philosophical Transactions of the Royal Society of London, 1805. 95: p. 65-87.

    Worthington, A.M., On the Forms Assumed by Drops of Liquids Falling Vertically on a Horizontal Plate. Proceedings of the Royal Society of London, 1876. 25(171-178): p. 261-272.

  • Related Research Results (1)
  • Metrics
    views in OpenAIRE
    views in local repository
    downloads in local repository

    The information is available from the following content providers:

    From Number Of Views Number Of Downloads
    City Research Online - IRUS-UK 0 57
Share - Bookmark