from the conferences organized by TANGER Ltd.
Process stability is essential to produce high quality homogeneous zinc coatings at continuous galvanizing lines. In order to be able to predict the zinc film thickness after gas jet wiping, the adhered film thickness and its formation before the wiping process has to be known. For this reason, the Volume of Fluid (VOF) multiphase model considering surface tension effects together with the RNG k-ε and Large Eddy Simulation (LES) turbulence model were applied. For validation, the simulation results were compared with the theoretically predicted film thickness of Landau, Levich and Deryaguin (LLD) for static bath conditions. It was found out that up to a certain strip withdrawal speed, the RNG k-ε turbulence model shows good agreement with the theoretically predicted film thickness. For higher strip withdrawal speeds, as usually operated at continuous galvanization lines, the theoretical film thickness can only be achieved by applying the LES turbulence model. Furthermore, it is demonstrated, that changing the flow conditions, from a static bath to actual flow conditions inside a zinc bath, highly influences the local flow at the meniscus region. The flow near the meniscus and the meniscus movement itself affect the film thickness on the strip below the gas jet wiping nozzles. Therefore, controlling the flow near the meniscus region would lead to a better process stability for the gas-jet wiping process.
Keywords: Volume of Fluid (VOF), Large Eddy Simulation (LES), galvanizing, zinc bath, thin film, meniscus© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.