Methodenvergleich bei der Modellierung und Simulation von bewegten Grenzflächen und Nichtgleichgewichtsprozessen in Tropfen- und Filmsystemen
Final Report Abstract
In this report, a comparison between two methods involving free surfaces, namely the VoF method and the LS method, is presented. Two different test cases have been selected for the comparison. The first one is the study of the Kelvin-Helmholtz instability in two horizontal liquid layers, while the second one is the rising movement of a toluene droplet into a continuous aqueous phase. All the simulations are carried out with commercial CFD tools, namely CFX 5.7.1 with the implemented VoF method and Comsol Multiphysics 3.3a from COMSOL AB with the implemented LS method. The movement of the interface due to the Kelvin-Helmholtz instability can be captured accurately by both methods. In the simulation carried out using the VoF method, only minor smearing of the interface can be observed. The wave development agrees well with experimental and simulation results found in the literature. Similar results are obtained using the LS method. Therefore, for the two-layer flow, both methods are capable to capture the interface movement. The second case study is dedicated to the movement of a toluene droplet in a continuous aqueous phase. In all simulations carried out with the VoF method implemented in CFX 5.7.1, an extensive soft smearing of the toluene interface is visible. This non-physical trace appears in the computational domain, because the VoF function does not converge properly. For this case, the LS method, as it is implemented in Comsol Multiphysics, appears advantageous compared to the VoF method in CFX 5.7.1, as it does not show significant interface smearing. Droplet size and shape is in a good agreement with experimental results. For rigorous mass transfer studies, accurate resolution of the velocity field is essential. Due to the extensive smearing, it is hardly possible to perform rigorous mass transfer calculations using the VoF method as it is implemented in CFX 5.7.1 tool. Comsol Multiphysics appears to be advantageous as compared to CFX 5.7.1 for the examination of mass transfer and reaction in two phase flows. However, further investigations should be carried out.
Publications
- Hydrodynamics and mass transfer on single droplets: moving grid against volume of fluid. Proc. PRES'2006 9th Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction, Prague (Czech Republic), August 2006
T Atmakidis, S Burghoff & E Y Kenig
- A study on hydrodynamics and mass transfer of moving liquid layers using computation fluid dynamics. Proc. ESCAPE-17 European Symposium on Computer Aided Process Engineering, Bucharest (Romania), May 2007
T Atmakidis & E Y Kenig
