Deriving closures for bubbly flows using direct numerical simulations

摘要: CFD modeling of dispersed multiphase flows can be quite challenging because the wide range time- and length-scales involved. A modern methodology to bridge different scales is multi-scale modeling, which involves applying (types of) models describe phenomena prevailing at time length scales. This approach requires however, closure equations for unresolved sub-grid in higher level models. These closures principle obtained from analytical theory, experiments direct numerical simulations (DNS), each with their own strong weak points. Analytical theory limited idealized situations, instance spherical bubbles limit high Reynolds numbers, while are timeconsuming, costly easily influenced by disturbances contaminations often not all relevant quantities measured simultaneously desired accuracy. third relatively new path use DNS, restricted any situation nor suffers experimental difficulties. One strongest points freedom change physical properties or other parameters (geometry, operating parameters, etc.) will study influence independently great detail, having information on variables (such as flow field, pressure available. The objective this thesis was improve a 3D Front Tracking model it obtain drag, lift virtual mass forces acting single rising an initially quiescent infinite liquid. Using periodic boundary conditions, also neighboring (referred ‘swarm effects’) drag force studied. In addition, dedicated have been performed validate results bubbles.