A standard test case for two-phase flow of air being blown into the base of a column of water. The problem is transient and both fluids assumed
incompressible.
Physics and modelling
The mathematical model used in this simulation is the two-phase Eulerian model, where the phase-to-phase interaction is modelled. A phase
fraction () describes the state at all points in the column: 0 corresponding to water; 1 to air, the dispersed phase. The modelling involves solving
a phase fraction equation for , two momentum equations and a single pressure equation. The OpenFOAM two-phase model can uniquely deal with cases where in
a part of the domain only one fluid is present. Here, the solution resolves the free surface at the top of the liquid above which only the air is present: the model
incorporates both the two-phase and free surface modelling.
OpenFOAM solver
bubbleFoam and customised versions.
Animations
The animation shows the volume fraction field for the air and water. The plume is seen to oscillate from side to side rather than rise in a straight line;
The velocity of the water phase is faster than that of the rising bubbles and creates a recirculation zone around the plume. The free surface is well resolved.
(
) describes the state at all points in the column: 0 corresponding to water; 1 to air, the dispersed phase. The modelling involves solving
a phase fraction equation for 