MultiFlow is a fully coupled 2 and 3 dimensional viscous multiphase flow solver which can be employed to solve different models applicable to multiphase flows. MultiFlow employs momentum weighted interpolation to determine analytical expressions for the cell face velocities which are employed in the multiphase continuity equation in a collocated variable arrangement. A special approach is adopted for the momentum weighted interpolation to handle large source terms, volume fractions, and gradients of these. The resulting linearized equations are solved in a fully coupled manner. This enables a very efficient solution of the equations governing flows with particles, interfaces, droplets or separated flows.
There are several solving modules inside Multiflow:
 Fully coupled finite volume Computational Fluid Dynamics (CFD) solver for various sets of singlephase or multiphase governing equations.
 Direct Numerical Simulation (DNS) and several Large Eddy Simulation (LES) models, including Smagorinsky, WALE and several dynamic models.
 Hardsphere, softsphere and hybrid distinct element models to describe the behaviour of a large number of individual particles.
 Various volume of fluid, levelset and surfacetension implementations.
 Triangulation, deformation and moving of objects or interfaces.
 An accurate and efficient Quaternion solver for arbitrary objects.
All modules are fully parallel.
Fully Coupled Solver
The main advantage of a fully coupled approach is an increased robustness due to the implicit treatment of the pressure velocity coupling. Although the equations describing multiphase flows appear similar to singlephase flow equations, their nature is often much more difficult due to the presence of volume fractions, large source terms, and gradients of these as well as of density. This makes the requirement for a robust solving approach even more desirable.
A MultiScale Approach
MultiFlow has true multiscale capabilities: it can determine the behaviour of individual particles and interfaces, by fully resolving them. The next step is to resolve the behaviour of many particles or droplets. Finally, MultiFlow also has the capabilities of solving multiple sets of EulerianEulerian equations, including a full PDF approach, allowing for the prediction of large scale multiphase flows.
The pressure on a disc falling in a box filled with a fluid

Behaviour of individual particles in a Wurstertype fluidized bed
