MultiFlow

MultiFlow is a fully coupled 2 and 3 dimensional viscous multi-phase 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 single-phase or multi-phase governing equations.
• Direct Numerical Simulation (DNS) and several Large Eddy Simulation (LES) models, including Smagorinsky, WALE and several dynamic models.
• Hard-sphere, soft-sphere and hybrid distinct element models to describe the behaviour of a large number of individual particles.
• Various volume of fluid, level-set and surface-tension 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 single-phase 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 Multi-Scale Approach

MultiFlow has true multi-scale 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 Eulerian-Eulerian equations, including a full PDF approach, allowing for the prediction of large scale multiphase flows.