MultiFlow consists of  a coupled balanced-force numerical framework for single- and multi-phase flows at all speeds on unstructured meshes, including the incompressible, weakly compressible and fully compressible flow regimes. This framework enables the simulation of creeping, laminar and turbulent flows at any Mach number (sub-, trans-, super- and hypersonic flows) in complex geometries. The coupled numerical framework provides a strong, implicit pressure velocity coupling and accurately accounts for source terms using a novel balanced-force discretisation, which is of distinct advantages in flows with large source terms, such as multiphase flows or porous media, reduces errors caused by a force imbalance at the interface to solver tolerance and the fully-coupled methodology provides a strong pressure-velocity coupling.

We have successfully applied this pioneering numerical framework to a range of applications and flow regimes. In interfacial flows, for instance, the strong pressure-velocity coupling as well as the balanced-force discretisation allows us to accurately and robustly simulate fluid pairs with arbitrarily large density difference and surface tension, a currently unparalleled capability. With regards to compressible flows, the pressure-based formulation of the numerical framework enables us to simulate compressible flows of all Mach numbers on unstructured meshes and in complex geometries. In multi-phase flow problems, this enables the efficient, stable and accurate prediction of such flows in the Eulerian-Lagrangian or Eulerian-Eulerian frameworks.