MultiFlow uses a novel type of implicit immersed boundary (IB) method to resolve the flow structured surrounding an interface.
An Immersed Boundary technique is used to efficiently take into account the existence of interfaces or surfaces within the fluid domain. The flow domain can consist of a simple mesh, wheres the interface or surface can be arbitrary. There is a separate surface triangle grid for the boundary (or interface) and a separate grid for the fluid. The interfaces, surfaces, or bodies are triangulated using the MultiFlow Triangulation Library (MFTL). The picture below shows the surface triangulation mesh for two bodies in a flow
Two triangulated bodies in a flow
The methods developed and implemented in MultiFlow are tree-dimensional and second order accurate in space and time. The methods constrain the velocity of the fluid to a specified velocity exactly at the surface of any body immersed in the fluid flow. The velocity is constrained by an implicitly formulated immersed boundary condition (IBC). In MultiFlow, three different discretization schemes of the IBC have been implemented. In contrast to most other immersed boundary methods, a special treatment is adopted to exclude any fictitious velocity field from the governing equations. The method can be used to study the interaction of interfaces, particles or other types of surfaces in a flow.
The fluid flow around a disc
Streamlines around an ellipsoid
Averaged flow around a tilted disc