Computational Fluid Structure Interaction - Computational Hemodynamics: Theory, Modelling and Applications - page 149

FSI coupling is characterised by the amount of repeated iterations between the
fluid and solid domain. Computationally, this refers to how many iterations are used
to reach convergence. A weak coupling is one that uses a minimum iteration while
a strong coupling uses a maximum. Physically this means that a weakly coupled
FSI is suitable for cases with minimal deformation between the fluid and structureal
domain, while a stronger coupling is needed for cases with more deformation.

5.6.3 Stability and Convergence

Stability at the fluid-solid interface is a big concern with FSI simulations, particu-
larly when the structure is very flexible and exhibits instabilities at the interface. In
two-way coupling, the fluid mesh deformation of is calculated by the displacement
diffusion algorithm. The connections between the nodes are modelled as springs
with different stiffness. This stiffness can change from node to node, and it is set
very high for nodes near boundaries. In the normal direction from the FSI interface,
the first ten nodes have displacements in the range of the boundary displacement.
This provides high quality meshes even in the boundary layer. Figure 5.42 shows
a comparison of non-deformed and deformed mesh for an idealized arterial vessel,
and in both cases, the mesh has a satisfactory quality.

Fig. 5.42 Comparison between non-deformed mesh and deformed mesh for an idealized arterial
vessel