# Fluid Structure Interaction (FSI)

One of the rich features of AcuSolve lies in its ability to simulate FSI problems.

- Practical FSI (P-FSI)
- In P-FSI simulations, AcuSolve and the structural code are run separately. The Eigen solution obtained from a structural solver is projected onto the CFD mesh and used as boundary conditions to displace the fluid mesh. The mass, stiffness and damping arrays are also transferred from the structural model to flexible body in the CFD model, completing the inputs necessary to compute the structural deformation. P-FSI is preferred for simulations that have linear structural response (linear material properties and small mesh deformations).
- Direct Coupled FSI (DC-FSI)
- For applications involving a nonlinear structural response, AcuSolve is coupled at run time to a structural solver using the DC-FSI approach. The codes are run in tandem and exchange forces and displacements at each time step. This technique captures all nonlinearities in the structural model and can exploit the full capabilities of the structural solver. The DC-FSI technology within AcuSolve performs all projection and interpolation between the structural and CFD meshes without the use of any middleware. The supported structural solvers for AcuSolve include OptiStruct, Abaqus and MD-Nastran.