### Fluid-structure interaction with a staged algorithm

*Mario Alberto Storti*

#### Abstract

A common approach to solving fluid-structure interaction problems is to solve each subproblem in a partitioned procedure where time and space discretization methods could be different. Such a scheme simplifies explicit/implicit integration and it is in favor of the use of different codes specialized on each sub-area. In this work a staggered fluid-structure coupling algorithm is considered. For each time step a "stage-loop" is performed. In the first stage a high order predictor is used for the structure state, then the fluid and the structure systems are advanced in that order. In subsequent stages of the loop each system uses the previously computed state of the other system until convergence. For weakly coupled problems a stable and efficient algorithm is obtained using one stage and an accurate enough predictor. For strongly coupled problems, stability is enhanced by increasing the number of stages in the loop. If the stage loop is iterated until convergence, a monolithic scheme is recovered. In addition, two items that are specially important in fluid structure problems are discussed, namely invariance of the stabilization terms and dynamic absorbing boundary conditions. Finally, numerical examples are presented.

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