  In this paper we consider optimal control of nonlinear time-dependent fluid
structure interactions. To determine a time-dependent control variable a BFGS
algorithm is used, whereby gradient information is computed via a dual problem.
To solve the resulting ill conditioned linear problems occurring in every time
step of state and dual equation, we develop a highly efficient monolithic
solver that is based on an approximated Newton scheme for the primal equation
and a preconditioned Richardson iteration for the dual problem. The performance
of the presented algorithms is tested for one 2d and one 3d example
numerically.
