  In this paper, we discuss selected adjoint approaches for the turbulent flow
control. In particular, we focus on the application of adjoint solvers for the
scope of noise reduction, in which flow solutions are obtained by large eddy
and direct numerical simulations. Optimization results obtained with round and
plane jet configurations are presented. The results indicate that using large
control horizons poses a serious problem for the control of turbulent flows due
to existence of very large sensitivity values with respect to control
parameters. Typically these sensitivities grow in time and lead to arithmetic
overflow in the computations. This phenomena is illustrated by a sensitivity
study performed with an exact tangent-linear solver obtained by algorithmic
differentiation techniques.
