Analysis and approximation of the velocity tracking problem for Navier-Stokes flows with distributed control

We consider the mathematical formulation, analysis, and the numerical solut ion of a time-dependent optimal control problem associated with the trackin g of the velocity of a Navier-Stokes ow in a bounded two-dimensional domain through the adjustment of a distributed control. The existence of optimal solutions is proved and the first-order necessary conditions for optimality are used to derive an optimality system of partial differential equations whose solutions provide optimal states and controls. Semidiscrete-in-time a nd fully discrete space-time approximations are defined and their convergen ce to the exact optimal solutions is shown. A gradient method for the solut ion of the fully discrete equations is examined, as are its convergence pro perties. Finally, the results of some illustrative computational experiment s are presented.