*recruitment talk* we present a new approach to cfd and computational turbulence modeling using adaptive stabilized galerkin finite element methods with duality based a posteriori error control for chosen output quantities of interest, with the output based on the exact solution to the navier-stokes equations, thus circumventing introducing and modeling reynolds stresses in averaged navier-stokes equations. we refer to our methodology as adaptive dns/les, where automatically by adaptivity certain features of the flow are resolved in a direct numerical simulation dns, while certain other small scale turbulent features are left unresolved in a large eddy simulation les. the stabilization of the galerkin method giving a weighted least square control of the residual acts as the subgrid model in the les. the a posteriori error estimate takes into account both the error from discretization and the error from the subgrid model. a crucial observation from computational examples is that the contribution from subgrid modeling in the a posteriori error estimation can be small, making it possible to simulate aspects of turbulent flow without accurate modeling of reynolds stresses. using the a posteriori error estimates we further consider the question of uniqueness of weak solutions to the navier-stokes equations, where we give computational evidence of both uniqueness and non-uniqueness in outputs of weak solutions.