“…Several well-established techniques have been proposed to enhance stability and accuracy of the optimal control problems governed by the steady convection diffusion equation, e.g., the streamline upwind/Petrov Galerkin (SUPG) finite element method [11], the local projection stabilization [5], the edge stabilization [27,51], and discontinuous Galerkin methods [32,52,53,54,55]. However, only few papers are published so far for unsteady optimal control problems governed by convection diffusion equations, e.g., the characteristic finite element method [14,15], the streamline upwind/Petrov Galerkin (SUPG) finite element method [30], the local discontinuous Galerkin (LDG) method [57], the nonsymmetric interior penalty Galerkin (NIPG) method [45], and the symmetric interior penalty Galerkin (SIPG) method [2].…”