Abstract:We consider the preconditioning of linear systems arising from four convection-diffusion model problems: scalar convection-diffusion problem, Stokes problem, Oseen problem, and NavierStokes problem. For these problems we identify an explicit Kronecker product structure of the coefficient matrices, in particular for the convection term. For the latter three model cases, the coefficient matrices have a 2 × 2 block structure, where each block is a Kronecker product or a summation of several Kronecker products. We use these structures to design a diagonal block preconditioner, a tridiagonal block preconditioner and a constraint preconditioner. The constraint preconditioner can be regarded as the modification of the tridiagonal block preconditioner and of the diagonal block preconditioner based on the cell Reynolds number. For this reason, the constraint preconditioner is usually more efficient. We also give numerical examples to show the efficiency of these preconditioners.