  Boundary value problems based on the convection-diffusion equation arise
naturally in models of fluid flow across a variety of engineering applications
and design feasibility studies. Naturally, their efficient numerical solution
has continued to be an interesting and active topic of research for decades. In
the context of finite-element discretization of these boundary value problems,
the Streamline Upwind Petrov-Galerkin (SUPG) technique yields accurate
discretization in the singularly perturbed regime. In this paper, we propose
efficient multigrid iterative solution methods for the resulting linear
systems. In particular, we show that techniques from standard multigrid for
anisotropic problems can be adapted to these discretizations on both
tensor-product as well as semi-structured meshes. The resulting methods are
demonstrated to be robust preconditioners for several standard flow benchmarks.
