  Entropy stable schemes ensure that physically meaningful numerical solutions
also satisfy a semi-discrete entropy inequality under appropriate boundary
conditions. In this work, we describe a discretization of viscous terms in the
compressible Navier-Stokes equations which enables a simple and explicit
imposition of entropy stable no-slip (adiabatic and isothermal) and reflective
(symmetry) wall boundary conditions for discontinuous Galerkin (DG)
discretizations. Numerical results confirm the robustness and accuracy of the
proposed approaches.
