A symmetry preserving dissipative artificial viscosity in an r-z staggered Lagrangian discretization

We present an artificial viscous force for two-dimensional axi-symmetric r-z geometry and logically rectangular grids that is dissipative, conserves the z-component of momentum and preserves spherical symmetry on an equi-angular polar grid. The method turns out to be robust and performs well for spherically symmetric problems on various grid types, without any need for problem- or grid-dependent parameters.