This model implements Navier-\/\-Stokes flow of a single fluid. By default, it solves the momentum balance of the time-\/dependent Stokes equations, i.\-e. \[\frac{\partial\left(\varrho\,\mathbf{v}\right)}{\partial t}+\boldsymbol{\nabla} p -\nabla\cdot\left(\mu\left(\boldsymbol{\nabla}\mathbf{v}+\boldsymbol{\nabla}\mathbf{v}^T\right)\right)-\varrho\,\mathbf{g}=0\;, \] and the mass balance equation \[\frac{\partial\varrho}{\partial t}+\nabla\cdot\left(\varrho\,\mathbf{v}\right)- q =0\;. \]
If the property {\ttfamily Enable\-Navier\-Stokes} is set to {\ttfamily true}, an additional convective momentum flux term (Navier term) gets included into the momentum conservation equations which allows to capture turbolent flow regimes. This additional term is given by \[\varrho\left(\mathbf{v}\cdot\boldsymbol{\nabla}\right)\mathbf{v}\;. \]
These equations are discretized by a fully-\/coupled vertex-\/centered finite volume (box) scheme in space and using the implicit Euler method in time. Be aware, that this discretization scheme is quite unstable for the Navier-\/\-Stokes equations and quickly leads to unphysical oscillations in the calculated solution. We intend to use a more appropriate discretization scheme in the future, though.
