@TechReport{ it:2006-026, author = {Jan Nordstr{\"o}m and Ken Mattsson and Charles Swanson}, title = {Boundary Conditions for a Divergence Free Velocity-Pressure Formulation of the Incompressible {N}avier-{S}tokes Equations}, institution = {Department of Information Technology, Uppsala University}, department = {Division of Scientific Computing}, year = {2006}, number = {2006-026}, month = may, abstract = {New sets of boundary conditions for the velocity-pressure formulation of the incompressible Navier-Stokes equations are derived. The boundary conditions have the same form on both inflow and outflow boundaries and lead to a divergence free solution. Moreover, the specific form of the boundary conditions makes it possible derive a symmetric positive definite equation system for the internal pressure. Numerical experiments support the theoretical conclusions. } }