IMPLICIT TREATMENT OF COMPLEX BOUNDARY CONDITIONS FOR FULLY COUPLED SOLVERS

Work on improving the robustness and performance of CFD solvers for applications involving complex flow physics has lead an increasing number of developers to adopt the ”fully coupled” approach to resolving the velocity pressure coupling of the Navier-Stokes equations. In the fully coupled algorithm the Momentum and continuity equations are solved as once system of equations allowing for more of the velocity-pressure effects to be accounted for implicitly as opposed to segregated algorithms where much of the coupling is treated explicitly. Fully coupled algorithm have actually long been used in density based solvers, and have since over a decade started to gain more popularity in the OpenFoam and more general CFD community. An essential ingredient for a fully coupled solver is the proper treatment of the boundary conditions, this is quite understandable since a flow problem is defined by the boundary conditions as well as its geometry and flow properties. In this paper we aim to address some of the issues that relate to the implementation of complex boundary conditions in fully coupled solvers for both the incompressible and compressible flow regimes.