LAUSR

Summary Determining boundary conditions for incompressible flows is such a delicate matter that affects the accuracy of the results. In this research, a new characteristic based boundary condition for incompressible Navier–Stokes equations is introduced. Discretization of equations has been done via finite volume. Additionally, artificial compressibility correction has been employed to deal with equations. Ordinary extrapolation from inner cells of a domain was used as a traditional way to estimate pressure and velocities on solid wall and inlet/outlet boundaries. Here, this method was substituted by the newly proposed boundary conditions based on the characteristics of artificial compressibility equations. To follow this purpose, a computer code has been developed to carry out series of numerical tests for a flow over a backward facing step and was applied to a wide range of Reynolds numbers and grid combinations. Calculation of convective and viscous fluxes were done using Jameson's averaging scheme. Employing the characteristic based method for determining boundary conditions has shown an improved convergence rate and reduced calculation time comparing with those of traditional ones. Furthermore, with the reduction of domain and computational cells, a similar accuracy was achieved for the results in comparison with the ones obtained from the traditional extrapolation method and these results were in good agreement with the ones in the literature.