Numerical simulation of scalar dispersion downstream of a square obstacle, Part I: Reynolds-averaged Navier-Stokes simulations

The scalar dispersion from a line source downstream of a square obstacle immersed in a fully turbulent boundary layer is investigated by means of Reynolds-Averaged Navier-Stokes simulations. A second-order accurate finite-volume method is employed in the analysis and several turbulence closure, namely the k-epsilon, the k-omega and a Reynolds Stress Transport (RST) model are adopted and compared. The scalar transport is approximated to a passive mechanism and the modeling of turbulent scalar fluxes is based on a constant turbulent Schmidt number. The most interesting result obtained from the RANS-based analysis is that a very accurate prediction of local mean velocity profiles does not represent the key requirement in the scalar dispersion process, which is found dominated by the estimated level of eddy-diffusivity for the scalar