Effect of plume meandering in modeling dispersion downstream a wall-mounted cube using the RANS equations

摘要

A DNS database is employed to examine the onset of plume meandering downstream of a wall-mounted cube and to address the impact of large-scale unsteadiness in the modeling of dispersion using the RANS equations. The cube is immersed in a uniform stream where instabilities in the thin boundary-layer developing over the flat plate are responsible for inducing vortex-shedding in the wake of the obstacle. Spectra of velocity and concentration fluctuations computed from the direct simulation exhibit a dominant frequency immediately downstream of the mean reattachment length. The onset of periodic fluctuations with opposite phase is confirmed by pronounced negative values of the correlation coefficient in the same region. Unsteady RANS simulations performed with the v~2 - f model show a remarkable improvement against the steady-state solution in predicting the statistical properties of the plume in the far-field, where the decay of maximum concentration and the plume width are found in closer agreement with DNS data when unsteady simulations are performed.