Mean Flow and Turbulence Nonuniformity Downstream of a Turbulence Grid

Extensive measurements are presented downstream of a turbulence grid in the form of a commercially available perforated metal plate. The decay of the Free Stream Turbulence (FST) with streamwise distance follows the behaviour reported by Comte-Bellot & Corrsin [1]. However there is also considerable Free Stream Nonuniformity (FSN) on a scale much larger than the mesh size of the grid. The FSN is associated with small local variations in the open–area ratio and it persists for large streamwise distances. The competing adverse effects of FST and FSN on a Blasius boundary layer are considered