The influence of tabs on fluid dynamic measurements downstream of a backward-facing step

PIV-method was used to study the flow behind a backward-facing step in the presence of tabs for the Reynolds number Re =4000. The studied tabs had rectangular shape and a height of 6 mm, and were installed with a step of 25 and 50 mm. The tabs, depending on the step, had a different effect on velocity profile. At the tab location, the profiles of the average longitudinal and transverse velocity were strongly deformed and became similar to the behaviour behind the solid rib. In the area between the tabs due to the adjacent pair of tab-induced vortices, the attachment of the mixing layer occurred earlier than at streamlining of a smooth step. The recirculation area was noticeably reduced for tabs with spacing of 50 mm, and at the same time, with a reduction in the distance between them to 25 mm, the size of this zone increased.