Shadowgraph visualizations of a submerged free slot jet of air

The paper presents flow visualizations, obtained with the shadowgraph technique, of a submerged free slot jet of air in the Reynolds number range allowed by two wind tunnels, i.e. from Re = 7100 to Re = 52900, where the Reynolds number Re is based on the hydraulic diameter of the slot. The shadowgraph visualizations have confirmed the presence of the undisturbed region of flow, which is the zone of the jet flow where velocity and turbulence are similar to those measured on the slot exit, of height H. The length of the undisturbed region of flow, Lu, depends on the Reynolds number and is equal to Lu = 4.4H at the lowest Reynolds number investigated, i.e. Re = 7100, and decreases with the increase of the Reynolds number.