Effect of exit Reynolds number on self-preservation of a plane jet

We investigated in experiment the effect of exit Reynolds number on self-preservation of a turbulent plane jet. Centerline velocity statistics were measured in plane jets issuing from the same nozzle but respectively with seven Reynolds numbers varying between Re = 4582 and Re = 57735 where Re ≡ Uj h/νUj being the momentum-averaged exit mean velocity h the slot height and ν　the kinematic viscosity. All measurements were conducted using single hot-wire anemometry and over an axial distance x of 40　h. These measurements revealed a significant Re-dependence of either the mean or turbulent flow field.　As Re increases the pace of the jet development decreases and as a result both the mean and turbulent properties reach their self-preserving states over a longer downstream distance x.　The centerline integral scale L　for all jets grows linearly with x and the growth rate decreases as Re is increased. It is also found that the local Reynolds number ReL scales with x as ReL∝x1/2. The study suggests that differences of the self-preserving states observed may be related to the differences in the underlying turbulence structures in the near field of the seven jets.