An Experimental Study of a Steady Plane Wall Jet with Different Reynolds Numbers, Coflow Stream and Surface Conditions

Abstract

The effects of Reynolds number, coflow stream and surface roughness on a steady two-dimensional wall jet were examined experimentally in an atmospheric boundary layer wind tunnel using a Cobra probe. Five Reynolds numbers in the range 56,500 < Re < 134,000 and five values of coflow velocity/jet velocity ratio ranging from 0.11 to 0.23 were considered. In addition, a 40-grit sheet was used as the rough surface to investigate the effect of surface roughness. The results demonstrate that the Reynolds stress increases with the decrease of slot Reynolds number, and the effects of a higher Reynolds number on the spread of the half-height and the decay of maximum velocity are less pronounced. The coflow and surface roughness have a clear effects on the streamwise development of the half-height and the maximum mean velocity. The coflow significantly decreases the spread rate and the decay of maximum velocity compared with those without coflow, while the surface roughness increases those parameters relative to those on a smooth surface.