Characteristics of shear-layer flow field of open-jet wind tunnels

Simplified theoretical formulae for the calculation of the axial and the transversal speeds of open-jet flow were presented. And the effects of two control parameters, ie, the offset parameter and the spreading rate, on the speed profile were analyzed. Experimental studies were performed in two wind tunnels respectively. The distributions of shear-layer speed profile, shear-layer thickness, turbulence intensity and turbulence spectrum were obtained. And the obtained data were compared with theoretical predictions. Results indicated that: beyond a distance from the nozzle, the axial speed profile was strongly self-similar, while the transversal speed profile was weakly self-similar; the shear-layer thickness linearly increased with stream-wise distance; the turbulence intensity was small and stable in the core flow region, slowly but linearly increased in the fully developed region, and rapidly increased in the shear-layer region; the shear-layer turbulence spectrum was broadband, no peaks can be identified in the spectrum.