Turbulent jets issuing from the rectangular nozzle with a rectangular notch at the midspan

The mean velocity field of turbulent air jets issuing from a rectangular nozzle (AR: Aspect Ratio-12.5) with a rectangular notch at the midspan have been investigated experimentally. The four notch aspect ratios (NAR) of the rectangular notch perpendicular to the rectangular nozzle axis are 2.5, 7.5, 12.5 and 165. The purpose of this study is to examine the possibility of manipulating the mean velocity field of the rectangular jet using the rectangular notch as a passive disturbance. In this experiment, it is revealed that the inward secondary flow velocities towards the jet centre region on both the rectangular jet axis and the rectangular notch axis in the upstream region are found in all NAR cases, and both the magnitude and the direction of the secondary flow velocity depend on the value of NAR. Furthermore, the potential core length of NAR=12.5 takes the largest value in all NAR cases. The half velocity width on the rectangular jet axis takes the minimum value for NAR=165.