Effects of nozzle orientation and spacing on flow characteristics of twin rectangular jets

Abstract

The effect of the nozzle orientation and the nozzle spacing on the flow characteristics of twin rectangular jets were studied experimentally. The nozzle spacing ratio S/de of a rectangular nozzle with an aspect ratio of 2 was varied from 2.75 to 6.875. Two nozzle orientations were tested, i.e., twin nozzles oriented along the minor plane (TwinMinor) and twin nozzles oriented along the major plane (TwinMajor), and the results were compared with a single round jet, a single rectangular jet, and a twin round jet. In each case, the Reynolds number based on the maximum jet velocity and the equivalent diameter was 1.5 × 104. The nozzle orientation has no influence on the flow characteristics of twin rectangular jets along the jet centerline. However, the velocity and turbulence intensity of the twin rectangular jets of TwinMajor increases more than that of TwinMinor near the symmetry line of the twin jets, and the location of the combined point (CP) becomes upstream. The twin rectangular jets with a small nozzle spacing ratio, i.e., S/de = 2.75 merge upstream. The velocity near the jet centerline in downstream becomes relatively higher compared to that with a large spacing ratio. The vortex shedding frequency of the twin rectangular jets depends on the nozzle spacing ratio. The flow characteristics of the twin rectangular jets with a large nozzle spacing ratio, i.e., S/de = 5.5 and 6.875 are similar to the single rectangular jet.

Keywords

• rectangular jet
• twin jets
• nozzle orientation
• nozzle spacing
• axis-switching
• hot-wire anemometer