Experimental investigation of interactions of three co-planar and converging jets

Abstract

This experimental study focused on the structures of the flow produced by a novel configuration of three co-planar circular and neutrally buoyant pipe jets. The configuration presented in this paper was symmetrical about the central jet, with both side jets set at an inclined angle of 30° towards the central jet. These three jets discharged into a tank of still receiving water. The flow fields were captured using a particle image velocimetry system, and the complex flow patterns on two orthogonal planes (in-plane and normal to the central jet flow direction) were analysed and characterised in terms of velocity and vorticity distributions. Based on the findings of the study, it was deduced that the centreline velocity of the combined jet exhibited a preserved core before a longitudinal distance of 12D (D is the jet diameter) from the pipe exit and then decayed linearly until 17D. After 17D, the in-plane velocity profile followed a Gaussian distribution, while the profile in the normal plane portrayed a double-peak distribution. Finally, the dynamic interactions among the three converging jets were illustrated through a time series of instantaneous flow fields.