Mean flow characteristics of a turbulent dual jet consisting of a plane wall jet and a parallel offset jet

Abstract

An exhaustive study is carried out to highlight the flow features arising due to a dual jet consisting of a plane wall turbulent jet and a parallel turbulent offset jet (hereafter this combination is termed as a dual jet). The standard high Reynolds number two equation k–ε model is used to solve the two-dimensional, incompressible, turbulent flow. A detailed analysis is carried out to compare the flow characteristics of the offset jet and the dual jet for an offset ratio between 3 and 15 at an interval of 2. It is noticed that the presence of wall jet in addition to the parallel offset jet has a tremendous effect on the flow characteristics. In the present study, the location of reattachment point and vortex centre of an offset jet and merge point, combined point, and the vortex centres of a dual jet are identified and expressed by correlations which depend on the offset ratio. It is interesting to observe that the cross-stream movement of vortex centre is linear with the change in offset ratio for both kind of jets either an offset jet or a dual jet. However, the streamwise movement of vortex centre follows a parabolic trend with respect to the offset ratio with an exception of combined point which is weakly dependent on the cubic power of offset ratio. The jet half width of a dual jet is compared for different offset ratios by a unique scaling method for which the correlation is also proposed; it is observed that the variation is parabolic with respect to the axial location. The total momentum flux of a dual jet is found to decrease with the increase in the offset ratio as opposed to almost insignificant change in the value for an offset jet. And, the value of integral constant is on the lower side as compared to the corresponding case of either an offset jet or a parallel jet.