Author(s): Panayotis C. Yannopoulos
Linked Author(s): Panayotis Yannopoulos
Keywords: Buoyant jet interaction, turbulent jets/plumes, mean flow properties, superposition method, linear/rosette-type outfall
Abstract: The mean flow and mixing properties of single and interacting round vertical turbulent buoyant jets issued in calm and uniform ambient environment have been determined by employing an advanced integral model (AIM), which uses composite profile functions for the transverse distributions of mean axial velocities and mean concentrations. The groups of N = 2, 5, 11 and 25 buoyant jets issued from equally spaced nozzles of equal diameter, located in horizontal series, and the groups of N = 3, 6, 12 and 24 buoyant jets issued from rosette-type formations have been solved. Two values of initial densimetric Froude number have been taken: 2. 5 (plume-like) and 25 (jet-like). The half spacing between adjacent nozzles has been taken equal to the nozzle diameter. Then, the centreline and transverse distributions of velocities have been used to calculate the mean kinetic energy flux. The variations of maximum axial velocities and concentrations in buoyant jet cross-sections are plotted in diagrams versus the longitudinal distance, along with their asymptotes. In the same diagrams the semi-empirical expressions valid for plane/round plumes/jets are given for comparison. The effect of interacting buoyant jets on the mean kinetic energy flux is investigated in the whole buoyancy region and special care is paid on the asymptotic behaviour in the plume-like and jet-like cases. It was found that the variation of the kinetic energy flux is actually identical (all curves coincide practically to each other) for interacting plumes independent from their number and group formation. This behaviour implies self-similarity occurrence in plumes, while the constant divergence of the mean kinetic energy flux along the main flow direction indicates the application of the superposition method. For jets, it is observed that the kinetic energy flux variation differs significantly among the groups and especially from the variation of the plane jet
Year: 2017