Investigation of the Vortex Picture of a Free Jet Flow Bounded by Flat Walls

Abstract

It is shown that the aerodynamics of turbulent jets flowing from rectangular nozzles is significantly influenced not only by the presence or absence of limiting end walls, but also by the development of large-scale coherent vortices formed at the initial section of the jet. It is established that in the case of large-scale vortices formed at the initial section with axes parallel to the free edge of the nozzle, they can either rest against the end walls with their ends, or close on themselves at the end walls, covering the initial section of the jet. It is shown that the initially formed annular vortices covering the initial section of the jet deform as they move away from the nozzle and turn into vortex cords with axes parallel to the direction of the jet. As a rule, the vortex cords are arranged symmetrically relative to the axis and have opposite directions. These vortices are the main cause of the appearance of an uneven velocity and temperature profile along the axis. At the same time, large-scale primary vortices with their ends rest against the end walls and cannot cause the appearance of maxima and minima of the velocity profile along the axis. In this case, the development of the boundary layers at the end walls is similar to the development of the boundary layer of a homogeneous flow in a flat channel.