Vortical Structure in Forced Unsteady Circular Jet: Simulation by 3D Vortex Method

Three-dimensional vortex-method simulations are made of a round jet forced by axisymmetric, helical and multiple disturbances. The multiple disturbances are combinations of two helical modes rotating in the opposite direction. The present simulations demonstrate the evolution of large-scale vortex structures in the forced jet. Results of the simulations are in reasonable agreement with available experimental results. 1 Introduction The vortex structure in the developing region of jets plays a crucial role in the production of Reynolds stresses and the jet noise, and in the mixing of the jet fluid with the surrounding fluid. This indicates that the active control of the vortex structure may have wide applications in fluids engineering. Reynolds and Parekh [23] demonstrated that the round jet experiences a dramatically high rate of spreading by appropriate combinations of frequencies of axisymmetric and orbital disturbances. Experiments conducted with the jet forced by two helical modes..