Abstract:
The non-modal spatial development of stationary three-dimensional perturbations in a circular flooded jet at Re = 2850 is numerically investigated. The conditions of the laboratory experiment performed earlier at the Moscow State University Research Institute of Mechanical Engineering are reproduced. A method of calculation of optimal perturbations in the conditions of the main flow developing downstream is developed. The optimal perturbations corresponding to different azimuthal numbers are found. Their shape, character of development and degree of growth are determined. Nonlinear development of optimal perturbations at different values of their initial amplitude is studied. It is shown that nonlinear effects lead to a slowing down of the growth rate when they develop downstream. Currents deformed by stationary perturbations in the angular direction are investigated for stability to small unsteady perturbations. It is found that with increasing degree of deformation, the maximum growth rate of perturbations increases significantly due to the appearance of a specific short-wave mode of instability.
