Análise numérica da transição à turbulência em escoamentos de jatos circulares livres

Abstract

The interest in jet flows is justified by their remarkable technological importance in industrial applications, aircraft propulsion systems and noise generation processes. In all these applications, jet control is the key for the optimization of processes or even the solution of specific problems. With this motivation in mind, the present work consists in the physical analysis of free round jets by means of three-dimensional simulations. Besides this goal, analyses of the influence of different types of perturbations on the formation and evolution of turbulent structures are sought. In the first stage of this work, simulations were run using two codes (LAYER2 e CIL3D), which employ Large-Eddy Simulation and 2nd order numerical schemes. The results obtained did not allow the aims proposed to be reached. However, it was possible to conclude that loworder numerical schemes are not suitable for detailed simulations of jet flows. This has been verified in other works as well. From the viewpoint of physical analysis, successful results were obtained by using the code SPECTRAL, with which Direct Numerical Simulations were run using a pseudo-spectral method. The results of these simulations allowed to put in evidence structures and phenomena typical of the flows investigated, as well as to better understand the respective generation mechanisms. The possibility of controlling the jet through the imposition of different perturbations to the initial conditions could also be confirmed. The proximity of the inertial region to the inclination of -5/3 and the decay region were verified in the energy spectra.