Abstract:

Large eddy simulations of a three dimensional spatially developing mixing layer are conducted to investigate the origin of the vortex structure of the mixing layer and its evolution to different inlet initial disturbances. The coherent structure, such as the spanwise vortices(rollers), the pairing of the rollers(i.e. co rotation and amalgamation of neighboring rollers) and the secondary streamwise vortex structure have been observed in the present simulation. These results suggest that there is an inherent relation between the large scale vortex structure and the inlet initial disturbances. A transition to turbulence triggered by vortices tearing has also been observed. The mechanisms responsible for the growth of three dimensionality and onset of transition to turbulence lay the foundations of controlling the evolution of the mixing layer.

Key words: mix ing lay er, coherent str uct ur e, m ix ing tr ansition, lar ge-eddy simulatio n