Large eddy simulation of a 3-D spatially developing turbulent round jet

A three-dimensional large eddy simulation (LES) of a spatially developing round jet is carried out in cylindrical coordinates using a dynamic subgrid model with strong inflow instability. Evolutions of large-scale vortex structures represented by tangential vortices are obtained and compared with flow visualization. Also presented are three-dimensional spatial evolutions of coherent structure, which are of quasi two-dimensional Kelvin-Helmholtz instability and vortex rings as well as breaking up of the vortex rings with fully three-dimensional characteristics. Predicted results of mean velocity and turbulent intensity agree well with experiments. They are also compared with the results predicted by LES using standard Smagorinsky model and show good self-similarity. Turbulence spectrum of the predicted velocity shows the −5/3 decay for higher wave number, as expected for turbulent round jet flows. In addition, β-test and γ-test are carried out for the instantaneous velocity, showing that the present LES method can successfully predict the hierarchical structure of round jet.