## SIMULATION AND COMPARISON OF VARIABLE DENSITY ROUND AND PLANE JETS
## AbstractLarge-eddy simulations of plane and round variable density jets, as well as direct numerical simulations of plane jets were conducted using a variety of density ratios ρ to the freestream density _{j}ρ. The initial momentum flux was kept constant for better comparison of the resulting data. Both simulations confirm experimental results, in that the jet half-width grows linearly with streamwise coordinate _{co}x and the lighter jets decay
much faster than the heavy ones. The centerline velocity
decay is however different between the plane and round geometries. Whereas the round jets exhibits a decay with 1/x for all density ratios, there seem to be two self-similar scalings in plane jets, in the limit of small and large density ratios. In the limit of small density ratios or incompressible flow, U scales as _{c}U ~ 1/√_{c}x, for strongly heated jets on the other hand we find U ~ √(_{c}ρ)) ~ 1/_{co}/(xρ_{c}x. Using nondimensional values for x and U (Chen and Rodi [1980]) collapses the round jet data. Furthermore, the streamwise growth in mean density or the decay of the velocity fluctuations in the self-similar region is stronger for round jets. The round jet simulation with a density ratio of _{c}s = 0.14 shows
additionally a global instability, whose frequency agrees excellently with experimental data. |

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