Local equilibrium assumption for round jet calculations

The similarity solutions of So and Hwang (1986) for self-preserving incompressible turbulent round jets are used to derive closed-form similarity solutions to the k and epsilon equations, and the effect of the local-equilibrium assumption (LEA) on round-jet computations is evaluated. Numerical results are presented graphically and compared with the experimental data of Wygnanski and Fiedler (1969) and the computational results of Launder et al. (1972) and Vollmers and Rotta (1977). It is found that when the LEA is accounted for, the jet-centerline turbulent kinetic energy k0 decays as 1/x (where x is the axial coordinate), whereas without accounting for LEA it decays as 1/(x squared); 1/x decay is shown to be in better agreement with observations.