COMPUTATION OF TURBULENT AXISYMMETRICAL AND NONAXISYMMETRIC JET FLOWSUSING THE KAPPA-EPSILON MODEL

It is known that the standard K-epsilon model does not provide an accu rate prediction of the mean how of turbulent jets. This is so even whe n the Pope and Sarkar correction terms are included, It is suggested t hat the K-epsilon model, together with the Pope and Sarkar terms for n onplanar and high convective Mach number flow corrections, does contai n the essential ingredients of turbulence physics for adequate jet mea n flow prediction. The problem lies in the standard coefficients that were calibrated by using boundary-layer and low Mach number plane mixi ng layer data. By replacing these coefficients by a new set of empiric al coefficients? it is demonstrated that the model can offer good pred ictions of axisymmetric, rectangular, and elliptic jet mean flows over the Mach number range of 0.4-2.0 and jet total temperature to ambient temperature ratio of 1.0-4.0. The present result conveys the message that it is possible that there is no universally applicable turbulence model. The reason is that although the characteristics and dynamics o f fine-scale turbulence may be the same for all turbulent hows, the la rge turbulence structures, having dimensions comparable to the local l ength scale of the how are significantly influenced by local boundary conditions and geometry. Thus overall turbulence dynamics are somewhat problem type dependent.