REYNOLDS STRESS DESCRIPTION OF OPPOSED AND IMPINGING TURBULENT JETS .2. AXISYMMETRICAL JETS IMPINGING ON NEARBY WALLS

The flow arising from an axisymmetric turbulent jet with an exit plane in close proximity to the wall against which it impinges is analyzed. The reciprocal of a Reynolds number based on the kinematic viscosity adds here to the two parameters identified in Part I [Phys. Fluids A 5, 203 (1993)] as determining the flow characteristics of two opposed jets, namely the ratio of the turbulence scale to the separation of the jet exit from the wall and the ratio of the turbulence intensity to the mean exit velocity. With all three of these parameters suitably small there is indicated an asymptotic analysis which describes separately the flow in three distinct regions. The temperature of the impinging fluid is assumed to be slightly different from that of the wall so that the mean velocity components, the mean temperature, and the various Reynolds stresses and fluxes vary within a thin wall layer which consists of a viscous sublayer and a turbulent shear layer. When the Reynolds number is suitably high, the sublayer accounts for all of the change in the mean radial velocity and in the mean temperature. The analysis of the turbulence external to the wall layer is compared with experimental data on a turbulent jet impinging on a wall. Agreement with respect to the mean axial velocity and the intensities of the axial and radial velocity components is quite satisfactory. Comparison is made with experimental data on heat transfer to the wall; the predicted dependence of Nusselt number on Reynolds number is confirmed.