Mean-flow and turbulent characteristics of free and impinging jet flows

Numerical solutions are presented of the governing equations for three plane flows: the laminar free jet; the developing turbulent free jet; and the turbulent impinging jet for different ratios h/b of the nozzle height h above the plate to the nozzle width b. The accuracy of the numerical procedure is demonstrated by comparing the solution of the Navier-Stokes equations for the laminar-flow case with their analytical boundary-layer solution. For turbulent flows these equations are solved after Reynolds averaging. Closure is achieved by a two-equation turbulence model in conjunction with three alternative algebraic expressions for the turbulent stresses. The capabilities of such an approach are illustrated by the extent and consistency of the predictions and the satisfactory agreement of the measurable quantities with the more reliable experimental data in the literature. The limitations of the models employed, evident from their lack of universality, are discussed in the light of their derivation from more complex ‘single-point’ closures. Features of the flows studied of interest include: the near-nozzle behaviour of a ‘finite’ laminar free jet; the potential core and transition regions of a turbulent free jet, along with the fully developed similarity profiles; the enhanced heat-transfer characteristics of impinging jet flows; and the similarity of the developing wall jet after impingement to the standard wall-jet configuration.