The effect of inflow conditions on the development of non-swirling versus swirling impinging turbulent jets

The results show that in comparison to free jets, the streamwise development of non-swirling impinging jets generally follows their corresponding free jet counterparts up to about x/D = 1 downstream from the nozzle exit plane. In comparison with a non-swirling impinging jet of equal Reynolds number, the introduction of low levels of swirl into an impinging jet results in similar centreline velocity decay but a significant reduction in wall shear stress and turbulent kinetic energy at the wall jet region. The reduction in wall shear stress becomes more pronounced as the swirl number increases. The increase in turbulence intensity at the inlet significantly affects turbulence characteristics of swirl flows in the central impingement region. Within the range of swirl numbers investigated, different inlet swirl profiles do not drastically change the static pressure behaviour on the impingement surface compared to non-swirling jets.