Effect of perforated plates on wide-angle diffuser-exit velocity profiles

In the absence of any flow control, the flow through a wide-angle diffuser consists of a narrow axial jet surrounded by regions of separated flow which persists downstream. The incorporation of perforated plates has a considerable influence on the flow properties within the diffuser. A single perforated plate of 50% porosity simply increases the cross-section of the jet and reduces the size of the separated flow region, whereas in multiple perforated plate combinations more fundamental changes take place. It is shown, for example, that the jet can be displaced from its axial position to a region in close proximity to the wall downstream of the final perforated plate. The properties of this wall-jet are varied as a consequence of changing the location of the multiple perforated plates. © 1990