Fluidic Control of the Flow within a Diffuser with Variable Bend

A flow control approach to address total pressure distortions at the AIP of a modular diffuser testbed with a variable bend section (20    60o, 0.2  r/D  0.5) was developed and tested in a joint experimental/numerical study. In this approach, fluidic actuation that is applied downstream of the interchangeable bend configurations is devised to counter the transport of streamwise vorticity concentrations of opposite sense along the bend’s inner radius surface that subsequently roll into counter rotating vortices, are advected through the diffuser to the AIP, and induce total pressure deficit and distortion. Experimental and numerical investigations of the control approach that utilized spanwise arrays of yawed wall jets demonstrated successful suppression and delay of vorticity transport within the diffuser within 0.3  M  0.5. It is shown that a single wall jet array downstream of the bend can effectively reduce distortion and improve recovery across bend geometries at bend angles and radii up to 60o and down to 0.2D, respectively, reducing the baseline distortion level by 55% at thrust-based momentum coefficient \mathbit{C}_\mathbit{\mu}^\mathbit{F}\ = 0.02. Moreover, optimization of the number of active jets can further reduce the baseline distortion by 60% at \mathbit{C}_\mathbit{\mu}^\mathbit{F}\ = 0.014 when only 60% of the original jet array is active.