Dynamics of Hybrid Flow Control in a Boundary-Layer-Ingesting Offset Diffuser

** † * * The effectiveness of hybrid flow control, comprised of tandem arrays of passive (vanes) and active (synthetic jets) control elements for suppression of engine face total-pressure distortion is investigated experimentally. The experiments are conducted in a wind tunnel inlet model with an offset diffuser at speeds up to M = 0.55 using inlet flow conditioning that mimics boundary layer ingestion on a Blended-Wing-Body platform. Time-dependent distortion of the dynamic total pressure field at the AIP is measured using an array of forty total-pressure probes, and the control-induced distortion changes are analyzed using triple decomposition and proper orthogonal decomposition (POD). These data indicate that an array of small-scale synthetic jet vortices merge into two large-scale, counter-rotating streamwise vortices that exert significant changes in the flow distortion. The two most energetic POD modes appear to govern the distortion dynamics in either active or hybrid flow control approaches. Finally, it is shown that the present control approach is sufficiently robust to reduce distortion with different inlet conditions of the baseline flow.