Boundary Layer Ingestion

    We are studying the ingestion of large turbulent structures by a thrusting rotor. Specifically, we are considering the interaction between a thick two-dimensional shear flow, in the form of a boundary layer or wake, and a rotor. This interaction produces correlated unsteady loads on the blades and haystacks in the acoustic spectra. This interaction is complex as the rotor distorts the inflow on approach changing the unsteady upwash and forces as well as the acoustic directivity.
    In this project, we have used on-blade instrumentation to directly measure the unsteady upwash experienced by blades at various thrusting conditions, PIV for spatial measurements of the instantaneous and time-averaged flow around the rotor, and microphones and microphone arrays to measure the noise.

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Ingesting the Wake of a Cylinder

Cylinder upstream of rotor

Rotor directivity model

Measured acoustic spectra