Broadband haystacking noise results from the correlated unsteady loading of successive blades due to ingested turbulence. This noise can therefore be predicted with knowledge of the turbulent inflow and blade response function, but this is not trivial, especially for complex flows which are inhomogeneous and anisotropic. This paper details the noise and direct measurement of the unsteady upwash correlation from the rotating frame of a 10-bladed 457 mm diameter rotor immersed in two planar wall boundary layers of varying thickness at non-thrusting and thrusting advance ratios. At low thrust conditions, the measured upwash correlation can be predicted using the fixed frame space-time correlation function. However, as the thrust is increased the predictions progressively deviate from measurement most likely due to the formation of a separation region generated on the wall beneath the rotor. Surprisingly, this produces haystacking-like behavior in rotor-frame measurements of the blade-to-blade upwash correlation at spanwise locations near the blade tips. A lateral contraction of the turbulence is not observed in measurement of the spanwise coherence with increasing thrust. Finally, the spectral peaks in the radiated noise increase with the boundary layer thickness by similar ratios at low thrust conditions. For high thrust, the peaks in the broadband noise have the same approximate magnitude.
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