Experimental study of the turbulence ingestion noise of rotor blades

In this work, we experimentally investigate turbulence ingesting rotor noise under various thrusting states. The broadband noise caused by turbulence ingestion is found to dominate at the normalized frequency range of $f\phantom{\rule{0}{0ex}}R/{U}_{\mathrm{\ensuremath{\infty}}}$ = 20 to 80 when the rotor is under low-thrusting conditions. Results also suggest that the turbulence ingestion broadband noise can be scaled by Mach number scaling of ${M}_{\mathrm{\ensuremath{\infty}}}^{2}$${M}_{c}^{4}$, where ${M}_{\mathrm{\ensuremath{\infty}}}$ is the freestream Mach number, and ${M}_{c}$ is the corresponding blade tip Mach number.