This paper investigates the sound radiation from a rotor near a wall. It has been shown in previous studies that the noise from turbulence ingestion for this configuration does not fully explain the radiated sound spectrum for high thrust conditions. However, it was also shown that the flow in the gap between the blade tip and the wall includes a well defined vortical structure for high thrust cases. The purpose of this paper is to show that the sound radiation at these operating conditions can be modeled by a blade vortex interaction. A simple model for the blade vortex interaction has been developed and the strength of the vortex and its structure have been investigated using PIV measurements. Using the measured parameters in the sound radiation model gives good predictions of the far field sound at the higher blade harmonics. If some adjustments are made to the measured parameters, the predicted levels are improved.
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