A COMPARISON WITH THEORY OF PEAK-TO-PEAK SOUND LEVEL FOR A MODEL HELICOPTER ROTOR GENERATING BLADE SLAP AT LOW TIP SPEEDS

Mini-tuft and smoke flow visualization techniques have been developed for the investigation of model helicopter rotor blade vortex interaction noise at low tip speeds. These techniques allow the parameters required for calculation of the blade vortex interaction noise using the Widnall-Wolf model to be determined. The measured acoustics are compared with the predicted acoustics for each test condition. Under the conditions tested it is determined that the dominating acoustic pulse results from the interaction of the blade with a vortex 1 one quarter revolutions old at an interaction angle of less than 8 degree . Variation of input parameters within the range of the experimental measurements produces agreement between the predicted and measured peak-to-peak pressures when the blade passes close to the vortex at a small interaction angle.

A COMPARISON WITH THEORY OF PEAK-TO-PEAK SOUND LEVEL FOR A MODEL HELICOPTER ROTOR GENERATING BLADE SLAP AT LOW TIP SPEEDS Academic Article