Abstract:

The thickness noise of helicopter rotors and the numerical prediction method of the acoustic pressure time history of this noise are studied .The analysis is based on the collapsing sphere equation developed by Farassat.The following two problems are detailed. (1)The effect of numerical error on the prediction results of thickness noise. Based on the numerical analysis, it was found that to obtain the correct acoustic pressure signature, the significant digits of the variables in the calculation equation must be larger than 15,and the numerical integration must be dealt with carefully. (2) The variation feature of the acoustic pressure signature of helicopter thickness noise with the helicopter rotors geometry and motion parameters.Based on the numerical calculation, some valuable results are obtained for the control of the helicopter thickness noise.

Key words: noise　helicopter rotors, aircraft noise, aeroacoustics