Investigation Of Aerodynamic Noise Sources Identification Technique Based On Microphone Arrays

With rapid development of civilian and military aircraft, researches onaerodynamic noise are attracting more and more attention in the world. TheInternational Civil Aviation Organization (ICAO) revises the noise standard whichrequires a lower level of aircraft noise. For military aircraft, reducing noise canimprove the stealth performance and increase the comfort of the passengers. So it’snecessary to study the aerodynamic noise in the wind tunnel test which is the mosteffective mean of the research. The identification technique about aerodynamic noisesource based on microphone array is the core technology of the wind tunnel test.Therefore, the purpose of this paper is to develop an optimization design methods forthe microphone array and explore advanced algorithms for the identification ofaerodynamic noise source.In Chapter1, the background of aerodynamic noise and three research methodsare introduced. Then the state and trend of development of this problem at home andabroad are reviewed.In Chapter2, the function of array analysis evaluation which explains theresponse of the microphone array is introduced. The performance of severalmicrophone arrays with different arrangement is analyzed and the results show thatthe comprehensive performance is the best with a spirally distribution of themicrophones. In the end, to improve the resolution and increase the dynamic range,the optimization design and calculation for spiral array has been taken using particleswarm optimization algorithm.In Chapter3, the classical beamforming algorithm considering influence of theflow convectivity and the shear layer is introduced. The CLEAN algorithm and theDAMAS algorithm are deduced, and numerical proofs and testing proofs areproceeded. The results show that the CLEAN algorithm can effectively improve theperformance of suppressing side lobes whereas the DAMAS algorithm improves theidentification resolution.In Chapter4, a test of aerodynamic noise source is carried out. A NACA0012airfoil is chosen as the model to design the test scheme and clarify the test method. Itdemonstrates that the correction method of the shear layer is reasonable in windtunnel test. Different configurations, including the wind speeds and attack angles, aretested. The results show that the DAMAS algorithm can effectively identify singlepoint noise source and two separate point sources, but is not suitable for the noise source of the airfoil which is congregate noise source.In the final chapter, the findings are concluded and suggestions are given.