Green's Function Applicable to Turbofan Exhaust Noise in Jets with an External Center-Body

Khavaran, Abbas

关键词: GREEN'S FUNCTIONS;    TURBOFANS;    JET AIRCRAFT NOISE;    FLOW EQUATIONS;    RIGID STRUCTURES;    NUMERICAL ANALYSIS;    DIRECTIVITY;    RAYLEIGH EQUATIONS;   

RP-ID  :  AIAA-2018-3613,GRC-E-DAA-TN57885

学科分类：航空航天科学

美国|英语

来源: NASA Technical Reports Server

【 摘 要 】

The problem of propagation of sound across the shear layer in a turbofan jet exhaust with an external center-body is discussed. The wave equation of interest is compressible Rayleigh equation. Two forms of the equation are considered, and the Green's function solutions subject to appropriate surface conditions on the center-body and flight condition in the ambient are presented. Directivity studied in a heated exhaust at temperature ratio of 2.0 and Mach number 0.90 indicate that a rigid center-body tends to increase the sound propagation at forward angles relative to an exhaust without a center-body, while application of suitable surface liner may significantly reduce this enhancement. A general form of the far-field solution to the propagation equation in a parallel flow under supersonic conditions and in the neighborhood of the shear layer singularity is also discussed.