有限元法圆射流的气动噪声和模态研究

Aerodynamic Noise and Modal Analysis of Round Jet Based on the Finite Element Method

本文基于有限元的网格模型,采用频域分析的方法研究了圆喷嘴的射流声场,结果表明:圆柱喷嘴的结构模态随管嘴的缩短而基频升高;大雷诺数下的声压在0°至35°的范围,均有较大的指向,总体呈弱的非轴对称结构,而小雷诺数高马赫数的声压指向是轴对称的;在高频部分的下游传递出锥状逆波,破坏了轴线周侧的波阵面,尤其是在上游轴线周侧;以声阻抗率为特性的声传播,呈现测量的退相干性。

Based on the finite element method, the sound field of cylindrical nozzle is analyzed with frequency analysis technology. The main conclusions are as follows： the flmdamental frequency in structure modes of cylindrical nozzle increases as the nozzle shortened; the sound pressures from 0° to 35° have a larger directivity in larger Reynolds Number condition, with weak non-axisylnmetric structure generally, but pressure directivity in the smaller Reynolds Number condition with low Mach number is axisymmetric, the cone wave transmits against the main airflow in high-frequency produced in the downstream part, and it destroys the wavefronts around the side of the axis, especially in the upstream side of the axis, the jet sound propagates based on the characteristics of acoustic impedance rate, and it displays decoherence nature of measurements.