运动流体介质和剪切层共同作用下平面近场声全息技术改进

Improvement of planar nearfield acoustic holography under the combined action of moving fluid medium and shear layer

传统的平面近场声全息将全息面置于射流内部。为了降低窗效应和卷绕误差对重建精度的不利影响,一般要求全息面尺寸为声源的2倍以上,而较大尺寸的传声器阵列放在射流内部会干扰射流的稳定。针对这一问题,提出将整个全息面置于射流外部的方法。根据经典的剪切层修正理论,首先分析声波由声源传播至全息面过程中路径和幅值的改变,继而推导出修正后的声场传播公式,最终建立起马赫数小于0.3的运动流体介质和剪切层共同作用下的平面近场声全息理论模型。数值仿真表明,改进后的平面近场声全息技术能够得到高分辨率的重建声场,对气动噪声源的定位精度较高,并且具备一定的抗干扰能力。

Traditional planar nearfield acoustic holography places the hologram inside the jet.In order to reduce the adverse effect of window effect and wraparound error on reconstruction accuracy,it is generally required that the hologram size is twice more than that of the sound source,while larger microphone array placed inside the jet will interfere with the stability of the jet.To solve this problem,it was proposed to place the entire hologram outside the jet.According to the classical shear layer correction theory,the changes of path and amplitude of sound wave propagating from sound source to hologram were analyzed.Then the modified sound field propagation formula was derived.Finally,the theoretical model of planar nearfield acoustic holography under the combined action of moving fluid medium with the Mach number below 0.3 and shear layer was established.Numerical simulations show that the improved planar nearfield acoustic holography leads to reconstructed acoustic fields of high resolution,with high localization accuracy of aerodynamic noise source and certain anti-interference ability.