前缘直板扰流对高速空腔的降噪效果分析

高速空腔复杂流动和噪声一直是航空航天领域所关注的问题，高强度的空腔噪声不仅影响腔内仪器设备的正常运行，还会对其自身的结构产生疲劳破坏，进而影响飞行器的飞行安全和品质，因此空腔噪声的抑制研究和典型控制方法的降噪效果分析对提高飞行器结构安全性意义重大。本文通过开展高速风洞试验研究跨超声速（Ma=0.9和Ma=1.5）来流条件下前缘直板装置对空腔（长深比为6）流动和噪声的控制机理，通过对比多种前缘直板控制条件下的腔内噪声声压级（SPL）分布，确定直板控制参数的优化选择方法及最优参数；利用静态/动态压力传感器和油流试验采集腔内静压、脉动压力和壁面流谱，着重分析前缘直板对腔内流动结构、声压级和声压频谱的影响规律。结果表明：前缘直板可以大幅度抬高剪切层的位置，使得后缘的撞击区域后移，从而削弱流体进入腔内的流量和强度；可以有效降低腔内静压、减小回流强度和范围，对腔内声压级和峰值噪声也具有显著的抑制效果，Ma=0.9和Ma=1.5时后缘声压级降低幅值可达11.13 dB和8.0 dB。前缘直板流动控制为高速来流条件下空腔噪声的抑制提供了一种新的方法，可有效应用于飞行器上空腔结构的流动/噪声控制，具有重要的工程应用价值和前景。

Effect of leading edge plate on high speed cavity noise control

Cavity noise caused by the high speed airflow has been paid much attention to in the field of aerospace, as it not only affects normal operation of equipment inside the cavity, but also threatens the structural strength and safety of aircraft. Therefore, the study of cavity noise suppression has important significance in improving the safety of aircraft. Effects of leading edge plate on the flow and noise of the cavity model (the ratio of length to depth is 6) at the flow velocity of Ma=0.9 and of Ma=1.5 are investigated with high speed wind tunnel experiment. Sound Pressure Level (SPL) distribution and spectral characteristics of sound pressure of the noises in the cavity with leading edge plates of different parameters are compared to define the selection method and optimal parameters of the plate. The acoustic and flow field information in the cavity are obtained with the dynamic/static pressure measurement and oil flow experiment. The oil flow patterns of the surfaces and pulsating/static pressure inside the cavity are discussed, and the effect of the leading edge plate on the static pressure, flow structure, sound pressure level and sound pressure spectrum are analyzed. The results show that the leading edge plate can greatly lift the shear layer, raise the impact position on the back wall area, and reduce the flux rate and intensity in the cavity. By controlling the leading edge plate, the static pressure and backflow area are effectively suppressed and the SPL and peak noise also fall down significantly, with the SPL at the aft edge decreasing by 11.13 dB at Ma=0.9 and by 8.0 dB at Ma=1.5. The leading edge plate provides a new method for cavity noise suppression in high-speed flow condition, which can be effectively applied to flow/noise controlling of cavity structure on aircraft, and has important engineering application value and prospect.